AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
134 PM PST MON FEB 26 2007
.SYNOPSIS...
A LOW PRESSURE TROUGH WILL SLOWLY DROP OVER SOUTHERN CALIFORNIA
THROUGH WEDNESDAY BRINGING A DEEP MARINE LAYER...PERIODS OF LIGHT
RAIN OR DRIZZLE WEST OF THE MOUNTAINS...AND LIGHT TO MODERATE RAIN
AND SNOW IN THE MOUNTAINS. STRONG AND GUSTY WINDS WILL PERSIST AT
THE HIGHER ELEVATIONS OF THE MOUNTAINS...AND IN SPOTS IN THE
DESERTS. TRAVEL COULD BECOME DIFFICULT IN THE MOUNTAINS ON TUESDAY
AND WEDNESDAY DUE TO GUSTY WINDS AND REDUCED VISIBILITY IN SNOW AND
FOG. THE PRECIPITATION SHOULD END ON THURSDAY...BUT IT WILL REMAIN
RATHER COOL THROUGH FRIDAY. THEN DRY AND WARMER FOR THE WEEKEND
UNDER BUILDING HIGH PRESSURE ALOFT.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
MARINE LAYER BACKING UP AGAINST THE COASTAL SLOPES THIS AFTERNOON TO
ABOUT 5K FEET. REMOTE ALERT GAGES ON THE SLOPES INDICATE LIGHT RAIN
HAS BEEN FALLING IN SPOTS...BUT AMOUNTS HAVE BEEN MOSTLY UNDER
ONE-TENTH OF AN INCH OVER THE PAST FEW HOURS. SATELLITE IMAGES ALSO
SHOW LONG ISLAND BANDS STREAMING OFF SANTA CATALINA AND SAN CLEMENTE
CLOUDING UP SOME AREAS OF THE COAST WHILE OTHERS REMAIN MOSTLY
CLEAR. SURFACE PRESSURE GRADIENTS HAVE INCREASED AGAIN INLAND TO
OVER 12 MBS SAN DIEGO TO TONOPAH. A FEW SPOTS IN THE MOUNTAINS AND
DESERTS HAVE BEEN REPORTING GUSTS FROM 35 TO 45 MPH. IN GENERAL...UP
THROUGH NOON...WINDS HAVE NOT BEEN A PROBLEM.
THE MAIN WEATHER CONCERN FOR THE NEXT FEW DAYS WILL BE THE WIND...
EVEN THOUGH PERIODS OF RAIN AND SNOW ARE EXPECTED. THE STRONGEST
WINDS WILL BE CONCENTRATED OVER THE HIGHEST TERRAIN IN THE SAN
JACINTO AND SAN BERNARDINO MOUNTAINS...AND DOWNWIND OVER SPOTS IN
THE DESERTS...WHERE MOUNTAIN WAVES SURFACE. WIND GUSTS IN THESE
AREAS WILL LIKELY EXCEED 50 MPH. OUR LOCAL WIND GUIDANCE INDICATES
HIGH WIND CRITERIA WILL MARGINALLY BE MET IN THE WINDIEST SPOTS SO I
WILL LEAVE THE WARNING IN EFFECT...HOWEVER MOST AREAS WILL LIKELY
EXPERIENCE ADVISORY WINDS AT BEST.
SYNOPTICALLY...A LARGE...LONG-WAVE TROUGH WILL BE MOVING OVER
CALIFORNIA THROUGH WED...SOLIDIFYING THE POLAR AND SUBTROPICAL JETS
INTO ONE STRONG JET CORE EXCEEDING 170 KTS OVER SAN DIEGO. WHILE THE
BULK OF THIS WIND WILL FLY BY OVERHEAD...WINDS LOWER IN THE
ATMOSPHERE WILL BE ACCELERATING FROM THE WEST...WHICH WILL DRIVE THE
UPSLOPE MACHINE ON OUR COASTAL SLOPES FOR A PROLONGED PERIOD OF
LIGHT TO MODERATE PRECIPITATION...FOG AND CLOUDS. AS TEMPERATURES
FALL ON TUE NIGHT AND WED...SOME SNOW IS LIKELY ABOVE 4K FT AS WELL.
THE COMBINATION OF SNOWFALL...WIND...AND FOG WILL MAKE FOR HAZARDOUS
TRAVEL IN OUR MOUNTAINS ON TUE AND WED.
THE UPPER-LEVEL TROUGH AND SCREAMING JET WILL MOVE EAST...INTO THE
MIDWEST WREAKING METEOROLOGICAL HAVOC THROUGH THE MISSISSIPPI VALLEY
AND THE GREAT LAKES...WHILE OUR WEATHER DRIES AND SLOWLY WARMS THU
AND FRI BACK TO NEAR SEASONAL NORMALS. NEXT WEEKEND LOOKS DOWNRIGHT
SPECTACULAR AS TEMPS RISE AND THE SKIES REMAIN CLEAR.
&&
AVIATION...
LATE MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER DEPTH HAD
LOWERED TO AROUND 4000 FEET OVER THE AREA. THE MARINE LAYER IS
EXPECTED TO DEEPEN TONIGHT AND TUESDAY. MULTIPLE LAYERS OF STRATOCU
IS EXPECTED WITH THE LOWEST SCATTERED LOCALLY BROKEN LAYER AROUND
2000 FEET MSL WITH ANOTHER BROKEN LAYER AROUND 3500 FEET MSL.
FAIRLY STRONG WESTERLY WINDS ACROSS THE MOUNTAINS SHOULD PRODUCE
MOUNTAIN WAVE/ROTOR ACTIVITY OVER THE COACHELLA VALLEY THROUGH THIS
EVENING.
KSAN...KCRQ...KSNA AND KONT...SHOULD REMAIN MVFR OR BETTER THROUGH
TONIGHT.
KPSP...MAIN ISSUE WILL BE MOUNTAIN WAVE/ROTOR ACTIVITY. PREDOMINATE
WIND SHOULD BE NORTHWEST BUT COULD GO SOUTHEAST AT TIMES AS A RESULT
OF ROTOR ACTIVITY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FOR THE THE MOUNTAINS AND DESERTS UNTIL 6 PM...
THEN A HIGH WIND WARNING THROUGH WEDNESDAY AFTERNOON. SEE LAXNPWSGX.
SPECIAL WEATHER STATEMENT. SEE LAXSPSSGX.
PZ...NONE.
&&
$$
PUBLIC............JAD
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
912 AM PST MON FEB 26 2007
.SYNOPSIS...
A LOW PRESSURE TROUGH WILL SLOWLY DROP OVER SOUTHERN CALIFORNIA
THROUGH WEDNESDAY BRINGING A DEEP MARINE LAYER...PERIODS OF LIGHT
RAIN OR DRIZZLE...AND STRONG...GUSTY WINDS TO THE MOUNTAINS AND
DESERTS. SEVERAL INCHES OF SNOW COULD FALL IN THE MOUNTAINS ABOVE
4000 FEET ON WEDNESDAY. IT WILL REMAIN RATHER COOL THROUGH FRIDAY
THEN DRY AND WARMER FOR THE WEEKEND UNDER BUILDING HIGH PRESSURE
ALOFT.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
MARINE LAYER LOOKS TO BE ABOUT 6K FT THIS MORNING BASED ON THE 12Z
MIRAMAR SOUNDING AND RECENT VISIBLE SATELLITE IMAGES. CLOUDS ARE
THICKEST UP AGAINST THE COASTAL SLOPES WHERE SOME LIGHT
PRECIPITATION IS BEING REPORTED FROM REMOTE GAGES. THE CLOUDS ARE
BROKEN FARTHER WEST TOWARD THE COAST. SURFACE PRESSURE GRADIENTS
HAVE WEAKENED A BIT FROM YESTERDAY AND WINDS LOOK TO BE BELOW
ADVISORY CRITERIA OVER MOST OF THE AREA...EVEN THOUGH SOME STRONG
GUSTS OVER 30 MPH CONTINUE IN SPOTS IN THE MOUNTAINS AND DESERTS.
THE MAIN WEATHER CONCERN FOR THE NEXT FEW DAYS WILL BE THE WIND...
EVEN THOUGH PERIODS OF LIGHT PRECIPITATION ARE EXPECTED. THE
STRONGEST WINDS WILL BE CONCENTRATED OVER THE HIGHEST TERRAIN IN THE
SAN JACINTO AND SAN BERNARDINO MOUNTAINS...AND DOWNWIND OVER SPOTS
IN THE DESERTS WHERE MOUNTAIN WAVES SURFACE. WIND GUSTS IN THESE
AREAS WILL LIKELY EXCEED 50 MPH AT TIMES.
SYNOPTICALLY...A LARGE...LONG-WAVE TROUGH WILL BE MOVING OVER
CALIFORNIA THROUGH WED...SOLIDIFYING THE POLAR AND SUBTROPICAL JETS
INTO ONE STRONG JET CORE EXCEEDING 170 KTS OVER SAN DIEGO. WHILE THE
BULK OF THIS WIND WILL FLY BY OVERHEAD...WINDS LOWER IN THE
ATMOSPHERE WILL BE ACCELERATING FROM THE WEST...WHICH WILL DRIVE THE
UPSLOPE MACHINE ON OUR COASTAL SLOPES FOR A PROLONGED PERIOD
OF...MOSTLY LIGHT PRECIPITATION...FOG AND CLOUDS. AS TEMPERATURES
FALL ON TUE NIGHT AND WED...SOME SNOW IS LIKELY ABOVE 4K FT AS WELL.
THE COMBINATION OF SNOWFALL...WIND...AND FOG WILL MAKE FOR HAZARDOUS
TRAVEL IN OUR MOUNTAINS ON TUE AND WED.
THE UPPER-LEVEL TROUGH AND SCREAMING JET WILL MOVE EAST...INTO THE
MIDWEST WREAKING METEOROLOGICAL HAVOC THROUGH THE MISSISSIPPI VALLEY
THE GREAT LAKES AND POINTS EAST...WHILE OUR WEATHER DRIES AND SLOWLY
WARMS THU AND FRI BACK TO NEAR SEASONAL NORMALS. NEXT WEEKEND LOOKS
DOWNRIGHT SPECTACULAR AT THIS POINT ANYWAY...AS TEMPS RISE AND THE
SKIES REMAIN CLEAR.
&&
AVIATION...
MORNING ACARS SOUNDINGS INDICATE THE MARINE LAYER DEPTH WAS AROUND
5000 FEET OVER THE AREA. LITTLE CHANGE IN THE DEPTH IS EXPECTED
TODAY BUT THE MARINE LAYER DEPTH IS EXPECTED TO DEEPEN FURTHER
TONIGHT AND TUESDAY. MULTIPLE LAYERS OF STRATOCU IS EXPECTED WITH
THE LOWEST SCATTERED LOCALLY BROKEN LAYER AROUND 2000 FEET MSL WITH
ANOTHER BROKEN LAYER AROUND 4000 FEET MSL.
FAIRLY STRONG WESTERLY WINDS ACROSS THE MOUNTAINS SHOULD PRODUCE
MOUNTAIN WAVE/ROTOR ACTIVITY OVER THE COACHELLA VALLEY THROUGH THIS
EVENING.
KSAN...KCRQ...KSNA AND KONT...SHOULD REMAIN MVFR OR BETTER THROUGH
TONIGHT.
KPSP...MAIN ISSUE WILL BE MOUNTAIN WAVE/ROTOR ACTIVITY. PREDOMINATE
WIND SHOULD BE NORTHWEST BUT COULD GO SOUTHEAST AT TIMES AS A RESULT
OF ROTOR ACTIVITY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FOR THE THE MOUNTAINS AND DESERTS UNTIL 6 PM...
THEN A HIGH WIND WARNING THROUGH WEDNESDAY AFTERNOON. SEE LAXNPWSGX.
SPECIAL WEATHER STATEMENT. SEE LAXSPSSGX.
PZ...NONE.
&&
$$
PUBLIC............JAD
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
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
FLORIDA KEYS AREA FORECAST DISCUSSION
NWS KEY WEST FL
1015 PM EST MON FEB 26 2007
.DISCUSSION...
AS OF 9 PM...SURFACE PRESSURES PLACED A RIDGE AXIS EXTENDING WEST
FROM THE ATLANTIC...ACROSS THE NORTHERN BAHAMAS BETWEEN NASSAU AND
FREEPORT...THEN TO THE SOUTHERN TIP OF THE FLORIDA PENINSULA. THIS
IS A LITTLE FARTHER NORTH THAN WHAT THE GFS MODEL INDICATED FOR THE
CURRENT TIME...AND QUITE A BIT FARTHER NORTH THEN FORECAST BY THE
NAM MODEL. SURFACE WINDS...AS A RESULT...HAVE BEEN PERSISTING FROM
THE SSE OVER KEYS AREAS WELL SOUTH OF THE RIDGE AXIS INSTEAD OF
TURNING TO SSW AS EXPECTED. HOWEVER...DESPITE THE SURFACE WINDS...
WINDS JUST ABOVE THE SURFACE ARE SSW 15 KT OR SO ACCORDING THE THE
CUDJOE KEY WIND PROFILER AND THE KEY WEST EVENING SOUNDING. THE
AIRMASS IS MORE MOIST THIS EVENING...WITH PRECIPITABLE WATER
MEASURED 1.69 INCHES...AND A WEAK CAP THAT HAD BEEN IN PLACE AROUND
8 THSD FT IS MOSTLY GONE FOR NOW. THE AIRMASS SUPPORTED AFTERNOON
SHOWERS AGAIN OVER CUBA...AND EVEN SOME THUNDERSTORMS OFF THE EAST
CENTRAL CUBAN COAST. THESE SHOWERS HAVE RECENTLY DISSIPATED AFTER
HAVING MOVED NORTHEAST INTO FLORIDA STRAITS WATERS. CURRENTLY...
THE RADAR SCOPE IS CLUTTERED BY SOME LEFT-OVER DEPARTING MILITARY
CHAFF OVER THE UPPER KEYS...A FEW SMALL SHOWERS OUT IN THE STRAITS...
AND A STREAK OF MID CLOUDS (MAYBE WITH VIRGA) MOVING ENE OVER OUR
GULF OF MEXICO WATERS. IT`S WARM AND HUMID. TEMPERATURES ARE HOLDING
IN THE MID 70S...DEWPOINTS ARE IN THE LOWER 70S.
.FORECAST...
EVEN THOUGH SHOWERS HAVE WANED AROUND THE REGION...I DON`T PLAN TO
UPDATE PUBLIC ZONES. THE EVENING SOUNDING WAS MOIST...AND STABILITY
INDEX VALUES INCLUDED SOME RELATIVELY UNSTABLE NUMBERS...K INDEX =
31 AND LIFTED INDEX = MINUS 4. I GUESS MINOR BOUNDARIES ARE STILL
CAPABLE OF INITIATION SOME NEW SHOWERS...SO I WILL LEAVE ONGOING 30
PCT POPS INTACT.
&&
.MARINE...
THE WEAK SURFACE RIDGE AXIS IS EXPECTED TO SHIFT SOUTH OVER THE KEYS
DURING THE NIGHT...SO SURFACE WINDS SHOULD GO CLOSE TO SOUTH OVER
THE AREA...MORE LIKE SSW OVER GULF AND FLORIDA BAY WATERS.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL ALONG THE KMIA-KEYW TWEB ROUTE AND AT
THE ISLAND TERMINALS OVERNIGHT. SEVERAL LAYERS OF CLOUDS WILL AFFECT
THE ROUTE...WITH AREAS OF CEILINGS AROUND FL060-FL100 AND PREVAILING
CEILINGS BETWEEN FL150 AND FL200. POCKETS OF MIST WILL PRODUCE LOCAL
MVFR VISIBILITIES OVER THE EVERGLADES IN THE EARLY MORNING HOURS.
SURFACE WINDS AT KEYW AND KMTH WILL BE LIGHT AND
VARIABLE...PRIMARILY SOUTHEAST AT 6 KT OR LESS.
.THIS DATE IN WEATHER HISTORY...
ON FEBRUARY 26 1935 ROBERT WATSON-WATT PERFORMED THE FIRST
SUCCESSFUL DEMONSTRATION OF HIS AIRCRAFT REMOTE DETECTION SYSTEM
(USING RADIO WAVES) NEAR DAVENTRY IN THE UNITED KINGDOM. HE WENT ON
TO FURTHER DEVELOP THIS SYSTEM AND ON APRIL 2 OF THAT YEAR WAS
GRANTED A PATENT FOR "RADAR". THE ENORMOUS VALUE OF AIRCRAFT RADAR
IN THE FOLLOWING WORLD WAR WOULD LEAD TO ITS LATER ADAPTATION FOR
WEATHER DETECTION...EVENTUALLY EVOLVING INTO THE DOPPLER RADAR
SYSTEMS USED BY THE NATIONAL WEATHER SERVICE TODAY.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...NONE.
$$
PUBLIC/MARINE..........BROCK
AVIATION/SHORT TERM....LEE
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1200 PM CST MON FEB 26 2007
.DISCUSSION...
313 AM CST
THE 1500 METER AGL WIND PLOT SHOWS THE CENTER OF THE CIRCULATION
OVER EASTERN WISCONSIN BETWEEN SHEBOYGAN AND MILWAUKEE. THE SURFACE
LOW WAS OVER MILWAUKEE AT 08 UTC. THE ACARS SOUNDING AT ORD AT 0601
UTC SHOWS SOME VEERING BELOW 1.2 KILOMETERS. THERE IS STILL SOME
WARM AIR ADVECTION IN THE LOWEST LAYER OF THE ATMOSPHERE. THERE IS
SOME AREAS OF LIGHT PATCHY FOG IN THE MORNING. WATER VAPOR LOOP
SHOWS THIS CIRCULATION HAS BEEN DRIFTING NORTH. THIS CIRCULATION OR
UPPER AIR LOW IS FORECAST TO MOVE NORTH AND JOIN THE CIRCULATION OF
A 500 MB LOW CENTERED OVER NEWFOUNDLAND. THAT WILL OCCUR THURSDAY
NIGHT. THE SURFACE LOW WILL MOVE INTO MICHIGAN AND SLOWLY DISSIPATE.
BY MONDAY EVENING THE LOW LEVEL WIND FROM THE SURFACE TO 1.2
KILOMETER ARE EXPECTED TO BECOME WESTERLY. THIS IS SEEN ON THE LOCAL
WRF ARW MODEL FORECAST. THE TEMPERATURE DEWPOINT SPREAD IS EXPECTED
TO REMAIN VERY LOW THROUGH THIS EVENING. WE EXPECT THE SKY TO BE
OVERCAST WITH A CHANCE OF LIGHT SNOW SHOWERS TODAY. THERE WILL BE
SOME FOG THIS MORNING. THERE IS VERY WET SNOW AND WATER ON THE
GROUND WILL ADD TO THE LOW LEVEL MOISTURE.
A GRADUAL CLEARING OF THE SKY WILL TAKE PLACE TUESDAY AND TUESDAY
NIGHT. A HIGH MOVES INTO THE REGION. BOTH THE GFS AND WRF BRING A
500 MB RIDGE INTO ILLINOIS BY EARLY WEDNESDAY MORNING. ON THURSDAY
A TROUGH MOVES INTO THE GREAT PLAINS WITH A SURFACE CYCLONE IN
WESTERN MISSOURI. THE HIGH TEMPERATURE ON THURSDAY IS EXPECTED TO
CLIMB INTO THE MIDDLE 40S. THERE WILL BE RAIN ON THURSDAY AS THE
CYCLONE MOVES INTO IOWA. THIS CYCLONE WILL MOVE INTO WISCONSIN
BY FRIDAY MORNING. THE CURRENT FORECAST REFLECTS THIS SYNOPTIC TREND
THROUGH THE WEEK. ONLY MADE SOME MINOR ADJUSTMENTS ON THE
TEMPERATURE FORECAST AND WEATHER FORECAST.
&&
.AVIATION DISCUSSION REGARDING 18Z TAFS...
1200 PM CST
SLUGGISH LO PRES AREA OVR SRN LK MI WILL DRIFT SLOWLY EWD THRU
PERIOD. WRAP ARND STRATUS/STRATO CU DECK HAS LIFTED INTO LOW MVFR
RANGE. EXPECT THAT THIS WILL RMN GENLY UNCHANGED THROUGH TNGT AS
RGN RMNS IN RATHER TIGHT CYCLONIC TURNING AND MEAN RH CROSS SECTIONS
SUGGEST MOIST LY WILL RMN TRAPPED BY INVERSION ALF AND WEAK LLVL
FLOW. SATLT LOOPS DO SHOW LARGE AREA OF CLRG OVR IA BUT THIS SHOULD
WORK ESEWD TO S OF TERMINALS. WILL IMPROVE CIGS TO VFR TUE MRNG AS
UPR LO PULLS AWAY AND SOME DIURNAL IMPROVEMENT TAKES PLACE.
CURRENT RADAR LOOPS SHOW AREA OF LGT SNOW LIFTG ENEWD ACRS EXTRM NRN
IL. THIS TREND WILL CONT THIS AFTN SO WILL JUST HAVE SOME MVFR VIS
TO START OUT THIS AFTN. SATLT LOOPS ALSO CONFIRM A WEAK UPR LVL
DSTBC SHEARING EWD ACRS SRN WI THAT IS RESPONSIBLE FOR THE INCREASED
SNO COVG. OVCE THIS PASSES THRU THREAT OF ANY RESTRICTIONS DUE TO
VIS SHOULD END.
WINDS WILL RMN WLY-WNWLY THRU PERIOD. SPEED IN 10-15 KT RANGE THIS
AFTN TO DMNSH TO BLO 10 KTS BY SS.
MERZLOCK
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...NONE.
.IN...NONE.
.LM...NONE.
&&
$$
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.
&&
$$
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 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 MARQUETTE MI
1022 PM EST MON FEB 26 2007
.UPDATE...
HAVE ALLOWED ALL HEADLINES TO EXPIRE AS SCHEDULED THIS EVENING AS
ONLY LIGHT SNOW ACCUMULATIONS OF 1 INCH OR LESS ARE EXPECTED FOR THE
REMAINDER OF THE NIGHT. MAIN FCST CONCERN NOW IS POTENTIAL OF FZDZ.
FZDZ HAS BEEN OCCURRING IN PARTS OF NRN LWR MI...AND FZDZ WAS
OCCURRING AT KAPX WHEN THE 00Z SOUNDING WAS TAKEN. THE TEMP/MOISTURE
PROFILE ON THE SOUNDING CERTAINLY DID NOT LOOK SUPPORTIVE OF FZDZ
WITH NEAR SATURATION TO THE -14C ISOTHERM.
TAMDAR SOUNDING FROM KSAW JUST BEFORE 01Z SHOWED NEAR SATURATION TO
-17C (9.9KFT). OF COURSE...THAT DOESN`T MEAN MOISTURE WILL EXTEND TO
THAT COLD OF A LAYER ALL NIGHT. IF YOU ERODE THE TOP 2KFT OF THE
MOISTURE LAYER ON THE TAMDAR SOUNDING...THE COLDEST TEMP IN THE
MOIST LAYER WILL ONLY BE -12C. SINCE FZDZ OCCURRED AT KAPX WITH
MOISTURE TO -14C... WILL OPT TO INCLUDE PATCHY FZDZ IN FCST EVEN
THOUGH IT WOULD SEEM TO BE A LOW PROBABILITY. AS FOR TEMPS...DID
RAISE MINS SLIGHTLY BASED ON CURRENT DWPT READINGS AND EXPECTED OVC
CONDITIONS THRU THE NIGHT.
&&
.PREV DISCUSSION (ISSUED AT 340 PM EST)...
...ANOTHER SIGNIFICANT SNOWFALL POSSIBLE WED NIGHT INTO SAT...
SYNOPSIS...
12Z RAOBS/LATEST WV IMAGERY SHOW CLOSED H5 LO CENTER ACRS THE UPR
MIDWEST WITH SHRTWV ROTATING WNW ARND THIS FEATURE MOVING INTO THE
SCNTRL CWA ATTM. SHARP GRADIENT OF MSTR ACRS THE UPR GRT LKS WITH
12Z APX/GRB SDNGS SHOWING DEEP SATURATION THRU THE ENTIRE TROP WHILE
SKIES ARE CLR OVER NE LK SUP CLOSER TO NRLY STNRY HI CENTERED OVER
HUDSON BAY. BAND OF H85-7 FGEN BTWN THESE TWO DISTINCT AIRMASSES
NOTED BY THE GFS F6...AND THIS AXIS CORRESPONDS VERY NICELY TO THE
LOCATION OF THE HIER REFLECTIVITIES FM ERY-MQT-JUST N OF ONTONAGON.
UPR DVGC/DEEP LYR H85-3 QVECTOR CNVGC ASSOCIATED WITH THE SHRTWV IS
SUPPORTING GENERAL SN OVER MUCH OF THE FA TO THE S OF THE SHARPER
FGEN WITHIN THE DEEPER MSTR. OTRW...DRY AIR WRAPPING NNW ARND THE
CLOSED LO CENTER BEHIND THE SHRTWV APPEARS TO BE DIMINISHING THE SN
SOMEWHAT OVER THE FAR SCNTRL. TO THE W...A DEEP TROUGH IS DIGGING S
THROUGH THE E PACIFIC...WITH RUC ANALYSIS SHOWING A 130KT JET INTO
EUREKA CA. IN FACT...EVEN A FEW LIGHTNING STRIKES HAVE OCCURRED WITH
SHRA MOVING INLAND THERE. THIS TROUGH IS PROGGED TO BE THE FEATURE
RESPONSIBLE FOR THE NEXT SIGNIFICANT SNOWFALL LATE THIS WEEK.
SHORT TERM (TONIGHT AND TUE)...
12Z GFS/UKMET/CNDN MODELS TAKE SHRTWV NOW MOVING INTO THE SRN
COUNTIES WNW INTO NRN MN BY 00Z WED. NAM IS A BIT SLOWER...BUT WL
FOLLOW THE MAJORITY SCENARIO GIVEN STEADY MOTION TO THE W OF
THE COLDER CLD TOPS/TRACER FOR BETTER UPR DVGC ASSOCIATED WITH THE
SHRTWV. WITH PASSAGE OF SHRTWV TO THE W THIS EVNG...GFS INDICATES
H85-7 FGEN WL WEAKEN SUBSTANTIALLY BTWN 00Z-06Z AS LINGERING UPR
DVGC EXITS OVER WRN LK SUP. DESPITE DEPARTURE OF STRONGER
DYNAMICS...GFS SHOWS RELATIVELY DEEP MSTR (WELL ABV HGT OF -10C
ISOTHERM) LINGERING IN LGT CYC NE FLOW THAT ONLY SLOWLY BECOMES MORE
NEUTRAL/ACYC ON TUE UNDER SLOWLY RISING HGTS/MSLP AS HUDSON BAY HI
SLOWLY BLDS TOWARD THE UPR GRT LKS.
IN TERMS OF WX...WL EXTEND GOING HEADLINES A COUPLE OF HRS OVER ALL
BUT THE FAR SCNTRL (WHERE ARRIVAL OF DRIER AIR IS NOW IN PROGRESS)
TO ACCOUNT FOR LINGERING DYNAMICS THIS EVNG. OTRW...WL MAINTAIN HIER
POPS LONGER OVER THE NCNTRL AND W...WHERE DYNAMICS WL BE LAST TO
EXIT AND/OR LINGERING NE FLOW WL UPSLOPE. HOWEVER...WL MAINTAIN AT
LEAST CHC POPS EVERYWHERE THRU THE NGT TO ACCOUNT FOR RELATIVELY
DEEP MSTR INTO FVRBL SN GROWTH LYR WITHIN WEAKENING CYC FLOW. GIVEN
THE EXPECTED CLD COVER/NE FLOW OFF LK SUP...TENDED TOWARD THE HI END
OF MOS GUIDANCE FOR MIN TEMPS WITH THE LOWEST TEMPS OVER THE E
CLOSER TO DRIER LLVL AIR IN ONTARIO. THEN GRDLY FADING POPS ON TUE
UNDER STILL CLDY SKIES...MOST TENACIOUS POPS IN NE UPSLOPE AREAS ALG
LK SUP. GOING HI TEMPS LOOK RSNBL.
LONG TERM (TUE NIGHT THROUGH NEXT MON)...
TUE NIGHT INTO WED...MUCH OF THIS PERIOD WILL BE DOMINATED BY THE
CURRENT MID LEVEL UPPER TROUGH. AT 00Z WED...THIS TROUGH SHOULD
STRETCH FROM NORTHERN MN ACROSS NORTHERN WI AND INTO LOWER MI. ON
TUE NIGHT...HEIGHTS ARE PROGGED TO RISE IN THE SOUTHERN PORTION OF
THE WESTERN GREAT LAKES REGION AS THE CURRENT TROUGH OFF THE WEST
COAST MOVES INLAND. THIS HEIGHT RISE WILL RESULT IN THE MID-LEVEL
TROUGH MOVING SLOWLY NORTHWARD. ALTHOUGH THE ATMOSPHERE REMAINS
FAIRLY MOIST ACROSS THE CWA WITH THE TROUGH...THE LACK OF ANY
SIGNIFICANT VERTICAL MOTION PREVENTS MODELS FROM PRINTING OUT MUCH
IF ANY QPF. NONETHELESS...THINK AT LEAST A FEW FLURRIES ARE
WARRANTED. ON WED...THE MID LEVEL TROUGH SHIFTS EVEN FARTHER
NORTHWARD...WITH A MID LEVEL RIDGE AXIS PROGGED TO BUILD INTO THE
CWA. THEREFORE THE MID LEVELS WILL BE DRYING OUT...BUT THE
SUBSIDENCE ALONG WITH A ESE LOW LEVEL FLOW WILL HELP KEEP LOW LEVEL
MOISTURE/STRATUS IN. HAVE STILL MAINTAINED A FEW FLURRIES POSSIBLE
OUT OF THIS DECK...WITH EVEN A CHANCE FOR SOME LIGHT SNOW IN THE FAR
SOUTH CENTRAL WHERE EAST WINDS AND MARGINAL INSTABILITY EXISTS TO
ALLOW FOR LAKE ENHANCEMENT. AS FAR AS TEMPERATURES GO...HAVE RAISED
LOWS TUE NIGHT GIVEN PERSISTENT CLOUD COVER. HIGHS FOR WED SEEM
REASONABLE.
WED NIGHT...HEIGHT FALLS ARE PROGGED TO BEGIN ALOFT WED NIGHT AS THE
FIRST SHRTWV EJECTS OUT OF THE UPPER TROUGH TOWARDS UPPER MICHIGAN.
BY 12Z THU...THIS SHRTWV IS SHOWN OVER NORTHERN WI. 285-300K
ISENTROPIC LIFT/MID LEVEL FRONTOGENESIS OCCURRING AHEAD OF THE
SHRTWV IN CONJUNCTION WITH THE DPVA WILL SPREAD BANDS OF SNOW
NORTHWARD FROM WISCONSIN INTO THE SW U.P. WED EVENING AND ACROSS
MOST OF THE REST OF THE CWA AFTER MIDNIGHT. DRY EASTERLY FLOW MAY
HELP TO KEEP THE SNOW AT A MINIMUM TOWARDS THE EASTERN U.P. AND THUS
MAINTAINED CHANCE POPS FOR LUCE COUNTY. A FEW INCHES ARE NOT OUT OF
THE QUESTION...WITH AMOUNTS LIKELY TOUCHING ADVISORY CRITERIA...DUE
TO BOTH A COMBINATION OF LIFT INSIDE THE DENDRITIC SNOW GROWTH LAYER
AND A DEEP (10000 FT) LAYER OF AGGREGATION BELOW IT. HAVE RAISED LOW
TEMPERATURES UP DUE TO CLOUD COVER AND INCREASING EASTERLY WIND
KEEPING READINGS FROM FALLING MUCH.
THU...A MUCH STRONGER SHRTWV...CURRENTLY LOCATED AT THE BASE OF THE
TROUGH IN THE EAST PACIFIC...IS PROGGED TO BE LOCATED OVER EASTERN
KS AT 12Z THU. ASSOCIATED WITH THIS SHRTWV IS AN EXPECTED UPPER 980S
MB LOW...WHICH SHOULD BE CENTERED NEAR KANSAS CITY AT 12Z. SINCE
THIS SHRTWV WILL BE RUNNING INTO THE RIDGE THAT HAS BEEN BUILT OUT
AHEAD OF IT...THE SHRTWV (ALONG WITH THE SURFACE LOW) WILL HAVE TO
TAKE A NE TRACK AND BY 00Z IS PROGGED NEAR THE QUAD CITIES. BRIEF
RIDGING OCCURRING AHEAD OF THIS SHRTWV SHOULD PUSH THE SHRTWV OVER
NORTHERN WI LATE WED NIGHT ACROSS THE CWA IN THE MORNING. THUS AN
ADDITIONAL FEW INCHES ARE POSSIBLE. THE RIDGING WILL BE SHORT LIVED
AS BY LATE IN THE DAY...THE GFS AND ECMWF SHOW HEIGHTS FALLING AGAIN
AHEAD OF THE STRONGER SHRTWV. 285-290K ISENTROPIC LIFT OCCURRING
AHEAD OF THIS SHRTWV SHOULD SPREAD MORE SNOW BACK INTO THE CWA.
GIVEN THE TWO POSSIBLE SCENARIOS FOR SNOWFALL...HAVE RAISED POPS TO
70 PERCENT. IN ADDITION TO THE SNOWFALL...WINDS ARE PROGGED TO
INCREASE QUITE A BIT AS THE SURFACE LOW NEAR KANSAS CITY DEEPENS
INTO THE LOW 980S WHILE MOVING UP TO THE QUAD CITIES. THE 12Z GFS
NEARLY SHOWS STORM FORCE WINDS ON NORTHERN LAKE MICHIGAN WITH 50KT
AT 950MB...MEANWHILE GALE FORCE WINDS OF 40 KT OR HIGHER ARE LIKELY
ON LAKE SUPERIOR. THEREFORE GOING GALE OUTLOOK LOOKS REASONABLE.
THU NIGHT THROUGH MON...THERE ARE TWO CONCERNS FOR THIS TIME PERIOD.
THE FIRST AND MORE IMMEDIATE IS THE EVOLUTION AND TRACK OF THE
SURFACE LOW FROM THU. LOOKING AT THE 00Z AND 06Z GUIDANCE...MODELS
ARE IN GENERALLY GOOD AGREEMENT THAT A 500MB LOW WILL BE SITUATED
SOMEWHERE IN WESTERN IOWA. HOWEVER...THE SURFACE LOW LOCATION IS
MUCH MORE UNCERTAIN...WITH PLACEMENTS VARYING FROM EASTERN IOWA (06Z
GFS)...NE MISSOURI (00Z UKMET AND MOST OF THE 00Z GFS ENSEMBLES) TO
NEAR CHICAGO (00Z CANADIAN) AND NEAR GREEN BAY (00Z ECMWF).
NONETHELESS...ALL MODELS AGREE ON A PRESSURE IN THE LOW TO MID
980S...WHICH MEANS THIS WILL LIKELY BE A SIGNIFICANT STORM. SINCE
THE OVERALL TREND THE PAST FEW DAYS HAS BEEN MORE AND MORE TO THE
SE...PREFER A SOLUTION ALONG THE LINE OF THE 00Z UKMET/CANADIAN/GFS
ENSEMBLES. 12Z GUIDANCE IS VERY SIMILAR TO THE 00Z AND 06Z
GUIDANCE...THEREFORE PREFERRED SOLUTION STILL SEEMS REASONABLE. THIS
SOLUTION SUGGESTS THE SURFACE LOW WILL TRACK UP INTO CENTRAL LOWER
MICHIGAN FRI NIGHT...SPREADING MODERATE TO HEAVY SNOW IN THE
DEFORMATION ZONE INTO UPPER MICHIGAN. IF THIS SOLUTION IS
CORRECT...THERE MAY ALSO BE A POSSIBILITY FOR LAKE ENHANCEMENT TO
OCCUR FOR THE NORTH CENTRAL U.P.. WITH NE WINDS...THE HIGHER TERRAIN
WEST OF MARQUETTE COULD END UP WITH SOME VERY HEAVY SNOW. SNOW
SHOULD BEGIN TO DIMINISH ON SAT AS BOTH THE SURFACE AND MID LEVEL
LOWS PULL AWAY. THIS EVENT WILL CONTINUE TO BE HIGHLIGHTED IN THE
HWO...WHILE POPS FOR THE THU NIGHT THROUGH FRI NIGHT WILL BE RAISED
TO LIKELY. WOULD LIKE TO GO EVEN HIGHER...BUT THE RELIABLE ECMWF
MODEL REMAINS CONSISTENT ON SUGGESTING A DRY SLOT ON FRI (ONLY MODEL
THAT SHOWS THIS...THOUGH).
THE SECOND CONCERN FOR THE EXTENDED DEPENDS A LOT ON HOW QUICKLY THE
STORM EXITS THE AREA. THE CURRENT 00Z ECMWF RUN AND PREVIOUS GFS
RUNS FROM THE END OF LAST WEEK SUGGESTED THE POSSIBILITY FOR A BRIEF
SHOT OF ARCTIC AIR TO MOVE INTO THE AREA LATE SUN INTO MON. IF THE
STORM SLOWS UP ENOUGH...A BUILDING RIDGE OVER THE WESTERN U.S. WILL
ALLOW AN UPPER TROUGH AND SHRTWV OVER THE NORTHWEST TERRITORIES TO
DIVE SE TOWARDS THE GREAT LAKES. HOWEVER...IF THE STORM IS FASTER...
A PORTION OF THE WESTERN RIDGE WILL BUILD TOWARDS THE GREAT LAKES
(SEE 06Z GFS AND 00Z UKMET) AND THUS KEEP THE COLD AIR WELL UP TO
THE NORTH. FOR NOW WILL FOLLOW HPC GUIDANCE WHICH BLENDS THE TWO
OPTIONS TOGETHER...WHICH RESULTS IN SOME COLD AIR AND LAKE EFFECT
SNOWS INTO THE CWA SUN INTO MON...BUT NOT AS COLD AS SUGGESTED BY
THE ECMWF.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
ROLFSON (UPDATE)
KC (SHORT TERM)
AJ (LONG TERM)
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1004 PM EST MON FEB 26 2007
.UPDATE...WILL NOT BE ISSUING A FREEZING RAIN ADVISORY. WEATHER
HAS IN FACT CHANGED TO MAINLY A LIGHT SNOW ACROSS NORTHERN LOWER
MICHIGAN. ALSO FELT THAT RECENT SNOWFALL AND DRIFTING HAS LEFT
ENOUGH OF A COATING OF SNOW ON MOST ROADS THAT THE IMPACT OF THE
ICE BUILDUP WOULD BE MINIMAL. CALLS MADE TO AREA LAW ENFORCEMENTS
DO SUPPORT THE IDEA THAT IMPACTS ARE MINIMAL. NO ACCIDENTS
REPORTED. PERSONS OUT ON AREA ROADWAYS TONIGHT SHOULD HOWEVER
REALIZE THAT FREEZING DRIZZLE DID OCCUR AND THE ROADS ARE AT LEAST
A LITTLE MORE SLICK.
AFTER THE SNOW ENDS...THERE COULD STILL BE SOME PATCHY FREEZING
DRIZZLE. AS A MATTER OF FACT...THE LOWER ATMOSPHERE WILL REMAIN DEEP
IN MOISTURE...AND ANY SMALL SCALE FEATURE THAT ROTATES AROUND THE
FILLING LOW PRESSURE COULD SPARK OF ADDITIONAL FREEZING DRIZZLE.
NO FURTHER UPDATES TO THE FORECAST ARE PLANNED. SMD
&&
.PREV DISCUSSION... /ISSUED 907 PM EST MON FEB 26 2007/
UPDATE...SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING
THAT SFC LOW HAS MEANDERED INTO MANISTEE. AREA OF LIGHT SNOW FROM
DOWNSTATE HAS ROTATED UP NORTHWARD AND INTO NORTHERN LOWER THIS
EVENING AHEAD OF SHORTWAVE SEEN ON DARKENED AREA OF LATEST WV
IMAGERY. THIS OCCURRING IN WEAK...BUT CONFLUENT FLOW IN THE MID
LEVELS...HELPING TO SQUEEZE OUT THE PRECIPITATION. THE INITIAL BURST
OF THIS ARE OF LIGHT PRECIP HAS YIELDED A MIXTURE OF LIGHT
SNOW/LIGHT SLEET AND FREEZING DRIZZLE. ALTHOUGH FORECAST MODEL
SOUNDINGS AND ACARS DATA SUGGEST THAT THE FREEZING DRIZZLE ASPECT OF
THINGS WOULD SEEM DIFFICULT TO COME BY (NO SHEAR AT TOP OF MOIST
LAYER AND MOISTURE EXTENDING TO THE -12C ISOTHERM)...THE ACARS
SOUNDING WAS FROM DOWNSTATE WHERE IN FACT IT WAS SNOWING...AND THE
MODEL SOUNDINGS ARE LIKELY MISSING SOME DRYING ALOFT THAT OCCURRED
BETWEEN THE SNOW FROM TODAY AND THIS BATCH COMING IN.
THEREFORE...OUR ATMOSPHERE WAS LIKELY DRIED OUT ENOUGH ALOFT...AND
THE DEEPENING LOW LEVEL MOISTURE AHEAD OF THE SHORTWAVE WAS
PROVIDING THE SPARK FOR AN ONSET OF DRIZZLE. THE NORTHWARD
ADVANCEMENT OF THE SHORTWAVE WILL LIKELY TRANSLATE THE FREEZING
DRIZZLE TO MORE LIGHT SNOW AS THE EVENING WEARS ON. PROBLEM IS THAT
WE HAVE ALREADY SEEN A COATING OF ICE ON CARS HERE AT THE
OFFICE...AND ANY FURTHER ICING COULD RESULT IN THE NEED FOR A
FREEZING RAIN ADVISORY. WILL BE KEEPING CLOSE TABS ON THIS WEATHER
SCENARIO OVER THE NEXT HOUR OR SO.
HIGHER LOW LEVEL MOISTURE CONTENT WILL KEEP SKIES CLOUDY FOR ALMOST
ALL AREAS TONIGHT...AND MINIMUM TEMPERATURES UP A FEW DEGREES FROM
PREVIOUS FORECAST LOWS.
EASTERN UPPER HAS CEILINGS AROUND 6KFT...SUGGESTING THAT FREEZING
DRIZZLE IS LIKELY NOT GOING TO BE A PLAYER UP THERE. WINDS HAVE
SLACKENED MOST AREAS TOO...WITH 5 KNOTS SOUTH AND AS HIGH AS 15 KTS
NORTH. MADE APPROPRIATE ADJUSTMENTS TO MARINE AND PUBLIC FORECASTS.
SMD
PREV DISCUSSION ISSUED AT 344 PM EST MON FEB 26 2007
DISCUSSION...THE VERTICALLY STACKED LOW IS OVER CENTRAL LAKE
MICHIGAN WITH THE PRECIPITATION SLOWLY FADING INTO THE SUNSET. LAST
REMNANTS OF DEFORMATION SNOW IS ALONG LAKE HURON SHORELINE FROM THE
STRAITS TO PRESQUE ISLE LIGHT. AS THIS BAND AS CONTINUALLY MOVED
THROUGH THE DAY TOWARD THE NORTHEAST IN THE VERY NEAR TERM IT IS
EXPECTED TO CONTINUE TO MOVE OFFSHORE. OTHERWISE, LIGHT SNOW IS
ROUNDING THE BOTTOM OF THE TROUGH.
MODELS ARE IN GOOD AGREEMENT THROUGH 00Z WEDNESDAY. SO WILL BLEND
THE FORECAST.
TONIGHT...WITH THE WEAKENING SYSTEM, THE SNOW WILL CONTINUE TO
DIMINISH. SO HAVE ONLY UP TO AN INCH AS THE SFC LOW DRIFTS EAST,
ACROSS S LOWER. THE GRADIENT REMAINS SOMEWHAT TIGHT, SO THE WINDS
WILL CONTINUE ALONG THE 10 TO 20 MPH RANGE.
TUESDAY...THE SFC LOW CONTINUES TO PULL OUT OF THE REGION WITH THE
500 MB LOW BY TUESDAY EVENING BEING ONLY A WEAK TROUGH. HIGH
PRESSURE IS SLOWLY BUILDING IN, BUT WITH ALL OF THE MOISTURE STILL
LEFT OVER INTO THE LOWER LEVELS (850 MB LEVEL RH AROUND 90%) WOULD
STILL EXPECT THAT THERE WILL BE SOME CHANCE FOR SNOW OR FLURRIES.
LUTZ
LATER PERIODS...FOCUS WILL CONTINUE TO BE ON NEXT STORM SYSTEM
EJECTING OUT OF THE CENTRAL PLAINS...AND INTO THE WESTERN GREAT
LAKES REGION. TIMING OF SYSTEM...PRECIPITATION TYPE...AND
PRECIPITATION AMOUNTS WILL BE THE MAIN CONCERNS. MODELS ARE FAIRLY
SIMILAR AT THIS TIME...SO WILL GO WITH A GENERAL BLEND THROUGH
FRIDAY.
TUESDAY NIGHT AND WEDNESDAY...DEFORMATION AXIS LAID OUT EAST/WEST
ACROSS NORTHERN MICHIGAN WILL CONTINUE TO STRETCH OUT. EXPECT CLOUDS
TO LINGER THROUGH WEDNESDAY...WITH SOME FLURRIES FROM TIME TO TIME.
TEMPERATURES WILL FALL INTO THE 20S IN NORTHERN LOWER TUESDAY
NIGHT...WITH TEENS IN UPPER MICHIGAN WITH A FEW MORE BREAKS IN THE
CLOUDS. HIGHS WEDNESDAY WILL REACH INTO THE UPPER 20S TO AROUND 30.
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...NAM AND GFS SEEM TO BE IN
REASONABLE AGREEMENT WITH REGARDS TO THE FEATURES OF THE UPCOMING
STORM. THE MODELS TAKE THE SURFACE LOW INTO NORTHERN MISSOURI...THEN
NORTHEASTWARD INTO EASTERN WISCONSIN. STRONG ISENTROPIC ASCENT
(290K) SETS IN LATE WEDNESDAY NIGHT AND CONTINUES DURING THE DAY ON
THURSDAY. STRONG 850-700MB 2D FRONTOGENESIS OVERSPREADS THE REGION
DURING THIS TIME PERIOD...AND WOULD EXPECT PRECIPITATION TO BECOME
WIDESPREAD AND POTENTIALLY QUITE HEAVY THURSDAY MORNING. ONE JET
SHOOTING ACROSS THE SOUTHERN PLAINS WILL COUPLE WITH A JET ACROSS
NEW ENGLAND...TO PROVIDE DECENT UPPER LEVEL DIVERGENCE ACROSS THE
GREAT LAKES REGION. THUS...GREAT DYNAMICS ARE IN PLACE FOR RAPID
INTENSIFICATION OF THE LOW PRESSURE SYSTEM. MODEL SOUNDINGS START
OFF ALL BELOW ZERO THURSDAY MORNING AT LEAST SUGGESTING THINGS WILL
START OFF AS SNOW. HOWEVER...SURGE OF WARM AIR IN THE 850-750MB
LAYER WILL TRANSITION THINGS FROM SNOW EARLY THURSDAY MORNING...TO A
MIXTURE OF SNOW AND FREEZING RAIN BY AFTERNOON. SURFACE LAYER OF
COLD AIR WILL BE STRONG ENOUGH IN THE NORTH FOR LIQUID TO REFREEZE
AND PRODUCE SLEET. THE FREEZING RAIN/SLEET/SNOW WILL CONTINUE INTO
THURSDAY NIGHT...BUT PRECIPITATION WILL BEGIN TO CHANGE OVER TO ALL
SNOW AS COLDER AIR ARRIVES LATE THURSDAY NIGHT. THE TEMPERATURE
DIURNAL RANGE WILL BE QUITE SMALL WITH THE CLOUD COVER AND
PRECIPITATION. LOWS WILL DROP INTO THE TEENS TO LOWER 20S...WITH
HIGHS TOPPING OUT AROUND 30.
EXTENDED (FRIDAY THROUGH MONDAY)...MUCH LIKE THE SYSTEM THIS
WEEKEND...LOW WILL BEGIN TO FILL AND OCCLUDE AS IT LIFTS NORTHWARD
ACROSS EASTERN UPPER...THEN INTO ONTARIO. COLD AIR...WITH 850MB
TEMPS FALLING TO -8C...WILL SPREAD INTO NORTHERN MICHIGAN EARLY
FRIDAY MORNING...CHANGING PRECIPITATION TO ALL SNOW. WITH LOW TRACK
FAIRLY CLOSE TO THE AREA...WILL AGAIN HAVE TO KEEP AN EYE ON THE
POTENTIAL FOR A DRY SLOT TO SURGE INTO THE AREA...PRODUCING A PERIOD
OF FREEZING DRIZZLE ON FRIDAY. FOR NOW...MOISTURE SHOULD BE DEEP
ENOUGH (AT LEAST -10C ISOTHERM) TO KEEP THINGS ALL SNOW. AS THE
FILLING LOW DRIFTS EAST OVER THE WEEKEND...850MB TEMPS FALL TO
AROUND -14C...AND PRECIPITATION WILL TRANSITION TO LAKE
EFFECT/ENHANCED SNOWFALL. NORTHWEST FLOW WILL CONTINUE THROUGH
SUNDAY...BEFORE WINDS BEGIN TO BACK AHEAD OF UPPER LEVEL AND SURFACE
RIDGE.
KAS
APX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
907 PM EST MON FEB 26 2007
.UPDATE...SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING
THAT SFC LOW HAS MEANDERED INTO MANISTEE. AREA OF LIGHT SNOW FROM
DOWNSTATE HAS ROTATED UP NORTHWARD AND INTO NORTHERN LOWER THIS
EVENING AHEAD OF SHORTWAVE SEEN ON DARKENED AREA OF LATEST WV
IMAGERY. THIS OCCURRING IN WEAK...BUT CONFLUENT FLOW IN THE MID
LEVELS...HELPING TO SQUEEZE OUT THE PRECIPITATION. THE INITIAL BURST
OF THIS ARE OF LIGHT PRECIP HAS YIELDED A MIXTURE OF LIGHT
SNOW/LIGHT SLEET AND FREEZING DRIZZLE. ALTHOUGH FORECAST MODEL
SOUNDINGS AND ACARS DATA SUGGEST THAT THE FREEZING DRIZZLE ASPECT OF
THINGS WOULD SEEM DIFFICULT TO COME BY (NO SHEAR AT TOP OF MOIST
LAYER AND MOISTURE EXTENDING TO THE -12C ISOTHERM)...THE ACARS
SOUNDING WAS FROM DOWNSTATE WHERE IN FACT IT WAS SNOWING...AND THE
MODEL SOUNDINGS ARE LIKELY MISSING SOME DRYING ALOFT THAT OCCURRED
BETWEEN THE SNOW FROM TODAY AND THIS BATCH COMING IN.
THEREFORE...OUR ATMOSPHERE WAS LIKELY DRIED OUT ENOUGH ALOFT...AND
THE DEEPENING LOW LEVEL MOISTURE AHEAD OF THE SHORTWAVE WAS
PROVIDING THE SPARK FOR AN ONSET OF DRIZZLE. THE NORTHWARD
ADVANCEMENT OF THE SHORTWAVE WILL LIKELY TRANSLATE THE FREEZING
DRIZZLE TO MORE LIGHT SNOW AS THE EVENING WEARS ON. PROBLEM IS THAT
WE HAVE ALREADY SEEN A COATING OF ICE ON CARS HERE AT THE
OFFICE...AND ANY FURTHER ICING COULD RESULT IN THE NEED FOR A
FREEZING RAIN ADVISORY. WILL BE KEEPING CLOSE TABS ON THIS WEATHER
SCENARIO OVER THE NEXT HOUR OR SO.
HIGHER LOW LEVEL MOISTURE CONTENT WILL KEEP SKIES CLOUDY FOR ALMOST
ALL AREAS TONIGHT...AND MINIMUM TEMPERATURES UP A FEW DEGREES FROM
PREVIOUS FORECAST LOWS.
EASTERN UPPER HAS CEILINGS AROUND 6KFT...SUGGESTING THAT FREEZING
DRIZZLE IS LIKELY NOT GOING TO BE A PLAYER UP THERE. WINDS HAVE
SLACKENED MOST AREAS TOO...WITH 5 KNOTS SOUTH AND AS HIGH AS 15 KTS
NORTH. MADE APPROPRIATE ADJUSTMENTS TO MARINE AND PUBLIC FORECASTS.
SMD
.PRE DISCUSSION ISSUED AT 344 PM EST MON FEB 26 2007
DISCUSSION...THE VERTICALLY STACKED LOW IS OVER CENTRAL LAKE
MICHIGAN WITH THE PRECIPITATION SLOWLY FADING INTO THE SUNSET. LAST
REMNANTS OF DEFORMATION SNOW IS ALONG LAKE HURON SHORELINE FROM THE
STRAITS TO PRESQUE ISLE LIGHT. AS THIS BAND AS CONTINUALLY MOVED
THROUGH THE DAY TOWARD THE NORTHEAST IN THE VERY NEAR TERM IT IS
EXPECTED TO CONTINUE TO MOVE OFFSHORE. OTHERWISE, LIGHT SNOW IS
ROUNDING THE BOTTOM OF THE TROUGH.
MODELS ARE IN GOOD AGREEMENT THROUGH 00Z WEDNESDAY. SO WILL BLEND
THE FORECAST.
TONIGHT...WITH THE WEAKENING SYSTEM, THE SNOW WILL CONTINUE TO
DIMINISH. SO HAVE ONLY UP TO AN INCH AS THE SFC LOW DRIFTS EAST,
ACROSS S LOWER. THE GRADIENT REMAINS SOMEWHAT TIGHT, SO THE WINDS
WILL CONTINUE ALONG THE 10 TO 20 MPH RANGE.
TUESDAY...THE SFC LOW CONTINUES TO PULL OUT OF THE REGION WITH THE
500 MB LOW BY TUESDAY EVENING BEING ONLY A WEAK TROUGH. HIGH
PRESSURE IS SLOWLY BUILDING IN, BUT WITH ALL OF THE MOISTURE STILL
LEFT OVER INTO THE LOWER LEVELS (850 MB LEVEL RH AROUND 90%) WOULD
STILL EXPECT THAT THERE WILL BE SOME CHANCE FOR SNOW OR FLURRIES.
LUTZ
LATER PERIODS...FOCUS WILL CONTINUE TO BE ON NEXT STORM SYSTEM
EJECTING OUT OF THE CENTRAL PLAINS...AND INTO THE WESTERN GREAT
LAKES REGION. TIMING OF SYSTEM...PRECIPITATION TYPE...AND
PRECIPITATION AMOUNTS WILL BE THE MAIN CONCERNS. MODELS ARE FAIRLY
SIMILAR AT THIS TIME...SO WILL GO WITH A GENERAL BLEND THROUGH
FRIDAY.
TUESDAY NIGHT AND WEDNESDAY...DEFORMATION AXIS LAID OUT EAST/WEST
ACROSS NORTHERN MICHIGAN WILL CONTINUE TO STRETCH OUT. EXPECT CLOUDS
TO LINGER THROUGH WEDNESDAY...WITH SOME FLURRIES FROM TIME TO TIME.
TEMPERATURES WILL FALL INTO THE 20S IN NORTHERN LOWER TUESDAY
NIGHT...WITH TEENS IN UPPER MICHIGAN WITH A FEW MORE BREAKS IN THE
CLOUDS. HIGHS WEDNESDAY WILL REACH INTO THE UPPER 20S TO AROUND 30.
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...NAM AND GFS SEEM TO BE IN
REASONABLE AGREEMENT WITH REGARDS TO THE FEATURES OF THE UPCOMING
STORM. THE MODELS TAKE THE SURFACE LOW INTO NORTHERN MISSOURI...THEN
NORTHEASTWARD INTO EASTERN WISCONSIN. STRONG ISENTROPIC ASCENT
(290K) SETS IN LATE WEDNESDAY NIGHT AND CONTINUES DURING THE DAY ON
THURSDAY. STRONG 850-700MB 2D FRONTOGENESIS OVERSPREADS THE REGION
DURING THIS TIME PERIOD...AND WOULD EXPECT PRECIPITATION TO BECOME
WIDESPREAD AND POTENTIALLY QUITE HEAVY THURSDAY MORNING. ONE JET
SHOOTING ACROSS THE SOUTHERN PLAINS WILL COUPLE WITH A JET ACROSS
NEW ENGLAND...TO PROVIDE DECENT UPPER LEVEL DIVERGENCE ACROSS THE
GREAT LAKES REGION. THUS...GREAT DYNAMICS ARE IN PLACE FOR RAPID
INTENSIFICATION OF THE LOW PRESSURE SYSTEM. MODEL SOUNDINGS START
OFF ALL BELOW ZERO THURSDAY MORNING AT LEAST SUGGESTING THINGS WILL
START OFF AS SNOW. HOWEVER...SURGE OF WARM AIR IN THE 850-750MB
LAYER WILL TRANSITION THINGS FROM SNOW EARLY THURSDAY MORNING...TO A
MIXTURE OF SNOW AND FREEZING RAIN BY AFTERNOON. SURFACE LAYER OF
COLD AIR WILL BE STRONG ENOUGH IN THE NORTH FOR LIQUID TO REFREEZE
AND PRODUCE SLEET. THE FREEZING RAIN/SLEET/SNOW WILL CONTINUE INTO
THURSDAY NIGHT...BUT PRECIPITATION WILL BEGIN TO CHANGE OVER TO ALL
SNOW AS COLDER AIR ARRIVES LATE THURSDAY NIGHT. THE TEMPERATURE
DIURNAL RANGE WILL BE QUITE SMALL WITH THE CLOUD COVER AND
PRECIPITATION. LOWS WILL DROP INTO THE TEENS TO LOWER 20S...WITH
HIGHS TOPPING OUT AROUND 30.
EXTENDED (FRIDAY THROUGH MONDAY)...MUCH LIKE THE SYSTEM THIS
WEEKEND...LOW WILL BEGIN TO FILL AND OCCLUDE AS IT LIFTS NORTHWARD
ACROSS EASTERN UPPER...THEN INTO ONTARIO. COLD AIR...WITH 850MB
TEMPS FALLING TO -8C...WILL SPREAD INTO NORTHERN MICHIGAN EARLY
FRIDAY MORNING...CHANGING PRECIPITATION TO ALL SNOW. WITH LOW TRACK
FAIRLY CLOSE TO THE AREA...WILL AGAIN HAVE TO KEEP AN EYE ON THE
POTENTIAL FOR A DRY SLOT TO SURGE INTO THE AREA...PRODUCING A PERIOD
OF FREEZING DRIZZLE ON FRIDAY. FOR NOW...MOISTURE SHOULD BE DEEP
ENOUGH (AT LEAST -10C ISOTHERM) TO KEEP THINGS ALL SNOW. AS THE
FILLING LOW DRIFTS EAST OVER THE WEEKEND...850MB TEMPS FALL TO
AROUND -14C...AND PRECIPITATION WILL TRANSITION TO LAKE
EFFECT/ENHANCED SNOWFALL. NORTHWEST FLOW WILL CONTINUE THROUGH
SUNDAY...BEFORE WINDS BEGIN TO BACK AHEAD OF UPPER LEVEL AND SURFACE
RIDGE.
KAS
&&
.APX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
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
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