Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 02/25/07

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
400 AM PST FRI FEB 23 2007 .SYNOPSIS... MOIST UNSTABLE AIR WILL CONTINUE SHOWERS AND ISOLATED THUNDERSTORMS THIS MORNING...DECREASING THIS AFTERNOON...AND ENDING TONIGHT. GUSTY WINDS IN THE MOUNTAINS AND DESERTS WILL DECREASE THIS EVENING. FAIR AND WARMER SATURDAY UNDER WEAK HIGH PRESSURE. COOLER AND BREEZY SUNDAY WITH SOME CLOUDS AS A LOW PRESSURE SYSTEM MOVING THROUGH NORTHERN CALIFORNIA BRINGS AN INCREASE IN THE ONSHORE FLOW. CONTINUED BREEZY AND COOLER AT TIMES THROUGH THE MIDDLE OF NEXT WEEK WITH A SLIGHT CHANCE OF PRECIPITATION TUESDAY AND WEDNESDAY. FAIR AND A LITTLE WARMER FOR THE END OF NEXT WEEK. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TODAY THROUGH SUNDAY)... LOWER PRESSURE TROUGH OVER CALIFORNIA AND NEVADA WILL CONTINUE TO MOVE EASTWARD TODAY. THE COLD FRONT MOVED THROUGH SOUTHWEST CALIFORNIA LATE THURSDAY AFTERNOON AND EARLY THURSDAY EVENING AS EXPECTED...BUT WITH RAINFALL A LITTLE LESS THAN EXPECTED. RAINFALL WITH THE FRONT GENERALLY RANGED FROM ONE QUARTER INCH AT THE COAST TO ONE HALF INCH ON THE COASTAL SLOPES...EXCEPT UP TO AROUND AN INCH ON THE COASTAL SLOPES OF THE SAN BERNARDINO MOUNTAINS AND UP TO ONE AND ONE HALF INCHES IN THE SANTA ANA MOUNTAINS. SATELLITE IMAGERY AND RADARS SHOW SCATTERED TO NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS IN THE BROAD CYCLONIC FLOW OVER THE COASTAL WATERS. THESE SHOWERS AND ISOLATED THUNDERSTORMS WILL MOVE ONSHORE THIS MORNING WITH INCREASING COVERAGE AND INTENSITY THROUGH SUNRISE. SHOWERS WILL SLOWLY DECREASE THIS AFTERNOON AND END FROM THE NORTHWEST TONIGHT. GREATEST COVERAGE AND AMOUNTS TODAY ARE EXPECTED ACROSS SAN DIEGO COUNTY. MOST AREAS WILL RECEIVE ONE QUARTER INCH OR LESS TODAY...BUT LOCAL AMOUNTS TO AROUND ONE HALF INCH ARE POSSIBLE FROM HEAVIER SHOWERS OR THUNDERSTORMS OR WHERE SHOWERS REPEATEDLY TRACK ACROSS THE SAME AREA. IN THE MOUNTAINS...ACARS SOUNDINGS AND SURFACE REPORTS SUPPORT SNOW LEVELS AROUND 3500 FEET...OR LOCALLY LOWER IN HEAVIER SHOWERS AND ISOLATED THUNDERSTORMS. WINTER WEATHER ADVISORY CONTINUES UNTIL NOON FOR THE MOUNTAINS. STRONG ONSHORE FLOW WILL BRING GUSTY WINDS TO THE MOUNTAINS AND DESERTS TODAY...DECREASING THIS EVENING. WEAK RIDGING WILL BRING DRYING...WEAKER WINDS...AND MINOR WARMING ON SATURDAY. A SHORTWAVE MOVING INLAND ACROSS NORTHERN CALIFORNIA SUNDAY WILL BRING A RETURN OF STRONGER ONSHORE FLOW...BRINGING COOLING...SOME CLOUDS...AND GUSTY WINDS IN THE MOUNTAINS AND DESERTS. && .LONG TERM (MONDAY THROUGH THURSDAY)... LOWER CONFIDENCE FORECAST WITH REGARD TO THE DETAILS. GLOBAL MODELS SHOW BROAD...WEAKLY CYCLONIC...WEST NORTHWEST FLOW PATTERN ACROSS THE EASTERN PACIFIC AND WESTERN STATES. ECMWF HAS SHOWN THE MOST CONSISTENCY WITH THIS PATTERN AND IS WEAKLY PREFERRED. THIS PATTERN SHOULD KEEP TEMPERATURES ACROSS SOUTHWEST CALIFORNIA A LITTLE BELOW SEASONAL AVERAGES WITH GUSTY WINDS IN THE MOUNTAINS AND DESERTS AT TIMES. THERE`S ALSO A SLIGHT CHANCE OF MAINLY LIGHT PRECIPITATION TUESDAY INTO WEDNESDAY. WEAK RIDGING MAY BUILD ALONG THE WEST COAST LATE IN THE WEEK WITH WEAKER WINDS AND A LITTLE GREATER WARMING. && .AVIATION... FRONT HAS WEAKENED AND MOVED EAST. SOME SHOWERS WILL MOVE THROUGH THE AREA TODAY. SLIGHT CHANCE THUNDERSTORMS. BASES ABOUT 2-3K FT MSL WITH SHOWERS OTHERWISE SCATTERED CLOUDS. VFR VIS WITH ISOLD MVFR WITH SHOWERS. SKIES SHOULD MOSTLY CLEAR LATER THIS AFTERNOON THROUGH TONIGHT. A WEAK SYSTEM IS FORECAST TO MOVE TO THE NORTH LATE SAT BUT IT MAY INCREASE THE MARINE LAYER SAT NIGHT. WINDS AT 5K FT... NORTHWEST 25-30 KT...BECOMING NORTHWEST 15-20 KT AFTERNOON... BECOMING NORTHEAST TO EAST 5-10 KT SAT MORNING. WINDS AT 10K FT... NORTHWEST 35-45 KT...BECOMING NORTH 25-35 KT TONIGHT...BECOMING NORTH 15-25 KT SAT MORNING. && ...MARINE... STRONG WINDS WILL DECREASE THIS AFTERNOON. WINDS WILL INCREASE AGAIN SUNDAY AFTERNOON THROUGH THE NIGHT. STEEP NORTHWEST SWELL WILL INCREASE INTO THE OUTER WATERS TODAY WITH LITTLE CHANGE SATURDAY... DECREASING SUNDAY. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...WINTER WEATHER ADVISORY UNTIL NOON PST TODAY FOR RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY MOUNTAINS-SAN DIEGO COUNTY MOUNTAINS. WIND ADVISORY UNTIL 6 PM PST THIS AFTERNOON FOR COACHELLA VALLEY-SAN DIEGO COUNTY DESERTS. WIND ADVISORY UNTIL 10 PM PST THIS EVENING FOR APPLE AND LUCERNE VALLEYS. PZ...SMALL CRAFT ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR COASTAL WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER AND OUT 30 NM-WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND. && $$ PUBLIC...MARTIN AVIATION/MARINE...WHITLOW NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION...UPDATED
NWS UPTON NY
1005 AM EST FRI FEB 23 2007 .NEAR TERM /THROUGH TONIGHT/... CLOUDS STARTING TO BREAK UP...AND WINDS PICKING UP AS WELL. LOOKING AT ACARS SOUNDINGS...THINK GUSTS TO NEAR 30 KTS A GOOD POSSIBILITY THIS AFTERNOON GIVEN LAPSE RATES AND OBSERVED WINDS ALOFT. TEMPERATURES HAVE BEEN FALLING...A BIT LATER THAN I WOULD HAVE THOUGHT...AND READINGS SHOULD NOT GET MUCH HIGHER THAN THEY ARE THIS MORNING...MAYBE A FEW DEGREES. FOLLOWED LAV GUIDANCE FOR NEAR TERM GRID UPDATES AS DEW POINTS SHOULD DROP SHARPLY. WINDS PERSIST TONIGHT UNDER PARTLY CLOUDY SKIES AS THE STORM DEPARTS. NO CHANGES TO EARLIER DATABASE FOR THE OVERNIGHT. && .SHORT TERM /SATURDAY THROUGH SUNDAY/...DRY AND COLDER WX SHOULD CONTINUE FOR MUCH OF THE PERIOD...WITH WINDS GRADUALLY DIMINISHING. MAX TEMPS ON SAT SHOULD BE A COUPLE OF DEGREES WARMER THAN THOSE OF FRI AS H8-10 THICKNESSES AND H9 TEMPS SHOW A SLIGHT INCREASE...BUT MORE IDEAL RADIATIONAL COOLING CONDITIONS SAT NIGHT VIA LIGHT WINDS AND ONLY SCATTERED TO BROKEN HIGH CLOUDS AND RELATIVELY FRESH SNOW COVER OVER SOUTHERN CT AD FAR EASTERN LONG ISLAND SHOULD ALLOW TEMPS SAT NIGHT TO BE A LITTLE COLDER THAN THOSE OF FRI NIGHT OVER THE INTERIOR...WITH SOME SINGLE DIGITS POSSIBLE IN SOME SHELTERED INTERIOR VALLEYS. CLOUDS SHOULD INCREASE SUNDAY AS LOW PRESSURE ORGANIZING IN THE LEE OF THE ROCKIES ON SAT MOVES EAST ACROSS THE PLAINS STATES AND MID MISSISSIPPI VALLEY SUN AND SUN NIGHT. 00Z MODELS HOLD OFF ON ANY PRECIP UNTIL SUN NIGHT...BUT DUE TO UNCERTAINTIES IN TIMING THIS FAR OUT HAVE ELECTED TO KEEP CHANCE POP IN THE FORECAST FOR AT LEAST THE WESTERN HALF OF THE CWA FOR SUN AFTERNOON. TEMPS WILL BE IN THE MID AND UPPER 30S BUT COULD COOL OFF ENOUGH WITH ONSET OF PRECIP TO MAKE P-TYPE QUESTIONABLE...SO HAVE FORECAST RAIN OR SNOW. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...00Z GFS/NAM HAVE BOTH TRENDED COLDER WITH LOW PRESSURE SYSTEM FORECAST TO AFFECT THE AREA SUN NIGHT AND MON. THIS PRIMARY LOW SHOULD STALL OUT OVER THE GREAT LAKES REGION AS A REX BLOCK DEVELOPS OVER THE GREAT LAKES AND ONTARIO...WITH ANOTHER REX BLOCK IN PLACE OVER GREENLAND AND THE NORTH ATLANTIC. MEANWHILE A SECONDARY LOW DEVELOPS ALONG THE MID ATLANTIC COAST SUN NIGHT AND PASSES JUST S OF THE 40/70 BENCHMARK ON MON. PARTIAL THICKNESSES...H8 TEMPS AND RAW MODEL SOUNDINGS SUPPORT A COLDER SOLUTION WITH SNOW THROUGHOUT THE AREA...BUT THERE ARE SOME FLIES IN THE OINTMENT SUGGESTING MIXED PRECIP MAINLY ALONG AND SOUTH OF I-95...NAMELY ONSHORE LOW LEVEL FLOW...WEAK HIGH PRESSURE OVER NEW ENGLAND WITH ITS SUPPORTING MID LEVEL CONFLUENCE TOO FAR EAST TO BE IN AN IDEAL POSITION FOR AN ALL SNOW EVENT...AND WSW MID LEVEL FLOW WHICH COULD EASILY BRING IN WARMER AIR ALOFT IF THE PRIMARY LOW AND RESULTANT WAA ARE STRONGER THAN FORECAST. AS A RESULT HAVE NOT TINKERED WITH LONG TERM FORECAST ATTM EXCEPT TO MAKE P-TYPE FOR SUN NIGHT AND MON MORE CONSISTENT WITH FORECAST TEMPS....WITH A WINTRY MIX SUN EVENING CHANGING TO ALL SNOW LATER SUN NIGHT...THEN CHANGING BACK TO A WINTRY MIX ON MON. && .HYDROLOGY...DRY WX IS EXPECTED FOR THIS AFTERNOON THRU A GOOD PORTION OF SUNDAY. SO STAGES SHOULD HOLD STEADY THROUGH THE WEEKEND. && .AVIATION... CLOUD DECKS HAVE BEEN LOWERING AS SHORTWAVE MOVES EAST...BUT NOW DOWNSLOPE FLOW BREAKING UP THESE CLOUDS AND EXPECT SCT TO BKN VFR STRATO-CU THIS AFTERNOON. WINDS FROM THE NORTHWEST AROUND 330 DEGREES...AND THIS SHOULD HOLD FOR THE MOST PART. ACARS SOUNDINGS DO INDICATE ABOUT 30 KTS FOR POSSIBLE GUSTS THIS AFTERNOON. EXPECT WINDS TO REMAIN GUSTY AT ALL TERMINALS THROUGH 21Z...THEN FOR GUSTS TO DIMINISH OVER INLAND TERMINALS N/W OF NYC (TEB/SWF). ELSEWHERE EXPECT WINDS 15-20G25-30 THROUGH AT LEAST 12Z SAT WITH TEB/SWF HAVING GUSTS RESUMING AT AROUND 12Z SAT. EXPECT WIND DIRECTION OVER THE NEXT 24 HOURS TO BE OUT OF THE NW. && .MARINE...WINDS FINALLY INCREASING...A BIT SLOWER THAN EXPECTED...AND GALE WINDS ARE ANTICIPATED THIS AFTERNOON AND TONIGHT FOR THE OCEAN WATERS. AN OCCASIONAL GUST TO 35 KT POSSIBLE ELSEWHERE...BUT OVERALL SHOULD REMAIN BELOW GALE CONDITIONS ACROSS LI SOUND AND NY HARBOR. PRESSURE GRADIENT REMAINS TIGHT ACROSS THE AREA TONIGHT WITH MODEL SOUNDINGS DEPICTING A DEEP MIXED LAYER. WINDS WILL SUBSIDE BELOW GALE LEVELS ON SATURDAY...BUT SCA CONDITIONS WILL CONTINUE THROUGH THE DAY. NO SCA HEADLINE FOR THE OCEAN YET WITH THE INITIAL GALE WARNING ALREADY POSTED. WRN SOUND AND HARBOR MAY DROP BELOW SCA DURING THE AFTERNOON...BUT FOR SIMPLICITY KEPT THE SOUND/HARBOR ZONES WITH SCA THROUGHOUT THE DAY FOR NOW. WINDS WILL DROP BELOW SCA LEVELS EVERYWHERE SAT NIGHT AND REMAIN LIGHT ON SUN AS THE SFC HIGH PRESSURE RIDGE AXIS CROSSES THE REGION. FLOW THEN COMES AROUND TO NE AND INCREASES SUN NIGHT AND MON AS A LOW PRESSURE SYSTEM DEVELOPS ALONG THE MID ATLANTIC COAST AND MOVES OFFSHORE ON MON. SCA CONDITIONS APPEAR TO BE A GOOD BET AT THAT TIME AT LEAST ON THE OCEAN. SEAS NOW BUILDING TO 5-7 FT ON THE OCEAN AND ARE ABOUT 2 FT ON THE SOUND. COMBINATION OF STRONG WINDS...ROUGH SEAS AND COLD AIR TEMPERATURES WILL PRODUCE SOME LIGHT FREEZING SPRAY ON THE OCEAN WATERS TONIGHT. && OKX WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. NJ...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST SATURDAY FOR ANZ330-335- 338. GALE WARNING UNTIL 6 AM EST SATURDAY FOR ANZ350-353-355. && $$ NEAR TERM/MARINE/AVIATION/HYDROLOGY UPDATES...PW
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
855 PM CST SAT FEB 24 2007 .UPDATE... 855 PM CST UPDATED THE GRIDS AND ZONES TO ACCOUNT FOR NEW LAYOUT TO WINTER STORM WARNING VS. ICE STORM WARNING. BURST OF HVY SNOW WITH RATES OF 1 TO 2 INCHES PER HR OCCURRING WITH BAND NOW MOVING ACROSS FAR N AND NW SUBURBS OF CHICAGO. MIXED BAG OF LIGHTER SN AND FREEZING RAIN BEHIND THIS...THOUGH PRECIP IS MAINLY FREEZING RAIN OVR NW INDY. TEMPS WARM AS DEEP LOW NOW NR KANSAS CITY PUMPS WARM MOIST AIR NWD INTO NRN IL/NW INDY. PRECIP SHOULD TRANSITION FROM A MIX WHICH IS PREDOMINANTLY SNOW NOW...TO MORE OF A SLEET AND FREEZING RAIN SITUATION BY EARLY MORNING AS ELEVATED WARM LAYER AROUND H9 SURGES TO 2-3C ABV FREEZING. HANDEL && .DISCUSSION AFTERNOON FORECAST STRONG RAPIDLY OCCLUDING LOW OVER CENTRAL KANSAS DESTINED TO MOVE TOWARD NRN ILL LATER SUN AND MON BUT BE FILLING OVER TIME. INITIAL CONCERN HOWEVER IS APPROACHING BAND OF RAIN THROUGH CENTRAL ILL. SFC TEMPS ACROSS FCST AREA HAVE INCHED TOWARD 30-32F TODAY BUT HAVE STRONG CONCERNS ABOUT CONTINUING FEED OF DRY AIR FROM EAST. ONCE PRECIP FALLS INTO THIS ZONE THE WET BULB TEMP WILL BE REACHED WHICH IS WELL BELOW 32F. THUS ANY PROGRESS IN WARMING TODAY WILL BE OFFSET BY EVAP COOLING MUCH LESS DARKNESS. FOCUS OF APPROACHING PRECIP AREA APPEARS TO BE SINKING TOWARD THE OHIO VALLEY BUT MODELS SUGGEST VERY STRONG WARMING ALOFT WITH MARKED VEERING SIGNATURE IN MODEL AND ACARS WIND FIELDS. THIS SHOULD FORCE A PERIOD OF STEADY POTENTIALLY MODERATE RAIN FOR A FEW HOURS THIS EVENING BEFORE AREA IS OVER RUN BY A DEVELOPING DRY SLOT /ALOFT/ FROM SW. TIMIMG STILL ON TRACK FOR MAIN EVENT BETWEEN 00Z AND 06Z THIS EVENING. SOME MIX OF PRECIP IS LKLY MAINLY SLEET OVER SRN AND CENTRAL FCST AREA WITH SNOW AND SLEET FURTHER N ALONG THE WISCONSIN BORDER. ANY SNOW AMOUNTS WILL BE HELD DOWN BY PRECIP MIX. WITH LOW TRACKING OVERHEAD LATER SUN AND MON AIRMASS WITH COOL AND LINGERING PRECIP WILL BE TURNED TO SNOW. CANT RULE OUT AREAS OF LIGHT SNOW ACCUMULATION MAINLY SUNDAY NIGHT AND MONDAY AS UNDERMINED IMPULSES PIVOT AROUND DECAYING SYSTEM. IT WILL BE MID WEEK BEFORE SUSTAINED CLEARING OCCURS. UPPER AIR PATTERN SHOWS THE APPROACHING LOW RUNNING HEAD LONG INTO A TEMPORARY BLOCKING PATTERN WHICH ACCOUNTS FOR THE SLUGGISH RETREAT. HOWEVER THIS SITUATION WONT LAST LONG AND ANOTHER SIMILAR HIGH AMPLITUDE TROUGH FCST TO SWING THROUGH THE AREA ABOUT THUR-FRI. THIS TIME NO ICE. NEXT 12HRS WILL BE CRITICAL FOR FORECAST AREA. GIVEN EXPECTATION OF SUBFREEZING SFC TEMPS THROUGH AT LEAST THE FIST PART OF THE NIGHT AND POTENTIAL INTENSITY OF RAIN THE COURSE OF LEAST REGRET DICTATES AN ICE STORM WARNING FOR THE CENTRAL 2/3 OF FCST AREA WITH A WINTER STORM WARNING ALONG THE WISC BORDER...MAINLY FOR SNOW AND SLEET SOME FRZG RAIN. SOUTHERN THIRD OF AREA WILL CONTINUE A FREEZING RAIN ADVISORY. ALL ARE 6PM THIS EVENING TO 6AM SUNDAY. EXPECT MOST INTENSE PRECIPITATION DURING FIRST 6HRS THIS EVENING. DRYING ALOFT LATER IN THE NIGHT MAY REDUCE PRECIP TO DRIZZLE. THRESHOLD FOR ICE STORM IS QUARTER INCH OF ICE AND WITH EXPECTED INTENSITY OF RAIN THIS LEVEL MAY BE REACHED IN MANY SPOTS. TEMPS COULD STRUGGLE ABOVE FREEZING LATER TONIGHT IN WARNING AREA...AND LIKELY BE IN LOW TO MID 30S ON BY SUNDAY AFTERNOON. THIS IS ONE OF THE MORE CHALLENGING FCST SITUATIONS OF RECENT MEMORY. KML && .AVIATION... 610 PM CST MAJOR WINTER STORM SYSTEM MOVING NE FROM THE CNTRL PLAINS INTO NRN IL BY AFTN SUNDAY. PLENTY OF GULF MSTR MOVING THIS WAY AND OVERRUNNING WARM FNT. RAIN FALLING FROM WARM LAYER TO ENTRENCHED FRZN LAYER RESULTING IN FREEZING RAIN AND SLEET WITH SNOW MORE PROMINANT IN RFD AND ORD. AS WARM LAYER INTRUDES OVERHEAD RFD AND ORD...SNOW CUD MIX OR CHANGE TEMPORARILY TO SLEET OR FRZG RAIN OVERNIGHT. DAYTIME WARMING SUNDAY AT SFC MAY ALLOW JUST RAINFALL IF WARM LAYER REMAINS INTACT OVERHEAD. HOWEVER DURING AFTN...COLD WRAPARND TEMPS UNDERCUTTING AND WEAKENING UPR LOW AND PROBLY RETURNING OR BECOMING ALL SNOW BY END OF DAY. IFR CIGS AND VSBY WILL BE FREQUENTLY IN THE TEMPO GROUP IF NOT PREDOMINANT NEXT 24 HRS. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH ACROSS AREA. IF EVER A DAY TO THINK HARD ABOUT NOT FLYING...THIS IS IT. RLB && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WARNING NORTH AND WEST OF COOK-LASALLE CNTY LINE THROUGH NOON SUN ICE STORM WARNING IROQUOIS-FORD-LIVINGSTON-KANKAKEE TIL 6AM SUN .IN...ICE STORM WARNING TIL 6AM CST /7AM EST/ SUN. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
610 PM CST SAT FEB 24 2007 .DISCUSSION AFTERNOON FORECAST STRONG RAPIDLY OCCLUDING LOW OVER CENTRAL KANSAS DESTINED TO MOVE TOWARD NRN ILL LATER SUN AND MON BUT BE FILLING OVER TIME. INITIAL CONCERN HOWEVER IS APPROACHING BAND OF RAIN THROUGH CENTRAL ILL. SFC TEMPS ACROSS FCST AREA HAVE INCHED TOWARD 30-32F TODAY BUT HAVE STRONG CONCERNS ABOUT CONTINUING FEED OF DRY AIR FROM EAST. ONCE PRECIP FALLS INTO THIS ZONE THE WET BULB TEMP WILL BE REACHED WHICH IS WELL BELOW 32F. THUS ANY PROGRESS IN WARMING TODAY WILL BE OFFSET BY EVAP COOLING MUCH LESS DARKNESS. FOCUS OF APPROACHING PRECIP AREA APPEARS TO BE SINKING TOWARD THE OHIO VALLEY BUT MODELS SUGGEST VERY STRONG WARMING ALOFT WITH MARKED VEERING SIGNATURE IN MODEL AND ACARS WIND FIELDS. THIS SHOULD FORCE A PERIOD OF STEADY POTENTIALLY MODERATE RAIN FOR A FEW HOURS THIS EVENING BEFORE AREA IS OVER RUN BY A DEVELOPING DRY SLOT /ALOFT/ FROM SW. TIMIMG STILL ON TRACK FOR MAIN EVENT BETWEEN 00Z AND 06Z THIS EVENING. SOME MIX OF PRECIP IS LKLY MAINLY SLEET OVER SRN AND CENTRAL FCST AREA WITH SNOW AND SLEET FURTHER N ALONG THE WISCONSIN BORDER. ANY SNOW AMOUNTS WILL BE HELD DOWN BY PRECIP MIX. WITH LOW TRACKING OVERHEAD LATER SUN AND MON AIRMASS WITH COOL AND LINGERING PRECIP WILL BE TURNED TO SNOW. CANT RULE OUT AREAS OF LIGHT SNOW ACCUMULATION MAINLY SUNDAY NIGHT AND MONDAY AS UNDERMINED IMPULSES PIVOT AROUND DECAYING SYSTEM. IT WILL BE MID WEEK BEFORE SUSTAINED CLEARING OCCURS. UPPER AIR PATTERN SHOWS THE APPROACHING LOW RUNNING HEAD LONG INTO A TEMPORARY BLOCKING PATTERN WHICH ACCOUNTS FOR THE SLUGGISH RETREAT. HOWEVER THIS SITUATION WONT LAST LONG AND ANOTHER SIMILAR HIGH AMPLITUDE TROUGH FCST TO SWING THROUGH THE AREA ABOUT THUR-FRI. THIS TIME NO ICE. NEXT 12HRS WILL BE CRITICAL FOR FORECAST AREA. GIVEN EXPECTATION OF SUBFREEZING SFC TEMPS THROUGH AT LEAST THE FIST PART OF THE NIGHT AND POTENTIAL INTENSITY OF RAIN THE COURSE OF LEAST REGRET DICTATES AN ICE STORM WARNING FOR THE CENTRAL 2/3 OF FCST AREA WITH A WINTER STORM WARNING ALONG THE WISC BORDER...MAINLY FOR SNOW AND SLEET SOME FRZG RAIN. SOUTHERN THIRD OF AREA WILL CONTINUE A FREEZING RAIN ADVISORY. ALL ARE 6PM THIS EVENING TO 6AM SUNDAY. EXPECT MOST INTENSE PRECIPITATION DURING FIRST 6HRS THIS EVENING. DRYING ALOFT LATER IN THE NIGHT MAY REDUCE PRECIP TO DRIZZLE. THRESHOLD FOR ICE STORM IS QUARTER INCH OF ICE AND WITH EXPECTED INTENSITY OF RAIN THIS LEVEL MAY BE REACHED IN MANY SPOTS. TEMPS COULD STRUGGLE ABOVE FREEZING LATER TONIGHT IN WARNING AREA...AND LIKELY BE IN LOW TO MID 30S ON BY SUNDAY AFTERNOON. THIS IS ONE OF THE MORE CHALLENGING FCST SITUATIONS OF RECENT MEMORY. KML && .AVIATION... 610 PM CST MAJOR WINTER STORM SYSTEM MOVING NE FROM THE CNTRL PLAINS INTO NRN IL BY AFTN SUNDAY. PLENTY OF GULF MSTR MOVING THIS WAY AND OVERRUNNING WARM FNT. RAIN FALLING FROM WARM LAYER TO ENTRENCHED FRZN LAYER RESULTING IN FREEZING RAIN AND SLEET WITH SNOW MORE PROMINANT IN RFD AND ORD. AS WARM LAYER INTRUDES OVERHEAD RFD AND ORD...SNOW CUD MIX OR CHANGE TEMPORARILY TO SLEET OR FRZG RAIN OVERNIGHT. DAYTIME WARMING SUNDAY AT SFC MAY ALLOW JUST RAINFALL IF WARM LAYER REMAINS INTACT OVERHEAD. HOWEVER DURING AFTN...COLD WRAPARND TEMPS UNDERCUTTING AND WEAKENING UPR LOW AND PROBLY RETURNING OR BECOMING ALL SNOW BY END OF DAY. IFR CIGS AND VSBY WILL BE FREQUENTLY IN THE TEMPO GROUP IF NOT PREDOMINANT NEXT 24 HRS. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH ACROSS AREA. IF EVER A DAY TO THINK HARD ABOUT NOT FLYING...THIS IS IT. RLB && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WARNING 6PM SAT TO 6AM SUN FOR WISC BORDER COUNTIES ICE STORM WARNING THRU 6AM OGLE TO COOK COUNTY ON SOUTH. .IN...ICE STORM WARNING LAKE PORTER NEWTON AND JASPER AND BENTON THRU 6AM SUN. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
230 PM CST FRI FEB 23 2007 .DISCUSSION...AFTERNOON FORECAST... INITIAL ROUND OF MID LEVEL WARM ADVECTION SENDING A PLUME OF CLOUDS ACROSS FCST ARE THIS AFTERNOON. ASIDE FROM PUTTING A LID ON TEMPERATURE RISE LOW LEVEL DRYNESS HAS PRECLUDED ANY SFC PRECIP. UPPER TROUGH AND SURFACE FRONT MOVING INTO WRN COLO THIS AFTERNOON AND WARM INCRESINGLY MOIST AIRMASS ADVECTING N INTO CENTRAL PLAINS. SFC LO EXPECTED TO FORM OVER THE WESTERN HIGH PLAINS OF COLO-KANSAS TONIGHT AND TRACK NE TOWARD MID MISS VALLEY SAT INTO EARLY SUNDAY. MODELS SUGGEST THIS SYSTEM WILL RAPIDLY OCCLUDE AND ACTURALLY BEGIN DECAY/FILLING PROCESS AS IT REACHS LOWER WESTERN LAKES SUNDAY. LOW LEVELS AS SAMPLED BY TAMDAR FLIGHTS IN CENTRAL IL ARE VERY DRY AND SE WINDS CONTINUE TO ADVECT TEENS DEW PTS INTO REGION THIS AFTERNOON. NEW GFS HAS COME INTO PHASE WITH NAM AND OTHER MODELS IN SLOWING ONSET OF APPROAHING LOW AND PRECI UNTIL LATER SAT. THE UPSHOT OF ALL THIS IS AN EXPECTED BEGINNING OF PRECIP SAT AFTN OVER NWRN IL SPREADING INTO NW IN AFTER SUNSET. LOW DEW POINT AIR AND DRY LOWER LEVELS INDICATE AN INITIAL LOW WET BULB /BELOW FREEZING/ CONDITION TO BEGIN ANY PRECIP AS SNOW. WIND FIELD AROUND APPROACHING LOW WILL INCR RAPIDLY LATER SAT AND SAT NIGHT WITH VERY WELL DEVELOPED WARM ADVECTION SIGNAL SEEN IN MODEL SOUNDINGS AFTER 00Z SUN /6PM SAT/. THIS SIGNAL IS IN VICINITY OF THE TROWAL FEATURE OF THE OCCLUSION AND PRONE TO THE MOST INTENSE PRECIP. MODEL SOUNDINGS ALSO REVEAL THE TEMPERATURE PROFILE TO HOVER AROUND 0 DEG C BELOW 850MB OVER AT LEAST THE NRN HALF OF THE FCST AREA INTO SUNDAY MORNING WHICH SUPPORTS A MIXED PRECIP WITH THE POTENTIAL FOR SIGNIFICANT FRZG RAIN OR SLEET. SNOW MAY DOMINATE TOWARD THE WISC BORDER WITH GRID TOTAL OF 5-7 INCH STORM TOTAL REFLECTING THE INITIAL GUESS. ELSEWHERE ACCUMULATIONS OF SLEET AND SOME FREEZING RAIN WILL REDUCE TOTALS. RAIN WILL LIKELY DOMINATE SOUTH OF THE KANKAKEE RIVER TOWARD PONTIAC. MOST CONCENTRATED PRECIP PERIOD APPEARS TO BE BETWEEN 6PM SAT AND 6AM SUN WITH RESIDUAL SNOW CONTINUING SUNDAY. AS UPPER TROUGH WEAKENS OVERHEAD AND SLOWLY RECEDES TO THE EAST PERIODS OF LIGHT SNOW ARE EXPECTED TO PERSIST INTO MON AND TUE. ANOTHER HIGH AMPLITUDE UPPER TROUGH MOVING ONTO THE WEST COAST AT MIDWEEK WILL KICK OFF ANOTHER PLAINS CYCLONE ABOUT THURS WITH A MODEST WARM UP TOWARD THE END OF THE WEEK. TEMPS TONIGHT WILL BE MODIFIED BY CLOUDS ALTHOUGH IF CLOUDS THIN LATER IN THE NIGHT DRY AIR MAY ALLOW BRIEF DIP..BUT WILL GO ABOVE GUIDANCE PLAYING FOR CLOUDS. THIS SYSTEM HAS THE POTENTIAL TO BE A SIGNIFICANT PRECIPITATION PRODUCER GIVEN THE SLOWING NATURE OF MOVEMENT AS IT APPROACHES. PRECIP TYPE UNCERTAINTY IS A CONCERN ALTHOUGH THAT MAY BE OFFSET SOME BY THE SE TRAJECTORY OF THE INCOMING AIRMASS..AS OPPOSED TO A NE COMPONENT. SNOW TOTALS GOING NORTH TOWARD THE WISC BORDER WILL INCREASE RAPIDLY ESPECIALLY NORTH OF THE BORDER. WHILE THE OVERALL SCENARIO HAS BECOME MORE CLEAR THE DETAILS OF PRECIP TYPE IS A LINGERING CONCERN KML && .AVIATION... 18Z TAFS...NEXT 24HRS WILL BE RELATIVELY QUIET WITH PRECIP TO BEGIN SATURDAY AFTERNOON...AFTER THE END OF THIS PERIOD. WINDS TURNED MORE EASTERLY THIS MORNING PUSHING STRATOCU DECK OVER THE LAKE ONSHORE. EXPECT PREVAILING SCT 2-3KFT CLOUDS THRU THE AFTERNOON...PERHAPS BKN FOR AN HR OR TWO TO START BUT TREND SHOULD BE TO SCATTER OUT AND DISSIPATE BY EVENING. OTHERWISE BKN/OVC MID LEVEL DECK WILL SLOWLY LOWER THRU THE PERIOD. COULD BE A FEW SPRINKLES TODAY OR FLURRIES TONIGHT FROM THIS MID DECK...BUT EXPECT ANYTHING THAT DOES FALL TO BE VIRGA AS LOW LEVELS ARE VERY DRY. EASTERLY WINDS CONTINUE 10-15KTS THRU EVENING AND BEGIN TO INCREASE TONIGHT WITH GUSTS TO 20KTS OVERNIGHT. GUSTS CONTINUE TO INCREASE TO 25KTS THRU SAT MORNING...PERHAPS A FEW HIGHER AS WINDS TURN ESE. DEEP LOW PRESSURE APPROACHES THE AREA SATURDAY AND SATURDAY NIGHT... SPREADING PRECIP ACROSS THE AREA SATURDAY AFTERNOON/EVENING. PRECIP TYPE WITH THIS FORECAST IS GOING TO BE DIFFICULT AS MODEL SOUNDINGS AND THERMAL PROFILES SUGGEST A PROLONGED PERIOD OF MIXED PRECIP WITH CIGS QUICKLY LOWERING INTO IFR SAT EVENING. ESE WINDS ALSO CONTINUE TO INCREASE WITH GUSTS AS HIGH AS 30-35KTS SAT EVENING. CMS && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WATCH 18Z SATURDAY TO 00Z MONDAY WINNEBAGO BOONE MCHENRY LAKE COOK DUPAGE KANE DEKALB OGLE LEE LASALLE KENDALL GRUNDY WILL. .IN...WINTER STORM WATCH 18Z SATURDAY TO 00Z MONDAY LAKE PORTER. .LM...GALE WRNG ALL LM AND NR SHORES 21Z SAT TO 21Z SUN.. && $$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
844 PM EST SAT FEB 24 2007 ...DESTRUCTIVE ICE STORM TONIGHT... .UPDATE... TREMENDOUS ICE STORM IN PROGRESS ACRS SRN CWA ATTM W/REPORTS OF HEAVY ICING ALREADY W/SOME POWER OUTAGES FM VALPO TO MONTICELLO TO PERU. DEEP LAYERED CYCLONE OVR NE KS WILL SLOWLY EDGE EWD OVERNIGHT AND BACK LL FLW FURTHER. DEEP LOW/MID LVL MSTR PLUME ACRS IL/SW IN WILL SHIFT EWD AND AIDE NEWD EXPANSION OF FZRA AND SLEET INITIALLY AND THEN GIVING WAY TO MAINLY FZRA AFT 05Z SW HALF PER 00Z RUC AND RECENT TAMDAR SOUNDING OUT OF KFWA. EXCEPTION MAY BE FAR NE WHERE DEEPEST LL COLD AIR RESIDES AND EXPECT SNOW SLEET MIX THERE CHANGING TO MAINLY FZRA LATE. SFC OBS/RADAR INDICATE FM .1-.2 INCH PER HOUR ICE ACCRETION RATES WILL CONT THROUGH 09Z. TOP END ICE ACCUMULATIONS MAY END UP HIGHER THEN GOING 3/4 MENTION IN WSW/ZFP BUT CLOSE. SRN CWA WILL CONT TO SLOWLY WARM TO ABV FREEZING AS SFC WINDS BACK W/MID 30S NOTED NOW ACRS CNTRL INDIANA. WILL WAIT FOR THAT TO HAPPEN BFR MAKING ANY DECISION ON SCALING BACK GOING WARNINGS. WILL CONT TO MONITOR BUT SO FAR FCST PLAYING OUT AS XPCD W/NO EARLY UPDATES PLANNED AT THIS TIME. && .AVIATION... VFR CONDS EARLY ON WILL VERY QUICKLY DETERIORATE IN FACE OF INTENSIFYING LL MSTR FLUX AND TOP DOWN SATURATION W/WIDESPREAD IFR CONDS XPCD TWD 06Z AS MOD/HEAVY FZRA/PL OVERSPREADS THE TERMINALS. 21Z RUC LOOKS TO THE BEST HANDLE SHORT TERM ALTHOUGH NOT CAPTURING NEWD EXTENT OF LEADING EDGE OF FZRA/PL. HWVR DEFINITELY PREFER ITS SFC/BNDRY LYR DEPICTION W/SIG DIABATIC COOLING ADJUSTMENT EARLY ON GIVEN LOW THETA-E WEDGE IN PLACE AND SIG ADIABATIC COOLING LTR ON IN ADV OF MID LVL SW TROUGH AND STG VERTICAL MOTION. CURRENT HEADLINES WELL AND GOOD WITH ICE ACCUMULATIONS OVER 1/4 INCH ALREADY ACRS WHITE COUNTY. FURTHER UPSTREAM...FZRA FALLING AT THE RATE OF 1/4+ INCH AN HOUR ACRS KIND CWA. RUC WOULD SUGGEST SRN CWA WILL SWITCH OVER TO RAIN TWD 09Z. && .SHORT TERM... SHORT/DELAYED DISCUSSION DUE TO MULTIPLE ISSUES. SLEET AND FREEZING RAIN HAS BEEN SLOWLY OVERSPREADING ILLINOIS MUCH OF THE DAY. SOME LOCATIONS IN WESTERN ILLINOIS HAVE ALREADY REPORTED UPWARDS OF A HALF INCH OF ICE. OVER THE PAST HOUR THE AREA OF PRECIP HAS ACCELERATED NE AND HAS REACHED WHITE COUNTY WITH A MIXTURE OF SLEET AND RAIN. WARMER SFC TEMPERATURES ALREADY POISED TO MOVE INTO FAR SOUTHWEST COUNTIES POSSIBLY BY THE OVERNIGHT HOURS. INCREASINGLY DIFFICULT FORECAST AS A RESULT...REQUIRING EXPANDING THE ICE STORM WARNING FURTHER NORTH TO ALONG AND SOUTH OF US 6. ICE ACCUMULATIONS OF ONE HALF TO THREE QUARTERS OF AN INCH OR MORE ARE EXPECTED...ESPECIALLY ACROSS THE NORTHERN HALF OF THE ICE STORM WARNING AREA. WHILE ACCUMULATIONS WILL BE HEAVY FURTHER SOUTH...TEMPS POSSIBLY CLIMBING ABOVE FREEZING WILL ALLOW A STOP TO THE ACCUMULATION OF ICE. EXACTLY WHEN THIS OCCURS REMAINS IN QUESTION...HENCE NO CHANGES TO THE WARNING. FURTHER NORTH...MIXTURE OF SNOW...SLEET AND FREEZING RAIN WILL CAUSE LOTS OF PROBLEMS. ICE ACCUMS OF UP TO QUARTER INCH AS WELL AS SLEET UP TO ONE HALF INCH ARE EXPECTED TONIGHT. IF TREND CONTINUES ON WARMER AIR BEING DRAWN NORTH...THEN SIGNIFICANT ICING COULD ALSO OCCUR ACROSS THE WINTER STORM WARNING AREA. ON SUNDAY...GRIDS CHANGED TO REFLECT THE WARMER AIR ARRIVING WITH EITHER RAIN OR RAIN/SNOW EVENTUALLY DOMINATING SOUTHERN QUARTER TO HALF OF CWA. WILL LEAVE REST OF DETAILS TO LATER SHIFTS. && .LONG TERM... SUNDAY NIGHT THROUGH SATURDAY... FORECAST PERIOD BEGINS WITH STACKED SYSTEM OVER THE AREA. MODELS DIFFERING ON EXACT PLACEMENT WITH NAM FURTHER WEST BACK OVER IOWA AND ILLINOIS SUNDAY NIGHT AND GFS OVER SOUTHERN GREAT LAKES. MODEL SOUNDINGS INDICATING SE CWA MAY SEE BRIEF PERIOD OF LIQUID PRECIP IN THE EVENING BEFORE CHANGING TO SNOW OTHERWISE GOING FORECAST OF SNOW REST OF CWA LOOKS GOOD. STACKED SYSTEM REMAINS OVER THE AREA MONDAY...NOT LOOKING FOR MUCH DIURNAL CHANGE IN TEMPS SO WILL KEEP HIGHS NEAR FREEZING OVER CWA...COLUMN SATURATED THROUGH 700MB AND SUFFICIENTLY COLD TO SUPPORT ICE PRODUCTION AT CLOUD LEVEL SO SHOULD BE ALL SNOW EVEN IF SOME LOCATIONS MANAGE TO NUDGE ABOVE FREEZING. SYSTEM EVENTUALLY KICKS EAST ALLOWING FOR UPSTREAM RIDGING TO WORK INTO THE AREA GIVING DRY FCST TUE NITE AND WEDNESDAY. NEXT SYSTEM THEN DIGS INTO THE PLAINS BRINGING ANOTHER CHANCE FOR PRECIP THURSDAY AND FRIDAY. WILL STAY WITH CURRENT GRIDS RA/SN MIX DURING THE AFTERNOON AND SN NITE/MORNING HOURS. EXPECT TEMPS 5-10 BELOW NORMAL TUE THEN NEAR NORMAL REMAINDER OF EXTENDED....WITH BEST CHANCE OF ABOVE NORMAL TEMPS ON THU IN ADVANCE OF NEXT SYSTEM. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...ICE STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR INZ008-009-018-026-027-033-034. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR INZ006-007. WINTER STORM WARNING UNTIL 12 PM EST /11 AM CST/ SUNDAY FOR INZ003>005. ICE STORM WARNING UNTIL 12 PM EST /11 AM CST/ SUNDAY FOR INZ012>017-020-022>025-032. MI...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR MIZ079>081. WINTER STORM WARNING UNTIL 12 PM EST SUNDAY FOR MIZ077-078. OH...ICE STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR OHZ004-005-015-016-024-025. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR OHZ001-002. LM...BRISK WIND ADVISORY UNTIL 5 PM EST SUNDAY FOR LMZ043-046. && $$ AVIATION/UPDATE...HOLSTEN SHORT TERM/...FISHER LONG TERM...LOGSDON
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
1008 PM EST SAT FEB 24 2007 .UPDATE... MAIN FCST ISSUE OVERNIGHT IS TIMING ONSET OF SNOW ACROSS THE SRN FCST AREA AS MOISTURE SURGE FROM THE S FIGHTS VERY DRY AIRMASS OVER UPPER MI. WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A DEEP/STRONG MIDLEVEL SYSTEM CENTERED OVER ERN KS. 00Z RAOBS REVEAL THE INTENSITY OF SYSTEM AS EXTREMELY IMPRESSIVE 12HR 500MB HEIGHT FALLS OF 250M HAVE OCCURRED OVER SW MO. TO E...SYSTEM HAS FORCED THE DEVELOPMENT OF EQUALLY IMPRESSIVE LOW-LEVEL JET UPWARDS OF 60-80KT AT 850MB ACROSS THE MID MISSISSIPPI VALLEY PER 00Z RAOBS/PROFILERS. TREMENDOUS MOISTURE ADVECTION COMBINED WITH STRONG DYNAMICS IS RESULTING IN A MASSIVE OF AREA OF PCPN FROM THE LWR OHIO VALLEY TO THE UPPER MISSISSIPPI VALLEY. 00Z RAOBS INDICATE PRECIPITABLE WATER OF 200-275PCT OF NORMAL FROM MN TO THE GULF COAST...SUPPORTING THE POTENTIAL FOR HVY PCPN FROM THIS SYSTEM. CLOSER TO HOME...IT WILL BE A BATTLE BTWN THE INCOMING MOISTURE SURGE AND THE DRY AIRMASS RESIDING OVER UPPER MI WHICH CONTINUES TO BE HELD IN PLACE BY DRY ERLY LOW-LEVEL FLOW. 00Z KAPX SOUNDING SHOWED VERY DRY AIR BTWN 700MB AND 850MB (DWPT DEPRESSIONS WERE 30-40C). THIS IS REPRESENTATIVE OF THE LOW-LEVEL DRY AIRMASS THAT CONTINUES TO ADVECT WNW INTO UPPER MI. EVENING TAMDAR SOUNDING FROM KSAW SHOWS A SIMILAR DRY LAYER...BUT IT IS NOT AS DEEP...BEING CONFINED TO THE 900-800MB LAYER. IT IS ALWAYS A VERY DIFFICULT FCST ISSUE TO DETERMINE WHEN A DRY LAYER WILL BE SATURATED...BUT DON`T THINK THE DRY AIR TONIGHT WILL BE ABLE TO HOLD OFF THE STRONG ISENTROPIC ASCENT/DEEP LAYER FORCING THAT IS SUPPORTING THE MDT/HVY PCPN SHIELD MOVING N INTO WI ATTM. AT THIS POINT...WILL MAKE SOME MINOR ADJUSTMENTS TO DELAY HIGHER POPS OVERNIGHT ACROSS THE S....BUT FULLY EXPECT SNOW TO DEVELOP NEAR THE WI BORDER NO LATER THAN BTWN 09-12Z. DESPITE THE INITIAL DRY AIR...HAVE SOME CONCERN THAT HEADLINES MAY NEED TO BE EXPANDED AS 18Z GFS WAS A BIT MORE AGGRESSIVE BRINGING SNOW N INTO MORE OF UPPER MI. 18Z RUN OF THE LOCAL NAMERICAN WRF-ARW IS VERY AGGRESSIVE WITH NWD PUSH OF SNOW SUN...SUGGESTING HEADLINES WILL NEED TO BE EXPANDED TO INCLUDE NEARLY ALL OF THE FCST AREA. IT SHOWS PCPN AMOUNTS OF 0.5 TO 0.75 INCHES ACROSS ALL BUT THE NW AND FAR E BY 06Z SUN. QUICK CHECK OF INCOMING 00Z NAM SHOWS THAT IT IS HOLDING THE LINE...ALLOWING DRY AIR TO PREVAIL TO THE N. IT STRONGLY SUPPORTS GOING HEADLINE AREAS WITH NO NEED TO EXPAND. SO...NO CHANGES ARE NEEDED TO SUN FCST RIGHT NOW. MENOMINEE COUNTY WILL BE HIT HARDEST BY THIS WINTER STORM. CONDITIONS WILL BE WORST IN EXPOSED AREAS ALONG THE BAY AS COASTAL CONVERGENCE WILL BOOST WINDS SPEEDS THERE...CREATING NEAR BLIZZARD CONDITIONS. && .PREV DISCUSSION (ISSUED AT 357 PM EST)... TAKING A LOOK AT CURRENT CONDITIONS...HIGH PRESSURE RULES...AT LEAST THE NORTHEASTERN TWO THIRDS OF THE REGION. THE CENTER OF HIGH PRESSURE IS WELL TO OUR NORTHEAST...WITH ITS CORE OVER HUDSON BAY. THIS HIGH WILL NOT BUDGE MUCH OVER THE NEXT SEVERAL DAYS...HELPING TO KEEP THE EXTREME EASTERN PORTIONS OF THE CWA CLOUD FREE...AND DRYING UP THE LOWER LEVELS OF THE ATMOSPHERE...SLOWING DOWN THE ONSET OF SNOW FROM THE SOUTHWEST. LOOKING TO OUR SOUTHWEST...A SLOWLY WEAKENING LOW OVER EASTERN KANSAS IS POISED TO HEAD INTO THE GREAT LAKES REGION...BRINGING ITS MIXED BAG OF PRECIPITATION TOWARDS THE AREA. FREEZING RAIN WAS BEING REPORTED AS FAR NORTH AS SOUTHEASTERN MINNESOTA AND WEST CENTRAL WISCONSIN...AS TEMPERATURES HOVER RIGHT AROUND THE FREEZING MARK. WITH PLENTY OF GULF MOISTURE TO WORK WITH...THUNDERSTORMS WERE COMMON FROM LOUISIANA UP THROUGH EASTERN MISSOURI...AND THEN BACK INTO KANSAS AROUND THE SURFACE LOW...OUT AHEAD OF THE 115KT 250MB JET ACROSS NORTHERN TEXAS AND WESTERN ARKANSAS. MAIN FCST CONCERNS ARE HANDLING OF POTENT SHRTWV SET TO LIFT NE FM THE SRN PLAINS AND SN TIMING/AMTS/HEADLINES. PER NCEP PREFERENCE... GENERALLY FOLLOWED THE GFS THRU F36...THEN A BLEND OF GFS/NAM AFT F36 FOR EVOLVING LO PRES SYS. FOR TNGT...125KT H3 JET MAX ROUNDING UPR LO OVER THE SRN ROCKIES FCST TO LIFT NEWD AND DRAG OCCLUDING LO TO THE MO/IA BORDER BY 12Z SUN...FARTHER N THAN FCST BY PREVIOUS GUIDANCE BUT NOT UNRSNBL CONSIDERING THE HEFTY DYNAMICS THAT CAUSED 00Z-12Z H3 HGT FALLS UP TO 200M AT AMA LAST NGT. NAM IS EVEN FARTHER N WITH THE CENTER OF LOWEST HGTS/PRES (INTO CNTRL IA)...BUT WL FOLLOW MORE CONSISTENT GFS FOR NOW. THE AREA OF UPR DVGC TO THE N OF THE UPR JET ROUNDING THE E SIDE OF THE LO FCST TO LIFT N INTO THE FA AFT MIDNGT. QUESTION REMAINS HOW QUICKLY/EFFECTIVELY ACCOMPANYING UVV CAN SATURATE THE BONE DRY LO-MID LVLS SHOWN ON THE 12Z APX RAOB/ 15Z TAMDAR SDNG FM TVC THAT IS REPRESENTATIVE OF AIRMASS OVER THE FA. GIVEN THE SHARP GRADIENT OF MSTR BTWN GRB/APX AT 12Z...EXPECT A VERY SHARP GRADIENT BTWN MODERATE SN AND LTL IF ANY SN. LLVL FLOW FCST TO REMAIN E TNGT...MAXIMIZING DRY ADVCTN. EXPECT A MAINLY DRY EVNG...BUT WL THEN INCRS POPS OVERNGT NEAR THE WI BORDER WITH ARRIVAL OF UPR DVGC. ADJUSTED FOR SLOWLY FALLING TO STEADY TEMPERATURES...MAINLY ACROSS THE WESTERN HALF OF THE CWA THROUGH MIDNIGHT TONIGHT...GIVEN GOOD MIXING IN THE LOWER LEVELS AND CLOUD COVER. AS FOR SUNDAY NIGHT...WENT SLIGHTLY COOLER WEST AND WARMER EAST FOR HIGH TEMPERATURES GIVEN THE FACT THAT CLOUDS WILL STILL HAVE A TOUGH TIME GETTING INTO THE EASTERN MOST COUNTIES OF THE CWA. NAM/GFS IN GOOD AGREEMENT SHOWING QPF BULLSEYE ARND 0.50 INCH S OF IMT-ESC TO MNM BTWN 12Z-18Z SUN UNDER AREA OF SHARPER H4-2 DVGC IN LEFT EXIT OF UPR JET LIFTING INTO THE LWR GRT LKS INTERACTS WITH SHARPER ISENTROPIC LIFT ON THE 280-300K SFC (H85-6)/ESE H85 WINDS TO 50KT/AXIS OF HIER SPECIFIC HUMIDITY (ABOUT 3 G/KG AT H7-75)/SHARPER H85-7 FGEN AND WHERE E LLVL FLOW OFFERS POTENTIAL FOR LK ENHANCEMENT OFF NRN LK MI. 280-290KISENTROPIC LIFT/MSTR TO THE NE IS QUITE A BIT WEAKER/ LESS...SO EXPECT A SHARP TRANSITION TO JUST THICKENING MID CLD ASSOCIATED WITH THE BETTER LIFT PRESENT THERE ON THE 300K SFC. THE BETTER ISENTROPIC LIFT/UPR DVGC/FGEN IS FCST TO DRIFT TO THE NE IN THE AFTN INTO THE DRIER AIR...SO THE HVY SN IN THE MRNG OVER THE SCNTRL MAY DIMINISH A BIT IN THE AFTN. TENDED TO SHARPEN THE NRN EDGE OF THE HIER QPF VS WHAT WAS FCST BY GUIDANCE TO ACCOUNT FOR TENACIOUS DRY AIR ASSOCIATED WITH SLOWLY BACKING LLVL FLOW AND MODEL TENDENCY TO SMOOTH QPF TOO FAR INTO THE DRIER AIR. ON SUN NGT/MON...GFS/NAM INDICATE OCCLUDED LO DRIFTING SLOWLY E... WITH FA IN GENERAL UPR DVGC TO THE N OF CLOSED LO CENTER. BEST H85-5 QVECTOR CNVGC REMAINS OVER THE SCNTRL ZNS. ALTHOUGH THERE IS A SLOW BACKING TREND TO THE LLVL WINDS...FLOW REMAINS FVRBL FOR A CONTINUED LONG FETCH ACRS NRN LK MI AND PERSISTENT WEAK LK ENHANCEMENT... MAINLY S OF HIGHWAY 2. BUT CONSIDERING THE LACK OF SHARP PERSISTENT FGEN AND APPRECIABLE JET DYNAMICS/SHARPER UPR DVGC...AND TENDENCY FOR SLOWLY BACKING LLVL FLOW TO ADVECT LLVL DRY AIR INTO THE FA AND WEAKEN THE OCCLUSION TO THE S...THINK SN INTENSITY WL BE LESS THAN EARLY ON SUN. BEST CHC FOR ADDITIONAL HEAVIER SN WL BE OVER THE FAR SCNTRL WHERE THERE IS POTENTIAL FOR LK ENHANCEMENT/UPSLOPING. SLOWED THE EXIT OF WEATHER DOWN SLIGHTLY...ADDING FLURRIES BEHIND THE DEPARTING SYSTEM...FOR TUESDAY...WITH THE EXITING 500MB LOW STILL STUCK NEAR CHICAGO AND NORTHERN INDIANA. UPGRADED GOING WATCH TO WRNG FOR DELTA/DICKINSON/MNM COUNTIES FOR SUN THRU MON EVEN THOUGH SN INTENSITY AT MOST PLACES WL TEND TO DIMINISH SUN NGT/MON. SINCE BEST DYNAMICS ON SUN WL MISS IRON COUNTY TO THE E AND THERE IS LESS CHC FOR APPRECIABLE LK ENHANCEMENT THERE...OPTED TO ISSUE ONLY ADVY FOR THAT COUNTY. IN THE MEDIUM/EXTENDED RANGE...EXPECT HI PRES RDG TO BRING RELATIVELY TRANQUIL WX TUE NGT THRU WED BEFORE LO PRES E OF DEEPENING TROF IN THE ROCKIES EJECTS TO THE NE. OPERATIONAL GUIDANCE HAS COME INTO BETTER AGREEMENT SHOWING LO TRACKING TO THE W OF THE CWA INTO MN BY LATE THU AND THEN INTO ONTARIO ON FRI WHILE DRAGGING AN OCCLUSION ACRS THE FA AS ANOTHER LO DVLPS IN THE OHIO VALLEY. EXPANDED AREA OF MIXED PCPN TO INCLUDE RA OVER THE SCNTRL ON THU/THU NGT CONSIDERING THE STRENGTH OF SLY FLOW AHEAD OF DEEP LO TRACKING TO THE W AND ECMWF FCST H85 TEMPS AOA 0C AT 00Z FRI. THEN COLDER FRI-SAT WITH CYC WNW FLOW TO THE S OF LO IN ONTARIO BRINGING LES CHCS. COORDINATED WITH GRB. && .MQT WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING 08Z SUN-00Z TUE MIZ012. WINTER STORM WARNING 12Z SUN-00Z TUE MIZ011-013. SNOW ADVY 12Z SUN-00Z TUE MIZ010. GALE WARNING ALL OF LAKE SUPERIOR. GALE WARNING LAKE MICHIGAN NEAR SHORE AREAS. && $$ ROLFSON (UPDATE) KC/KF (PREV DISCUSSION)
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
1146 AM CST FRI FEB 23 2007 ...MAJOR WINTER EVENT STILL ON TAP FOR THE TRI-STATE... .UPDATE... HERE IS WHAT WE KNOW RIGHT NOW. PROFILERS/RUC 295K THETA SURFACE SHOWING TREMENDOUS WARM ADVECTION/ISENTROPIC LIFT DRIVING BANDS OF ACCAS ACROSS MN/IA/WI THIS MORNING. SATURATION BEGINNING TO OCCUR IN A FEW PLACES BRIEFLY THIS MORNING...WITH KALO REPORTING SOME SNOW AND MEDIA REPORTS INDICATING SOME SLEET/GRAUPEL NEAR MASON CITY. FLURRIES HERE AT WFO ARX. TAMDAR SOUNDINGS FROM MASON CITY AT 16Z SHOWS SATURATION AHEAD OF SCHEDULE AND NOT AS WARM AS RUC/WRF FORECASTS. AS MOISTURE ON THE 295K SURFACE CONTINUES TO SURGE IN...THERMODYNAMIC LIFT /PER 15Z RUC AND 12Z GFS/WRF/ SHOULD INCREASE WITH SATURATION OCCURRING RIGHT OVER ARX CWA LATER THIS AFTERNOON...WITH SNOW THEN INCREASING IN INTENSITY AS ENTIRE LOW/MID LEVEL CONVERGENCE SIGNAL SEEN IN PROFILERS/WIND FIELDS MOVES ACROSS CWA TONIGHT. COULD BE SOME INTENSE SNOW RATES THIS EVENING THROUGH ARX CWA...THUS WARNINGS IN PLACE ALREADY LOOK GOOD...FOR A BURST OF 2-5 OF SNOW. MODELS SHOWING SOME TAPER TO THE QPF THIS PART OF THE EVENT LATE TONIGHT/SATURDAY MORNING AS THIS QPF MOVES NORTH...BUT WONDER IF THAT WILL REALLY OCCUR GIVEN MOISTURE STREAMING INTO AREA FURTHER YET...AND ISENTROPIC LIFT CONTINUING. SECOND SURGE OF HEAVY /DEFORMATION AND FRONTOGENETICAL/ PCPN STILL ON TAP SPREADING IN FROM SOUTH TO NORTH DURING AFTERNOON AND THROUGH SATUDAY NIGHT INTO SUNDAY MORNING. MOST OF THE SNOW WILL FALL THIS PERIOD. FCST SOUNDINGS STILL SUPPORT THREAT OF MIX/SLEET/FREEZING RAIN IN MOST OF NERN IA INTO PORTIONS OF SERN MN. THIS WILL TEMPER SNOW AMOUNTS GREATLY...BUT ALL LOCATIONS WILL GO TO SNOW BY TOMORROW EVENING. COULD BE SIGNIFICANT ICE IN CCY TO OLZ LINE. IT WILL BE THE CUSP OF THIS MIX TO SNOW LINE THAT REALLY SEES THE HEAVY SNOW. BOTTOM LINE...WE THINK PROBABILITIES OF 8 INCHES OF SNOW ARE PRETTY GOOD FOR MOST OF THE CWA...WITH SOME AREAS CERTAIN TO BE CLOSE TO FOOT GIVEN THE MAGNITUDE OF MOISTURE FLUX/DURATION INTO THE SYSTEM. LOCATION IS KEY. ALL OF NORTHEAST IOWA INTO THE RST/PRESTON AREAS WIL RUN THE RISK OF GOING TO SLEET/FZRA FOR A TIME THROUGH SAT AFTN...WHICH MAY KILL SNOW AMOUNTS SOME. FAR SWRN CWA MAY BE SETTING UP FOR SIG ICE DEPENDING ON AMOUNT OF WARMING. RIGHT NOW....HIGHEST CONFIDENCE IN HEAVIEST SNOWS ARE FROM WINONA THROUGH LSE TO SPARTA. FAR ERN/NERN CWA MAY BATTLE DRY AIR THROUGH SATURDAY THUS SNOW AMOUNTS WILL BE LOWER TO START THESE AREAS. WE WILL BE TAKING THE REST OF THE ARX CWA TO WINTER STORM WARNING. I WANT TO EXPRESS CONCERN TO OUR MEDIA PARTNERS/USERS OF THE INCREASING /DANGEROUS/ WIND SIGNAL CROPPING UP AS THE HUDSONS BAY HIGH ANCHORS TO OUR NORTHEAST...AND DYNAMIC LOW COMES OUT OF THE PLAINS. NEW 12Z RUNS OF GFS/WRF SHOWING WINDS ONLY TO INCREASE WITH TIME...WITH SAT AFTN/EVE WINDS OF 60KTS AT 900-850MB. BUFR SOUNDINGS SHOWING SUSTAINED WINDS FROM 20 TO 30 MPH...WITH GUSTS TO 35. THIS MAY CAUSE A ROYAL MESS SATURDAY AFTERNOON AND NIGHT. WE MAY END UP WITH SOME LOCALES IN BLIZZARD CRITERIA IN TIME. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY FOR WIZ017-WIZ029-WIZ032-WIZ033-WIZ034-WIZ041-WIZ042-WIZ043- WIZ044-WIZ053-WIZ054-WIZ055-WIZ061. MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY FOR MNZ079-MNZ086-MNZ087-MNZ088-MNZ094-MNZ095-MNZ096. IA...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 6 PM CST SUNDAY FOR IAZ008-IAZ009-IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030. && $$ BINAU
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1055 PM CST SAT FEB 24 2007 .UPDATE... 855 PM CST UPDATED THE GRIDS AND ZONES TO ACCOUNT FOR NEW LAYOUT TO WINTER STORM WARNING VS. ICE STORM WARNING. BURST OF HVY SNOW WITH RATES OF 1 TO 2 INCHES PER HR OCCURRING WITH BAND NOW MOVING ACROSS FAR N AND NW SUBURBS OF CHICAGO. MIXED BAG OF LIGHTER SN AND FREEZING RAIN BEHIND THIS...THOUGH PRECIP IS MAINLY FREEZING RAIN OVR NW INDY. TEMPS WARM AS DEEP LOW NOW NR KANSAS CITY PUMPS WARM MOIST AIR NWD INTO NRN IL/NW INDY. PRECIP SHOULD TRANSITION FROM A MIX WHICH IS PREDOMINANTLY SNOW NOW...TO MORE OF A SLEET AND FREEZING RAIN SITUATION BY EARLY MORNING AS ELEVATED WARM LAYER AROUND H9 SURGES TO 2-3C ABV FREEZING. HANDEL && .DISCUSSION AFTERNOON FORECAST STRONG RAPIDLY OCCLUDING LOW OVER CENTRAL KANSAS DESTINED TO MOVE TOWARD NRN ILL LATER SUN AND MON BUT BE FILLING OVER TIME. INITIAL CONCERN HOWEVER IS APPROACHING BAND OF RAIN THROUGH CENTRAL ILL. SFC TEMPS ACROSS FCST AREA HAVE INCHED TOWARD 30-32F TODAY BUT HAVE STRONG CONCERNS ABOUT CONTINUING FEED OF DRY AIR FROM EAST. ONCE PRECIP FALLS INTO THIS ZONE THE WET BULB TEMP WILL BE REACHED WHICH IS WELL BELOW 32F. THUS ANY PROGRESS IN WARMING TODAY WILL BE OFFSET BY EVAP COOLING MUCH LESS DARKNESS. FOCUS OF APPROACHING PRECIP AREA APPEARS TO BE SINKING TOWARD THE OHIO VALLEY BUT MODELS SUGGEST VERY STRONG WARMING ALOFT WITH MARKED VEERING SIGNATURE IN MODEL AND ACARS WIND FIELDS. THIS SHOULD FORCE A PERIOD OF STEADY POTENTIALLY MODERATE RAIN FOR A FEW HOURS THIS EVENING BEFORE AREA IS OVER RUN BY A DEVELOPING DRY SLOT /ALOFT/ FROM SW. TIMIMG STILL ON TRACK FOR MAIN EVENT BETWEEN 00Z AND 06Z THIS EVENING. SOME MIX OF PRECIP IS LKLY MAINLY SLEET OVER SRN AND CENTRAL FCST AREA WITH SNOW AND SLEET FURTHER N ALONG THE WISCONSIN BORDER. ANY SNOW AMOUNTS WILL BE HELD DOWN BY PRECIP MIX. WITH LOW TRACKING OVERHEAD LATER SUN AND MON AIRMASS WITH COOL AND LINGERING PRECIP WILL BE TURNED TO SNOW. CANT RULE OUT AREAS OF LIGHT SNOW ACCUMULATION MAINLY SUNDAY NIGHT AND MONDAY AS UNDERMINED IMPULSES PIVOT AROUND DECAYING SYSTEM. IT WILL BE MID WEEK BEFORE SUSTAINED CLEARING OCCURS. UPPER AIR PATTERN SHOWS THE APPROACHING LOW RUNNING HEAD LONG INTO A TEMPORARY BLOCKING PATTERN WHICH ACCOUNTS FOR THE SLUGGISH RETREAT. HOWEVER THIS SITUATION WONT LAST LONG AND ANOTHER SIMILAR HIGH AMPLITUDE TROUGH FCST TO SWING THROUGH THE AREA ABOUT THUR-FRI. THIS TIME NO ICE. NEXT 12HRS WILL BE CRITICAL FOR FORECAST AREA. GIVEN EXPECTATION OF SUBFREEZING SFC TEMPS THROUGH AT LEAST THE FIST PART OF THE NIGHT AND POTENTIAL INTENSITY OF RAIN THE COURSE OF LEAST REGRET DICTATES AN ICE STORM WARNING FOR THE CENTRAL 2/3 OF FCST AREA WITH A WINTER STORM WARNING ALONG THE WISC BORDER...MAINLY FOR SNOW AND SLEET SOME FRZG RAIN. SOUTHERN THIRD OF AREA WILL CONTINUE A FREEZING RAIN ADVISORY. ALL ARE 6PM THIS EVENING TO 6AM SUNDAY. EXPECT MOST INTENSE PRECIPITATION DURING FIRST 6HRS THIS EVENING. DRYING ALOFT LATER IN THE NIGHT MAY REDUCE PRECIP TO DRIZZLE. THRESHOLD FOR ICE STORM IS QUARTER INCH OF ICE AND WITH EXPECTED INTENSITY OF RAIN THIS LEVEL MAY BE REACHED IN MANY SPOTS. TEMPS COULD STRUGGLE ABOVE FREEZING LATER TONIGHT IN WARNING AREA...AND LIKELY BE IN LOW TO MID 30S ON BY SUNDAY AFTERNOON. THIS IS ONE OF THE MORE CHALLENGING FCST SITUATIONS OF RECENT MEMORY. KML && .AVIATION... 1055 PM CST MAJOR WINTER STORM SYSTEM MOVING NE FROM THE CNTRL PLAINS INTO NRN IL BY AFTN SUNDAY. PLENTY OF GULF MSTR MOVING THIS WAY AND OVERRUNNING WARM FNT. RAIN FALLING FROM WARM LAYER TO ENTRENCHED FRZN LAYER RESULTING IN FREEZING RAIN AND SLEET WITH SNOW MORE PREVALENT NORTH. AS WARM LAYER INTRUDES OVERHEAD RFD AND ORD...SNOW CUD MIX OR CHANGE TEMPORARILY TO SLEET OR FRZG RAIN OVERNIGHT. DAYTIME WARMING SUNDAY AT SFC MAY ALLOW JUST RAINFALL IF WARM LAYER REMAINS INTACT OVERHEAD. HOWEVER DURING AFTN...COLD WRAPARND TEMPS UNDERCUTTING AND WEAKENING UPR LOW AND PROBLY RETURNING OR BECOMING ALL SNOW BY END OF DAY. IFR CIGS AND VSBY WILL BE FREQUENTLY IN THE TEMPO GROUP IF NOT PREDOMINANT NEXT 24 HRS. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH ACROSS AREA. IF EVER A DAY TO THINK HARD ABOUT NOT FLYING...THIS IS IT. RLB && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WARNING NORTH AND WEST OF COOK-LASALLE CNTY LINE THROUGH NOON SUN ICE STORM WARNING IROQUOIS-FORD-LIVINGSTON-KANKAKEE TIL 6AM SUN .IN...ICE STORM WARNING TIL 6AM CST /7AM EST/ SUN. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
115 AM EST SUN FEB 25 2007 ...DESTRUCTIVE ICE STORM TONIGHT... .AVIATION... CONTINUED SIG SFC ICING ACROSS NRN INDIANA THROUGH EARLY AM HOURS. STRONG 300K ISENT LIFT WITH ABUNDANT MOISTURE TAP INTO 4-5.5 G/KG AIR ALONG OHIO RIVER. SHARP BAROCLINIC ZONE JUST TO SOUTH ONLY SLOWLY WORKING NORTHEAST NEXT FEW HOURS WITH STRONG BACKED ERLY FLOW TO KEEP PTYPE PREDOMINANTLY ZR AND IP. PRECIP INTENSITY TO DECREASE BETWEEN 08-10 UTC AS BEST LLJ/ISENT UPGLIDE VEERS INTO UPPER OHIO RIVER VALLEY COINCIDENT WITH ARRIVAL OF DRY SLOT CURRENTLY OVER CENTRAL IL AND SUBSEQUENT RAPID DECREASE OF MOISTURE DEPTH. AT KFWA BL WARMS SUFFICIENTLY FOR LIQUID PTYPE BY DAYBREAK AND A FEW HOURS LATER AT KSBN. GREATER MOISTURE DEPTH AT KSBN TO ALLOW FOR PERIODS OF ICE NUCLEATION FOR LIGHT MIX OF DZ AND SN AT TIMES. CIGS TO LOWER TO AT LEAST IFR WITH INCREASED MOISTURE TRANSPORT AS LL WINDS VEER AND WEAKEN CONSIDERABLY AS STACKED CYCLONE OCCLUDES/WEAKENS. && .UPDATE... TREMENDOUS ICE STORM IN PROGRESS ACRS SRN CWA ATTM W/REPORTS OF HEAVY ICING ALREADY W/SOME POWER OUTAGES FM VALPO TO MONTICELLO TO PERU. DEEP LAYERED CYCLONE OVR NE KS WILL SLOWLY EDGE EWD OVERNIGHT AND BACK LL FLW FURTHER. DEEP LOW/MID LVL MSTR PLUME ACRS IL/SW IN WILL SHIFT EWD AND AIDE NEWD EXPANSION OF FZRA AND SLEET INITIALLY AND THEN GIVING WAY TO MAINLY FZRA AFT 05Z SW HALF PER 00Z RUC AND RECENT TAMDAR SOUNDING OUT OF KFWA. EXCEPTION MAY BE FAR NE WHERE DEEPEST LL COLD AIR RESIDES AND EXPECT SNOW SLEET MIX THERE CHANGING TO MAINLY FZRA LATE. SFC OBS/RADAR INDICATE FM .1-.2 INCH PER HOUR ICE ACCRETION RATES WILL CONT THROUGH 09Z. TOP END ICE ACCUMULATIONS MAY END UP HIGHER THEN GOING 3/4 MENTION IN WSW/ZFP BUT CLOSE. SRN CWA WILL CONT TO SLOWLY WARM TO ABV FREEZING AS SFC WINDS BACK W/MID 30S NOTED NOW ACRS CNTRL INDIANA. WILL WAIT FOR THAT TO HAPPEN BFR MAKING ANY DECISION ON SCALING BACK GOING WARNINGS. WILL CONT TO MONITOR BUT SO FAR FCST PLAYING OUT AS XPCD W/NO EARLY UPDATES PLANNED AT THIS TIME. && .SHORT TERM... SHORT/DELAYED DISCUSSION DUE TO MULTIPLE ISSUES. SLEET AND FREEZING RAIN HAS BEEN SLOWLY OVERSPREADING ILLINOIS MUCH OF THE DAY. SOME LOCATIONS IN WESTERN ILLINOIS HAVE ALREADY REPORTED UPWARDS OF A HALF INCH OF ICE. OVER THE PAST HOUR THE AREA OF PRECIP HAS ACCELERATED NE AND HAS REACHED WHITE COUNTY WITH A MIXTURE OF SLEET AND RAIN. WARMER SFC TEMPERATURES ALREADY POISED TO MOVE INTO FAR SOUTHWEST COUNTIES POSSIBLY BY THE OVERNIGHT HOURS. INCREASINGLY DIFFICULT FORECAST AS A RESULT...REQUIRING EXPANDING THE ICE STORM WARNING FURTHER NORTH TO ALONG AND SOUTH OF US 6. ICE ACCUMULATIONS OF ONE HALF TO THREE QUARTERS OF AN INCH OR MORE ARE EXPECTED...ESPECIALLY ACROSS THE NORTHERN HALF OF THE ICE STORM WARNING AREA. WHILE ACCUMULATIONS WILL BE HEAVY FURTHER SOUTH...TEMPS POSSIBLY CLIMBING ABOVE FREEZING WILL ALLOW A STOP TO THE ACCUMULATION OF ICE. EXACTLY WHEN THIS OCCURS REMAINS IN QUESTION...HENCE NO CHANGES TO THE WARNING. FURTHER NORTH...MIXTURE OF SNOW...SLEET AND FREEZING RAIN WILL CAUSE LOTS OF PROBLEMS. ICE ACCUMS OF UP TO QUARTER INCH AS WELL AS SLEET UP TO ONE HALF INCH ARE EXPECTED TONIGHT. IF TREND CONTINUES ON WARMER AIR BEING DRAWN NORTH...THEN SIGNIFICANT ICING COULD ALSO OCCUR ACROSS THE WINTER STORM WARNING AREA. ON SUNDAY...GRIDS CHANGED TO REFLECT THE WARMER AIR ARRIVING WITH EITHER RAIN OR RAIN/SNOW EVENTUALLY DOMINATING SOUTHERN QUARTER TO HALF OF CWA. WILL LEAVE REST OF DETAILS TO LATER SHIFTS. && .LONG TERM... SUNDAY NIGHT THROUGH SATURDAY... FORECAST PERIOD BEGINS WITH STACKED SYSTEM OVER THE AREA. MODELS DIFFERING ON EXACT PLACEMENT WITH NAM FURTHER WEST BACK OVER IOWA AND ILLINOIS SUNDAY NIGHT AND GFS OVER SOUTHERN GREAT LAKES. MODEL SOUNDINGS INDICATING SE CWA MAY SEE BRIEF PERIOD OF LIQUID PRECIP IN THE EVENING BEFORE CHANGING TO SNOW OTHERWISE GOING FORECAST OF SNOW REST OF CWA LOOKS GOOD. STACKED SYSTEM REMAINS OVER THE AREA MONDAY...NOT LOOKING FOR MUCH DIURNAL CHANGE IN TEMPS SO WILL KEEP HIGHS NEAR FREEZING OVER CWA...COLUMN SATURATED THROUGH 700MB AND SUFFICIENTLY COLD TO SUPPORT ICE PRODUCTION AT CLOUD LEVEL SO SHOULD BE ALL SNOW EVEN IF SOME LOCATIONS MANAGE TO NUDGE ABOVE FREEZING. SYSTEM EVENTUALLY KICKS EAST ALLOWING FOR UPSTREAM RIDGING TO WORK INTO THE AREA GIVING DRY FCST TUE NITE AND WEDNESDAY. NEXT SYSTEM THEN DIGS INTO THE PLAINS BRINGING ANOTHER CHANCE FOR PRECIP THURSDAY AND FRIDAY. WILL STAY WITH CURRENT GRIDS RA/SN MIX DURING THE AFTERNOON AND SN NITE/MORNING HOURS. EXPECT TEMPS 5-10 BELOW NORMAL TUE THEN NEAR NORMAL REMAINDER OF EXTENDED....WITH BEST CHANCE OF ABOVE NORMAL TEMPS ON THU IN ADVANCE OF NEXT SYSTEM. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...ICE STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR INZ008-009-018-026-027-033-034. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR INZ006-007. WINTER STORM WARNING UNTIL 12 PM EST /11 AM CST/ SUNDAY FOR INZ003>005. ICE STORM WARNING UNTIL 12 PM EST /11 AM CST/ SUNDAY FOR INZ012>017-020-022>025-032. MI...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR MIZ079>081. WINTER STORM WARNING UNTIL 12 PM EST SUNDAY FOR MIZ077-078. OH...ICE STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR OHZ004-005-015-016-024-025. WINTER STORM WARNING FROM 9 PM THIS EVENING TO 12 PM EST SUNDAY FOR OHZ001-002. LM...BRISK WIND ADVISORY UNTIL 5 PM EST SUNDAY FOR LMZ043-046. && $$ UPDATE...HOLSTEN SHORT TERM/...FISHER LONG TERM...LOGSDON AVIATION...MURPHY
AREA FORECAST DISCUSSION
NWS SEATTLE WA
910 PM PST SAT FEB 24 2007 .SYNOPSIS...A COLD UPPER LEVEL TROUGH WILL REMAIN OFF THE COAST THROUGH MIDWEEK...BRINGING COOL AND SHOWERY WEATHER TO THE REGION. && .SHORT TERM...ANOTHER ROUND OF SHOWERS HEADED OUR WAY LATE THIS EVENING AS A BAND ROTATES ONSHORE THAT IS ASSOCIATED WITH A COLD UPPER LOW OFF THE COAST. FROM SATELLITE DERIVED TRAJECTORIES IT LOOKS LIKE WE WILL HAVE THESE MORE WIDESPREAD SHOWERS AROUND THROUGH A GOOD PORTION OF THE NIGHT. TEMPERATURES ACROSS THE AREA RANGE FROM THE MID 30S TO THE MID 40S AND ACARS DATA INDICATES THAT THE FREEZING LEVEL IS UP AROUND 4000 FEET...SO THE THREAT FOR LOWLAND SNOW IS RATHER LOW TONIGHT. HOWEVER AS THE RATHER COLD OFFSHORE UPPER LOW GRADUALLY WORKS INLAND INTO EARLY WEDNESDAY...THE THREAT OF SOME LOWLAND SNOW SHOWERS INCREASES. THIS WILL BE HIT AND MISS AND MOST LIKELY DURING THE OVERNIGHT HOURS. JUST DON`T BE SURPRISED IF YOU WAKE UP ONE THE NEXT FEW DAYS AND FIND A SKIFF OF SNOW ON THE GRASS. HOPEFULLY (AS FAR AS I`M CONCERNED) THAT THIS IS WINTER`S LAST GASP. THE CURRENT FORECAST HAS THE CURRENT AND SHORT TERM THOUGHTS WELL IN HAND SO AT THIS POINT WON`T UPDATE BASED ON THAT. CURRENTLY HAVE A SNOW ADVISORY UP FOR THE MOUNTAINS UNTIL 10 PM AND THINGS HAVE SETTLED DOWN THERE FOR THE MOMENT. THERE WILL BE ANOTHER BATCH OF SHOWERS THAT WILL AFFECT THE AREA OVERNIGHT...HOWEVER NEW ACCUMULATIONS NOT EXPECTED TO REACH ADVISORY CRITERIA. WILL GO WITH AN ADDITIONAL 4-6 INCHES OVERNIGHT AND LET THE ADVISORY DIE A NATURAL DEATH. CERNIGLIA .LONG TERM...LITTLE CHANGE WEDNESDAY AS UPPER TROUGH TAKES THE SLOW TRAIN EAST THROUGH CWA. SLOW INCREASE IN HEIGHTS AFTER THAT WITH WHAT LOOKS LIKE A SOLID RAIN EVENT SHAPING UP FOR FRIDAY. MORE SHOWERS SATURDAY. BURKE && .AVIATION...LOW PRESSURE REMAINING OFFSHORE. BAND OF SHOWERS MOVING THROUGH WESTERN WASHINGTON 04Z-10Z. AFTER THAT SKIES CLEARING OUT A BIT BEFORE THE SHOWERS REDEVELOP WITH THE UNSTABLE AMS SUNDAY AFTERNOON. .KSEA...SCATTERED TO BROKEN LAYER NEAR 3000 FEET WITH ANOTHER LAYER NEAR 6000 FEET. AFTER 10Z CONDITIONS IMPROVING WITH SCATTERED CLOUDS ABOVE 5000 FEET. CONDITIONS LOWERING TO 3000 TO 4000 FOOT BROKEN MIDDAY INTO EARLY AFTERNOON SUNDAY. WINDS SELY 6 TO 10 KNOTS BECOMING MORE SOUTHERLY SUNDAY AFTERNOON. FELTON .AVALANCHE...FROM PREVIOUS DISCUSSION...PLENTY OF LOW DENSITY SNOW RECEIVED DURING PAST FEW DAYS IS BEING LOADED AND STRESSED BY INCREASINGLY DENSE AND SLIGHTLY WARMER WIND DRIVEN SNOWFALL. THOUGH VISIBILITY POOR, FIELD REPORTS FROM SKI PATROL INDICATE RAPIDLY GROWING CORNICES AND SOME EASY SKI TRIGGERED SLABS RELEASING UP TO 2-3 FEET, MAINLY IN WIND AFFECTED TERRAIN. THIS SNOWPACK SENSITIVITY APPEARS TO BE VERIFYING AVALANCHE WARNING FOR INCREASINGLY UNSTABLE SNOWPACK, ESPECIALLY ABOVE 4-5000 FEET. AS WE TURN MORE SHOWERY LATER SATURDAY, EXPECT SLIGHT DECREASE IN DANGER AND WILL ALLOW WARNING TO EXPIRE TONIGHT. HOWEVER, WITH MORE SNOWFALL ACCOMPANYING ANOTHER, THOUGH WEAKER, SYSTEM SUNDAY, EXPECT ONLY A LIMITED DECREASE IN THE DANGER THROUGH THE WEEKEND WITH DANGER LEVELS HOVERING JUST BELOW WARNING CRITERIA. NO DOUBT THERE IS SOME QUALITY POWDER OUT THERE, JUST HOPE THAT BACK COUNTRY TRAVELERS ADJUST THEIR ROUTES, AND BE A LITTLE MORE CONSERVATIVE FOR AWHILE. FOR DETAILS SEE WWW.NWAC.US. MOORE THIS SECTION IS PROVIDED IN PARTNERSHIP WITH THE USDA FOREST SERVICE NW WEATHER AND AVALANCHE CENTER. && .SEW WATCHES/WARNINGS/ADVISORIES... ...SNOW ADVISORY FOR THE CASCADES AND OLYMPICS TIL 10 PM. ...SMALL CRAFT ADVISORY COAST...WEST AND EAST ENTRANCE TO THE STRAIT...ADMIRALTY INLET...AND THE NORTHERN INLAND WATERS. ...SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS HARBOR BAR. $$ WEATHER.GOV/SEATTLE
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
824 AM CST SUN FEB 25 2007 .MORNING UPDATE... QUICK UPDATE THIS MORNING TO DROP THE WINTER STORM WARNING AS TEMPS HAVE WARMED INTO THE MID/UPPER 30S ALONG WITH LIGHT/MODERATE RAIN ACROSS THE AREA. LEFT THIS AFTERNOON ALONE AS HAVEN/T HAD MUCH TIME TO LOOK AT THE REST OF THE DAY BUT SUSPECT PRECIP TYPE TO BE MAINLY RAIN THRU THE AFTERNOON THOUGH SOME LIGHT SNOW BY EVENING IS POSSIBLE. THUS MAY NEED TO PULL SNOW ACCUMULATIONS FOR THIS AFTERNOON WITH LATE MORNING UPDATE. CMS && .DISCUSSION... THE LOW WAS OVER CENTRAL IOWA AT 09 UTC. ANALYSIS OF THE TEMPERATURE AND WIND ON THE SURFACE SHOWS SOME WARM AIR ADVECTION INTO FORECAST AREA OF NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE RADAR AND SATELLITE IR PICTURES SHOW THE DRY SLOT OVER ILLINOIS AND INDIANA. THERE IS AN AREA OF SHOWERS MOVING INTO CENTRAL ILLINOIS AT 10 UTC. THE LATEST ACARS SOUNDING SHOW THE WARMEST LAYER OVER ROCKFORD IS FROM 918 TO 841 MB AND IS JUST BELOW FREEZING. THE WARMEST LAYER OVER ORD WAS 886 TO 856 MB AND JUST ABOVE FREEZING. THE FORECAST FROM THE GFS MODEL SHOWS THE 500 MB CLOSED CIRCULATION OVER NORTHERN ILLINOIS BY 00 UTC MONDAY. THERE IS ENOUGH POSITIVE VORTICITY ADVECTION TO CREATE ENOUGH LIFT FOR SHOWERS TODAY AND TONIGHT. THE SURFACE LOW IS FORECAST TO FILL AND MOVE INTO MICHIGAN. COLDER AIR WILL RETURN TO THE FORECAST AREA TONIGHT. WE WILL FORECAST A CHANCE OF LIGHT SNOW TONIGHT FOR THE FORECAST AREA. WE WILL CANCEL THE ICE WARNING. THE SURFACE TEMPERATURE HAVE RISEN TO THE MIDDLE AND UPPER 30S. A LOT IS EXPECTED TO MELT TODAY. THERE WILL STILL BE SOME FREEZING DRIZZLE...SLEET AND RAIN IN THE NORTHERN THIRD OF OUR CWA. ISENTROPIC LIFT WITH POSITIVE VORTICITY ADVECTION WILL PROVIDE THE UPWARD VERTICAL MOTION FOR THE PRECIPITATION. DID NOT MAKE MANY CHANGE FOR THE REST OF THE WEEK. THE CLOSED UPPER AIR CIRCULATION REMAINS OVER WISCONSIN UNTIL TUESDAY. THEN ON WEDNESDAY A 500 MB RIDGE MOVES INTO ILLINOIS. THE HIGH TEMPERATURE MAY REACH THE MID 40S. THE CHANCE OF PRECIPITATION WILL EXIST DUE TO THE WARM AIR RETURNING AND OVERRUNNING AND THEN ANOTHER LARGE TROUGH APPROACHES ILLINOIS AND INDIANA THURSDAY AND FRIDAY. THIS WILL RESULT IN A CHANCE OR PRECIPITATION BOTH DAYS. && .AVIATION DISCUSSION FOR 12Z TAFS... 545 AM CST THE CENTER OF THE MAJOR WINTER STORM SYSTEM MOVING TO THE ENE FROM SERN IOWA...AND THRU NRN ILLINOIS TODAY. THIS WILL PROVIDE DIFFICULTIES FOR THE WIND DIRECTION FORECAST AS THE PATH OF THE SFC LOW WILL BE RIGHT OVER THE TAF SITES TODAY. HAVE GONE WITH WINDS STARTING OUT SELY AND GRADUALLY SHIFTING SLY AND THEN WLY THIS EVENING WITH THE CENTER OF THE LOW PASSING TO THE NORTH OF THE TAF SITE. WINDS WL REMAIN ARND 15KT TODAY WITH FREQUENT GUSTS TO 20-25KT DURG THE LATE MORNING AND AFTERNOON HRS. WIND SPEEDS WL DROP OFF AS THE LOW CENTER PASSES OVER NRN IL AND THEN PICK UP AGAIN AND TURN MORE NWLY LATE IN THE PD. RFD WL SEE THE WIND SHIFT TO NWLY BY AROUND MIDNIGHT AND THE OTHER SITES A LITTLE LATER. LATEST SATELLITE IMAGERY SHOWS THE REGION BEING DRY SLOTTED AT MID LEVELS...BUT LOW LEVEL CLOUDINESS IS HANGING IN OVER THE AREA WITH CIGS AT OR JUST SLIGHTLY ABV IFR LEVELS. MOISTURE PROFILES SHOW NEAR SATURATION AND ABV FREEZING TEMPS THROUGH THE LOWER LAYERS... WOULD EXPECT ANY PCPN FOR THE FIRST FEW HRS OF THE TAF PD TO BE DZ. THOUGH CIGS ARE JUST ABV IFR AT SOME LOCATIONS...EXPECT THIS WILL NOT LAST LONG AND IFR CIGS WL BE WIDESPREAD BY LATE MORNING. CIGS WILL LIKELY DROP TO LOW IFR BY LATE AFTERNOON AND REMAIN THERE OVERNIGHT. DO NOT EXPECT ANY IMPROVEMENT IN THE CIGS TODAY. LATEST RADAR IMAGERY SHOWS ANOTHER AREA OF RAIN APPCHG NCNTRL IL AND WILL BE INTO NERN IL BY ARND NOON. WITH DYNAMIC COOLING AND ENHANCED DYNAMICS ASSD WITH THE APCHG UPPER LOW...THE RAIN WILL LIKELY BE MIXED WITH SNOW. PCPN SHUD TURN OVER TO ALL SNOW BY LATE AFTN/EARLY EVENING AS THE SYSTEM PASSES OVERHEAD. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH AS WELL ACROSS AREA. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
545 AM CST SUN FEB 25 2007 .DISCUSSION... THE LOW WAS OVER CENTRAL IOWA AT 09 UTC. ANALYSIS OF THE TEMPERATURE AND WIND ON THE SURFACE SHOWS SOME WARM AIR ADVECTION INTO FORECAST AREA OF NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE RADAR AND SATELLITE IR PICTURES SHOW THE DRY SLOT OVER ILLINOIS AND INDIANA. THERE IS AN AREA OF SHOWERS MOVING INTO CENTRAL ILLINOIS AT 10 UTC. THE LATEST ACARS SOUNDING SHOW THE WARMEST LAYER OVER ROCKFORD IS FROM 918 TO 841 MB AND IS JUST BELOW FREEZING. THE WARMEST LAYER OVER ORD WAS 886 TO 856 MB AND JUST ABOVE FREEZING. THE FORECAST FROM THE GFS MODEL SHOWS THE 500 MB CLOSED CIRCULATION OVER NORTHERN ILLINOIS BY 00 UTC MONDAY. THERE IS ENOUGH POSITIVE VORTICITY ADVECTION TO CREATE ENOUGH LIFT FOR SHOWERS TODAY AND TONIGHT. THE SURFACE LOW IS FORECAST TO FILL AND MOVE INTO MICHIGAN. COLDER AIR WILL RETURN TO THE FORECAST AREA TONIGHT. WE WILL FORECAST A CHANCE OF LIGHT SNOW TONIGHT FOR THE FORECAST AREA. WE WILL CANCEL THE ICE WARNING. THE SURFACE TEMPERATURE HAVE RISEN TO THE MIDDLE AND UPPER 30S. A LOT IS EXPECTED TO MELT TODAY. THERE WILL STILL BE SOME FREEZING DRIZZLE...SLEET AND RAIN IN THE NORTHERN THIRD OF OUR CWA. ISENTROPIC LIFT WITH POSITIVE VORTICITY ADVECTION WILL PROVIDE THE UPWARD VERTICAL MOTION FOR THE PRECIPITATION. DID NOT MAKE MANY CHANGE FOR THE REST OF THE WEEK. THE CLOSED UPPER AIR CIRCULATION REMAINS OVER WISCONSIN UNTIL TUESDAY. THEN ON WEDNESDAY A 500 MB RIDGE MOVES INTO ILLINOIS. THE HIGH TEMPERATURE MAY REACH THE MID 40S. THE CHANCE OF PRECIPITATION WILL EXIST DUE TO THE WARM AIR RETURNING AND OVERRUNNING AND THEN ANOTHER LARGE TROUGH APPROACHES ILLINOIS AND INDIANA THURSDAY AND FRIDAY. THIS WILL RESULT IN A CHANCE OR PRECIPITATION BOTH DAYS. && .AVIATION DISCUSSION FOR 12Z TAFS... 545 AM CST THE CENTER OF THE MAJOR WINTER STORM SYSTEM MOVING TO THE ENE FROM SERN IOWA...AND THRU NRN ILLINOIS TODAY. THIS WILL PROVIDE DIFFICULTIES FOR THE WIND DIRECTION FORECAST AS THE PATH OF THE SFC LOW WILL BE RIGHT OVER THE TAF SITES TODAY. HAVE GONE WITH WINDS STARTING OUT SELY AND GRADUALLY SHIFTING SLY AND THEN WLY THIS EVENING WITH THE CENTER OF THE LOW PASSING TO THE NORTH OF THE TAF SITE. WINDS WL REMAIN ARND 15KT TODAY WITH FREQUENT GUSTS TO 20-25KT DURG THE LATE MORNING AND AFTERNOON HRS. WIND SPEEDS WL DROP OFF AS THE LOW CENTER PASSES OVER NRN IL AND THEN PICK UP AGAIN AND TURN MORE NWLY LATE IN THE PD. RFD WL SEE THE WIND SHIFT TO NWLY BY AROUND MIDNIGHT AND THE OTHER SITES A LITTLE LATER. LATEST SATELLITE IMAGERY SHOWS THE REGION BEING DRY SLOTTED AT MID LEVELS...BUT LOW LEVEL CLOUDINESS IS HANGING IN OVER THE AREA WITH CIGS AT OR JUST SLIGHTLY ABV IFR LEVELS. MOISTURE PROFILES SHOW NEAR SATURATION AND ABV FREEZING TEMPS THROUGH THE LOWER LAYERS... WOULD EXPECT ANY PCPN FOR THE FIRST FEW HRS OF THE TAF PD TO BE DZ. THOUGH CIGS ARE JUST ABV IFR AT SOME LOCATIONS...EXPECT THIS WILL NOT LAST LONG AND IFR CIGS WL BE WIDESPREAD BY LATE MORNING. CIGS WILL LIKELY DROP TO LOW IFR BY LATE AFTERNOON AND REMAIN THERE OVERNIGHT. DO NOT EXPECT ANY IMPROVEMENT IN THE CIGS TODAY. LATEST RADAR IMAGERY SHOWS ANOTHER AREA OF RAIN APPCHG NCNTRL IL AND WILL BE INTO NERN IL BY ARND NOON. WITH DYNAMIC COOLING AND ENHANCED DYNAMICS ASSD WITH THE APCHG UPPER LOW...THE RAIN WILL LIKELY BE MIXED WITH SNOW. PCPN SHUD TURN OVER TO ALL SNOW BY LATE AFTN/EARLY EVENING AS THE SYSTEM PASSES OVERHEAD. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH AS WELL ACROSS AREA. KREIN && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WARNING NORTH AND WEST OF COOK-LASALLE CNTY LINE THROUGH NOON SUN .IN...NONE. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
340 AM CST SUN FEB 25 2007 .DISCUSSION... THE LOW WAS OVER CENTRAL IOWA AT 09 UTC. ANALYSIS OF THE TEMPERATURE AND WIND ON THE SURFACE SHOWS SOME WARM AIR ADVECTION INTO FORECAST AREA OF NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE RADAR AND SATELLITE IR PICTURES SHOW THE DRY SLOT OVER ILLINOIS AND INDIANA. THERE IS AN AREA OF SHOWERS MOVING INTO CENTRAL ILLINOIS AT 10 UTC. THE LATEST ACARS SOUNDING SHOW THE WARMEST LAYER OVER ROCKFORD IS FROM 918 TO 841 MB AND IS JUST BELOW FREEZING. THE WARMEST LAYER OVER ORD WAS 886 TO 856 MB AND JUST ABOVE FREEZING. THE FORECAST FROM THE GFS MODEL SHOWS THE 500 MB CLOSED CIRCULATION OVER NORTHERN ILLINOIS BY 00 UTC MONDAY. THERE IS ENOUGH POSITIVE VORTICITY ADVECTION TO CREATE ENOUGH LIFT FOR SHOWERS TODAY AND TONIGHT. THE SURFACE LOW IS FORECAST TO FILL AND MOVE INTO MICHIGAN. COLDER AIR WILL RETURN TO THE FORECAST AREA TONIGHT. WE WILL FORECAST A CHANCE OF LIGHT SNOW TONIGHT FOR THE FORECAST AREA. WE WILL CANCEL THE ICE WARNING. THE SURFACE TEMPERATURE HAVE RISEN TO THE MIDDLE AND UPPER 30S. A LOT IS EXPECTED TO MELT TODAY. THERE WILL STILL BE SOME FREEZING DRIZZLE...SLEET AND RAIN IN THE NORTHERN THIRD OF OUR CWA. ISENTROPIC LIFT WITH POSITIVE VORTICITY ADVECTION WILL PROVIDE THE UPWARD VERTICAL MOTION FOR THE PRECIPITATION. DID NOT MAKE MANY CHANGE FOR THE REST OF THE WEEK. THE CLOSED UPPER AIR CIRCULATION REMAINS OVER WISCONSIN UNTIL TUESDAY. THEN ON WEDNESDAY A 500 MB RIDGE MOVES INTO ILLINOIS. THE HIGH TEMPERATURE MAY REACH THE MID 40S. THE CHANCE OF PRECIPITATION WILL EXIST DUE TO THE WARM AIR RETURNING AND OVERRUNNING AND THEN ANOTHER LARGE TROUGH APPROACHES ILLINOIS AND INDIANA THURSDAY AND FRIDAY. THIS WILL RESULT IN A CHANCE OR PRECIPITATION BOTH DAYS. && .AVIATION... 1055 PM CST MAJOR WINTER STORM SYSTEM MOVING NE FROM THE CNTRL PLAINS INTO NRN IL BY AFTN SUNDAY. PLENTY OF GULF MSTR MOVING THIS WAY AND OVERRUNNING WARM FNT. RAIN FALLING FROM WARM LAYER TO ENTRENCHED FRZN LAYER RESULTING IN FREEZING RAIN AND SLEET WITH SNOW MORE PREVALENT NORTH. AS WARM LAYER INTRUDES OVERHEAD RFD AND ORD...SNOW CUD MIX OR CHANGE TEMPORARILY TO SLEET OR FRZG RAIN OVERNIGHT. DAYTIME WARMING SUNDAY AT SFC MAY ALLOW JUST RAINFALL IF WARM LAYER REMAINS INTACT OVERHEAD. HOWEVER DURING AFTN...COLD WRAPARND TEMPS UNDERCUTTING AND WEAKENING UPR LOW AND PROBLY RETURNING OR BECOMING ALL SNOW BY END OF DAY. IFR CIGS AND VSBY WILL BE FREQUENTLY IN THE TEMPO GROUP IF NOT PREDOMINANT NEXT 24 HRS. ICING AND TURBULENCE WILL BE FREQ HAZARDS ALSO TO CONTEND WITH ACROSS AREA. IF EVER A DAY TO THINK HARD ABOUT NOT FLYING...THIS IS IT. RLB && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...WINTER STORM WARNING NORTH AND WEST OF COOK-LASALLE CNTY LINE THROUGH NOON SUN .IN...NONE. .LM...GALE WRNG ALL LM AND NR SHORES THROUGH SUNDAY NIGHT. && $$
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
102 PM PST SUN FEB 25 2007 .SYNOPSIS... INCREASING ONSHORE FLOW WILL BRING COOLING...GUSTY WINDS IN THE MOUNTAINS AND DESERTS...AND AN INCREASE IN CLOUDINESS WEST OF THE MOUNTAINS THROUGH TUESDAY. EXPECT PATCHY DRIZZLE OR SPRINKLES AT TIMES WEST OF THE MOUNTAINS THROUGH MONDAY NIGHT. THE BEST CHANCE FOR MEASURABLE RAIN AND MOUNTAIN SNOW WILL BE ON TUESDAY INTO EARLY WEDNESDAY AS A TROUGH OF LOW PRESSURE SWINGS THROUGH THE REGION. THEN BREEZY AT TIMES AND CONTINUED COOL THROUGH FRIDAY. SLIGHTLY WARMER BY NEXT WEEKEND. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... SATELLITE SHOWS MARINE STRATUS HAS BEEN INCREASING THROUGHOUT THE DAY. A FEW SHOWERS HAVE BEEN REPORTED IN ORANGE COUNTY ASSOCIATED WITH A SURGE OF STRATUS MOVING DOWN THE COAST. BECAUSE OF THE ADDITIONAL CLOUD COVER...TEMPERATURES WERE RUNNING...ABOUT 5 DEGREES F COOLER THAN YESTERDAY AT NOON. SEVERAL BANDS OF STRATOCU ARE ADVANCING TOWARD THE CA COAST THIS AFTERNOON THAT DO NOT CORRELATE WELL WITH MODEL FEATURES. THIS IS TROUBLESOME AND KEEPS CONFIDENCE LOW FOR THE ONSET OF MEASURABLE PRECIPITATION. FOR NOW ONLY TRACE AMOUNTS ARE EXPECTED. ONSHORE SURFACE PRESSURE GRADIENTS ARE INCREASING...WITH OVER 12 MBS NOW SAN DIEGO TO TONOPAH. WIND GUSTS HAVE INCREASED TO OVER 30 MPH AT SOME REMOTE SENSORS IN THE MOUNTAINS AND NEAR THE BANNING PASS. WITH THE ADDITIONAL CLOUDS AND STRONGER ONSHORE...MAX TEMPERATURES ARE LIKELY TO BE A FEW DEGREES LOWER AGAIN TOMORROW...ESPECIALLY INLAND. WE ARE STILL ON TRACK FOR MORE CLOUDS...WIND...AND LIGHT PRECIP OVER THE NEXT FEW DAYS AS THE POLAR JET PAYS US ANOTHER EXTENDED VISIT THROUGH WED. EXPECT DAYTIME TEMPS TO BE RUNNING FROM 5 DEGREES BELOW AVERAGE NEAR THE COAST...TO 10 DEGREES LOWER FAR INLAND. IN ADDITION...EXPECT A PROLONGED PERIOD OF STRONG AND GUSTY WINDS OVER THE MOUNTAINS...AND IN PORTIONS OF THE DESERTS...AS THE RIVER OF AIR ABOVE US ACCELERATES. THE MOUNTAINS WILL PUT UP A FIGHT...BUT THE ENERGY WILL STILL BE FELT IN THE FORM OF STRONG UPSLOPE FLOW...FOG...AND LIGHT PRECIPITATION ON THE WINDWARD SIDE... AND GUSTY FITS ON THE LEEWARD SIDE WHICH RESULT IN MOUNTAIN WAVES AND ROTORS IN THE DESERTS. A WIND ADVISORY HAS BEEN ISSUED THROUGH WED...BUT IT MAY HAVE TO BE UPGRADED LATER AS WINDS COULD REACH WARNING CRITERIA BY TUESDAY AND WEDNESDAY AS THE CORE OF THE STRONGEST WINDS ALOFT MOVES OVERHEAD. LATER ON WED THROUGH FRI...THE LONG-WAVE TROUGH MOVES ON TO THE EAST STIRRING UP TROUBLE IN THE MIDWEST. IT LEAVES US IN WEAKENING NW FLOW ALOFT FOR IMPROVING WEATHER...BUT STILL RATHER COOL UNTIL THE WEEKEND WHEN WEAK RIDGING AND OFFSHORE HELP TO WARM US UP SLIGHTLY. IN TERMS OF PRECIPITATION...LOOK FOR PERIODS OF LIGHT RAIN OR DRIZZLE...AND FOG ON THE COASTAL SLOPES TONIGHT THROUGH WED. FARTHER WEST TO THE COAST...OTHER THAN PERIODS OF DRIZZLE AND SPRINKLES NIGHT AND MORNING...OUR BEST CHANCE OF MEASURABLE LIGHT RAIN APPEARS TO BE ON TUE INTO EARLY WED. AMOUNTS LOOK TO BE LESS THAN ONE-HALF INCH TOTAL W OF THE MTNS...BUT COULD BE CONSIDERABLY MORE ON THE COASTAL SLOPES AS AMOUNTS ADD UP INTO WED. THE SNOW LEVEL SHOULD FALL TO AROUND 5K FT ON TUE...AND COULD BE AS LOW AS 3500 FEET WED. EVEN THOUGH SNOWFALL MAY NOT BE HEAVY FOR THE RESORT TOWNS...IT COULD BE AT THE HIGHEST ELEVATIONS. IN ANY CASE...THE COMBINATION OF STRONG WINDS AND REDUCED VISIBILITY IN FALLING AND BLOWING SNOW AND FOG...WILL LIKELY MAKE FOR HAZARDOUS TRAVEL CONDITIONS BY TUE AFTERNOON IF NOT SOONER FOR THOSE VENTURING TO OR THROUGH THE MTNS. && .AVIATION... 251830Z...MARINE LAYER CONTINUES TO DEEPEN OVER THE AREA IN RESPONSE TO A STRENGTHENING ONSHORE FLOW AND A EDDY OVER THE COASTAL WATERS. MID MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER HAD DEEPENED TO AROUND 3000 FEET NEAR KSAN AND SHOULD CONTINUE TO DEEPEN THROUGH THE AFTERNOON. DEPTH COULD REACH 3500 TO 4000 FEET BY EARLY EVENING. BASES SHOULD LIFT AS A RESULT TO AROUND 3000 FEET MSL DURING THE DAY AS WELL. EXPECT BROKEN WITH SOME SCATTERED CONDITIONS INTO THE AFTERNOON BECOMING BROKEN TO OVERCAST BY EARLY EVENING WEST OF THE MOUNTAINS. THE DEEPENING COULD BRING SOME DRIZZLE TO AIRPORTS WEST OF THE MOUNTAINS THIS EVENING AND TONIGHT AS WELL. DEEP MARINE LAYER SHOULD CONTINUE ON MONDAY WITH BASES BETWEEN 2500 AND 3000 FEET AND TOPS TO 5000 FEET. KSAN...KCRQ...KSNA AND KONT...SCATTERED TO BROKEN STRATOCU WITH BASES BASES BETWEEN 3000 AND 3500 FEET MSL THIS AFTERNOON BECOMING BROKEN TO OVERCAST DURING THE EVENING. SOME LIGHT DRIZZLE IS POSSIBLE TONIGHT INTO MONDAY MORNING. KPSP...NO CEILING ISSUES BUT FAIRLY STRONG SOUTHWEST TO WEST WINDS OVER THE MOUNTAINS TO THE WEST COULD BRING MOUNTAIN WAVE/ROTOR ACTIVITY TO THE VICINITY OF THE AIRPORT THIS AFTERNOON THROUGH MONDAY. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...WIND ADVISORY FOR THE THE HIGHER MOUNTAINS AND DESERTS. SEE LAXNPWSGX. PZ...NONE. && $$ PUBLIC...JAD AVIATION/MARINE...HORTON NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1155 AM CST SUN FEB 25 2007 .MORNING UPDATE... 824 AM CST... QUICK UPDATE THIS MORNING TO DROP THE WINTER STORM WARNING AS TEMPS HAVE WARMED INTO THE MID/UPPER 30S ALONG WITH LIGHT/MODERATE RAIN ACROSS THE AREA. LEFT THIS AFTERNOON ALONE AS HAVEN/T HAD MUCH TIME TO LOOK AT THE REST OF THE DAY BUT SUSPECT PRECIP TYPE TO BE MAINLY RAIN THRU THE AFTERNOON THOUGH SOME LIGHT SNOW BY EVENING IS POSSIBLE. THUS MAY NEED TO PULL SNOW ACCUMULATIONS FOR THIS AFTERNOON WITH LATE MORNING UPDATE. CMS && .DISCUSSION... 525 AM CST... THE LOW WAS OVER CENTRAL IOWA AT 09 UTC. ANALYSIS OF THE TEMPERATURE AND WIND ON THE SURFACE SHOWS SOME WARM AIR ADVECTION INTO FORECAST AREA OF NORTH CENTRAL AND NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE RADAR AND SATELLITE IR PICTURES SHOW THE DRY SLOT OVER ILLINOIS AND INDIANA. THERE IS AN AREA OF SHOWERS MOVING INTO CENTRAL ILLINOIS AT 10 UTC. THE LATEST ACARS SOUNDING SHOW THE WARMEST LAYER OVER ROCKFORD IS FROM 918 TO 841 MB AND IS JUST BELOW FREEZING. THE WARMEST LAYER OVER ORD WAS 886 TO 856 MB AND JUST ABOVE FREEZING. THE FORECAST FROM THE GFS MODEL SHOWS THE 500 MB CLOSED CIRCULATION OVER NORTHERN ILLINOIS BY 00 UTC MONDAY. THERE IS ENOUGH POSITIVE VORTICITY ADVECTION TO CREATE ENOUGH LIFT FOR SHOWERS TODAY AND TONIGHT. THE SURFACE LOW IS FORECAST TO FILL AND MOVE INTO MICHIGAN. COLDER AIR WILL RETURN TO THE FORECAST AREA TONIGHT. WE WILL FORECAST A CHANCE OF LIGHT SNOW TONIGHT FOR THE FORECAST AREA. WE WILL CANCEL THE ICE WARNING. THE SURFACE TEMPERATURE HAVE RISEN TO THE MIDDLE AND UPPER 30S. A LOT IS EXPECTED TO MELT TODAY. THERE WILL STILL BE SOME FREEZING DRIZZLE...SLEET AND RAIN IN THE NORTHERN THIRD OF OUR CWA. ISENTROPIC LIFT WITH POSITIVE VORTICITY ADVECTION WILL PROVIDE THE UPWARD VERTICAL MOTION FOR THE PRECIPITATION. DID NOT MAKE MANY CHANGE FOR THE REST OF THE WEEK. THE CLOSED UPPER AIR CIRCULATION REMAINS OVER WISCONSIN UNTIL TUESDAY. THEN ON WEDNESDAY A 500 MB RIDGE MOVES INTO ILLINOIS. THE HIGH TEMPERATURE MAY REACH THE MID 40S. THE CHANCE OF PRECIPITATION WILL EXIST DUE TO THE WARM AIR RETURNING AND OVERRUNNING AND THEN ANOTHER LARGE TROUGH APPROACHES ILLINOIS AND INDIANA THURSDAY AND FRIDAY. THIS WILL RESULT IN A CHANCE OR PRECIPITATION BOTH DAYS. && .AVIATION DISCUSSION FOR 18Z TAFS... 1155 AM CST 993 SFC LOW LOCATED JUST NORTH OF THE QUAD CITIES AT 17Z WILL WITH A WARM FRONT EXTENDING ESE ACROSS NRN IL INTO NRN IN. THE LOW WILL CONTINUE TO DRIFT SLOWLY ENE THIS AFTERNOON AND TONIGHT AND WEAKEN IN RESPONSE TO FILLING UPPER LEVEL LOW. POSITION OF MID LEVEL LOW VERY APPARENT IN WSR-88D DATA OVER NRN IL SLOWLY LIFTING NORTH WITH ASSOCIATED UPPER LEVEL VORTICITY LOBE. NEXT IMPULSE ROTATING AROUND THE PARENT LOW OVER IA RESPONSIBLE FOR NEXT WAVE OF PRECIP/RADAR ECHO RETURNS CURRENTLY SHOWING UP OVER CNTRL IL HEADED NE. EXPECT PRECIPITATION TYPE TO CHANGE BACK FROM RAIN TO A MIX OF RAIN/SNOW AND THEN SNOW AS COLD AIR ADVECTS SE WITH THE LOW. 850 MB (1500 KFT) TEMPS COOL TO -7 TO -8 DEG C BY 00Z ACROSS THE AREA WITH ENTIRE TEMP PROFILE COOLING TO BELOW 0 DEC C PER FORECAST SOUNDINGS. MAY SEE A BRIEF PERIOD OF SLEET MIXED IN AS COOLING TAKES OVER BUT THIS SHOULD BE BRIEF. VISIBILITIES TO REMAIN LOW MVFR OR HIGH IFR NEXT HOUR OR TWO AS LOW AND ASSOCIATED WARM FRONT APPROACHES AND FLOW REMAINS E-SE. AS SFC AND BOUNDARY LAYER FLOW TURNS MORE S AND THEN SW EXPECT VISIBILITIES TO IMPROVE SLIGHTLY BEFORE SNOW COMMENCES. THIS PERIOD WILL BE BRIEF... AND NON-EXISTENT IN LOCATIONS WHERE THE WINDS VEER WHEN OR AFTER THE SNOW SPREADS IN. INTERMITTENT LIGHT SNOW WILL CONTINUE TONIGHT INTO EARLY MONDAY... WITH SNOW ACCUMULATIONS FROM 1-2 INCHES. IFR CIGS WILL PERSIST THROUGH 15Z MONDAY. ED F && .LOT WATCHES/WARNINGS/ADVISORIES... .IL...NONE. .IN...NONE. .LM...GALE WRNG IN EFFECT NORTH HALF OF LM THROUGH 03Z. SMALL CRAFT ADVISORY IN EFFECT FOR IL AND IN NEARSHORE WATERS UNTIL 04Z. && $$