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

.AVIATION (00Z TAFS)... SFC LOW CENTERED SOUTH OF STL...WITH BACK EDGE OF MORE SIGNIFICANT PRECIP NOW MOVING EASTWARD ACROSS I-65 AS OF 23Z. EXPECT THAT CIGS/VSBYS COULD DROP INTO THE UPPER-ENDS OF IFR THROUGH 2Z AT SDF/LEX TAF SITES WITH A MIXTURE OF -SN/-FZRA/-PL POSSIBLE GIVEN CURRENT AND FCST THERMAL PROFILES. HAVE FOLLOWED LATEST RUC FOR THE FIRST 6-12 HOURS OF THE TAFS...WHICH SWINGS WINDS AROUND TO THE SW THIS EVENING WITH A PERIOD OF JUST VFR CIGS AT ALL THREE TAF SITES. INTO THE POST-MIDNIGHT HOURS...SFC LOW FCST TO TRACK EAST THROUGH THE CWA WHICH WILL TURN SFC WINDS AROUND TO THE NW AND BRING A DECK OF LOWER STRATOCU WITH IT. CIGS MAY DROP BELOW 2KFT THROUGH DAYBREAK WEDNESDAY. COULD HAVE SOME SPOTS OF -FZDZ OVERNIGHT IF CIGS GET LOW ENOUGH...SOMETHING TO WATCH.

CS

&&

.MESO UPDATE/515 PM EST... WARM AIR ALOFT HAS PROGRESSED FURTHER NORTH THAN EARLIER ANTICIPATED LEADING TO NUMEROUS REPORTS OF SLEET AND EVEN SOME FREEZING RAIN NEAR SRN INDIANA AND LOU METRO OVER INTO THE FFT/LEX AREAS. ACARS SOUNDINGS AT SDF SHOW THIS WARM LAYER...WHICH WAS UNDERPLAYED BY EVEN RECENT RUNS OF THE NAM. RUC HAS A SLIGHTLY BETTER HANDLE ON IT. WILL BE SWITCHING THE SNOW ADVISORY TO A WINTER WEATHER ADVISORY TO ACCOUNT FOR THIS MIXED PRECIPITATION. PRECIP MAY CHANGE BACK TO ALL SNOW THIS EVENING AS AIR ALOFT COOLS. WE WILL LEAVE THE HEAVY SNOW WARNING ALONE FOR THE TIME BEING...AND SEE HOW THINGS EVOLVE OVER THE NEXT HOUR OR SO.

CS/MBS

&&

.SHORT TERM (TONIGHT AND WEDNESDAY)...

COMPLICATED FORECAST IN THE NEAR TERM AS TO DETERMINE WHERE SNOW ACCUMULATION GRADIENT WILL FALL. LOOKING OVER THE PAST FEW MODEL RUNS...IT APPEARS THAT THE NAM-WRF SOLUTION HAS BEEN A BIT MORE CORRECT WITH THE OVERALL PLACEMENT WITH THE HEAVIEST SNOW BAND. THE GFS IS PARTIALLY CORRECT TOO...BUT HAS BEEN OVERDOING SOME OF THE PRECIPITATION AMOUNTS IN ITS SOLUTIONS. THE 12Z STILL HAVE SOME DISAGREEMENT WITH THE PLACEMENT OF THE HEAVIEST SNOW BAND. WITH THE WRF SOLUTION BEING JUST NORTH OF THE FA...WHILE THE GFS IS A BIT MORE SOUTH. SFC LOW OVER CENTRAL MISSOURI IS FCST TO DROP INTO WESTERN KY THIS EVENING AND THEN HEAD EAST. THE GFS SHOWS AN ENHANCEMENT OF QPF OVER THE NE PORTION OF THE FA THIS EVENING AND OVER IN EASTERN KY OVERNIGHT AS UPSLOPE FORCING HELPS MAINTAIN SNOW AND SNOW SHOWERS. HAVE CHOSEN TO GO WITH A NAM-WRF COMPROMISE WHICH WILL RESULT IN CHANGES TO THE ONGOING FCST.

FIRST...THE HEAVY SNOW WARNING STILL LOOKS GOOD FOR OUR NORTHEASTERN COUNTIES. A TOTAL OF THREE TO SIX INCHES STILL WILL BE POSSIBLE IN THIS AREA. HOWEVER THE BEST CHANCES OF SEEING THOSE HIGHER ACCUMULATIONS WILL BE ACROSS NORTH OF A FRANKFORT TO PARIS LINE. ITS A REAL TOUGH CALL IN THE LEXINGTON METRO AREA AS THE NORTHERN PORTION OF THE COUNTY HAS RECEIVED A DECENT AMOUNT OF SNOW...WHILE THE SOUTHERN PART OF THE COUNTY HAS NOT. THIS IS ALSO THE CASE IN LOUISVILLE WHERE WE HAVE DUSTING HERE...BUT JUST OUTSIDE THE COUNTY WE HAVE 1/2 TO 1 INCH REPORTS ACROSS OLDHAM COUNTY.

A SHARP GRADIENT OF SNOW ACCUMULATION IS LIKELY AND PORTIONS OF THE COUNTIES IN THE WARNING AREA MAY HIT THE CRITERIA...WHILE OTHER PORTIONS DO NOT. FURTHER SOUTH AND WEST...WE PLAN ON TRIMMING BACK THE SNOW ADVISORY. PLAN ON RUNNING THIS FROM WASHINGTON COUNTY INDIANA THROUGH LOUISVILLE METRO AND DOWN TO GARRARD COUNTY. IN THIS AREA...A GENERAL 1 TO 3 INCHES OF ACCUMULATION WILL BE POSSIBLE. UPSTREAM RADAR SHOWS ANOTHER BATCH OF SNOW SHOWERS COMING INTO OUR NORTHWEST PORTIONS WHICH WILL HIT THIS ADVISORY AREA LATER THIS EVENING. ACROSS THE SOUTHWEST...MAINLY DRY CONDITIONS ARE EXPECTED TONIGHT. IN THE FAR SOUTHEAST...SOME PRECIPITATION MAY LINGER DOWN CLOSE THE SOMERSET AREA WHERE P-TYPE WILL BE A MIX OF RAIN/FZRA/PL/SNOW. AM NOT CONFIDENT ON AMOUNTS OR COVERAGE...BUT WILL KEEP A CHC IN. ACCUMULATIONS IN THIS AREA WOULD BE LITTLE OR NONE.

SNOW WILL EXIT THE REGION LATER TONIGHT FROM NORTHWEST TO SOUTHEAST...SO WILL LEAVE CURRENT ADVISORY/WARNING ENDING TIMES AS IS AND LET FUTURE SHIFTS TRIM BACK AS NECESSARY. TEMPERATURES IN THE SNOW COVERED AREAS WILL DROP OFF INTO THE TEENS LATER TONIGHT WITH LOWER TO MID 20S DOWN ACROSS THE SOUTH. MOSTLY CLOUDY SKIES WILL START OFF THE DAY ON WEDNESDAY WITH SOME CLEARING NOTED IN THE AFTERNOON. NORTH WINDS WILL KEEP TEMPERATURES BELOW NORMAL ONCE AGAIN...ESPECIALLY IN AREAS THAT HAVE SNOW PACK. IN GENERAL HAVE GONE CLOSER TO 2M RAW MODEL OUTPUT FOR THIS FORECAST PERIOD.

THANKS TO JKL/IND/PAH AND LEX MEDIA FOR COORDINATION THIS AFTERNOON.

-MJ

.LONG TERM (WEDNESDAY NIGHT THROUGH TUESDAY)...

THE VERY COLD ARCTIC AIR MASS HAS SHIFTED OFF TO THE NORTHEAST...BUT SYSTEMS ROTATING SOUTHEAST ACROSS THE NORTH CENTRAL U.S. AROUND THE COLD VORTEX OVER EAST CENTRAL CANADA WILL KEEP SOME COLD ARCTIC AIR FLOWING ACROSS THE REGION DURING THE NEXT FEW DAYS...BUT THIS AIR IS RELATIVELY DRY SO NO REALLY GOOD PRECIPITATION CHANCES FOR THE NEXT FEW DAYS. MAX AND MIN TEMPS SHOULD AVERAGE SOME 10 TO 15 DEG BELOW THE SEASONAL NORMALS FOR THIS TIME OF YEAR.

BY THE WEEKEND AND INTO THE NEXT WORKWEEK A SERIES OF PACIFIC TROUGHS OFF THE WEST COAST OF THE U.S. WILL EVENTUALLY ESTABLISH MORE OF A SPLIT FLOW PATTERN. THIS NEW SOUTHERN STREAM WILL LIKELY SET UP EAST TO WEST ACROSS THE SOUTH CENTRAL U.S. GIVEN THAT THE THE COLD AIR WILL STILL BE IN PLACE ACROSS THE REGION DUE TO THE NORTHERN STREAM...THIS SCENARIO COULD EVENTUALLY EVOLVE INTO ONE OR MORE RAIN/SNOW PRODUCING STORM SYSTEMS LATE IN THE PERIOD AND BEYOND.

ONE SUCH STORM SYSTEM IS FORECAST BY THE GFS AND THE LATEST HPC EXTENDED GUIDANCE PICKS UP ON THIS TOO. THIS LOOKS OK TO US TOO. WE WILL INTRODUCE A CHANCE OF LIGHT SNOW ON MONDAY NIGHT AND A CHANCE FOR A RAIN OR SNOW MIX ON TUESDAY. --21

&&

.LMK WATCHES/WARNINGS/ADVISORIES...

KY...HEAVY SNOW WARNING UNTIL 4 AM EST WEDNESDAY FOR KYZ032-033-035>037-040>043-048-049.

WINTER WEATHER ADVISORY UNTIL 4 AM EST WED FOR KYZ030-031- 034-038-039-047-056-057.

IN...HEAVY SNOW WARNING UNTIL 4 AM EST WEDNESDAY FOR INZ078-079. SNOW ADVISORY UNTIL 4 AM EST WEDNESDAY FOR INZ077-091-092. &&

$$

.SHORT TERM... ANOTHER COLD NIGHT IN STORE...AS CLOUDS FROM LAKE MICHIGAN HAVE STRUGGLED TO ADVANCE EASTWARD...EVEN WITH THE DIURNAL ENHANCEMENT HELPING TO RAISE INVERSION HEIGHTS UP TOWARD 4000 FEET PER DTW TAMDAR DATA. THE GOOD NEWS IS THE SUNSHINE HAS HELPED BOOST MAX TEMPS TO AROUND 10 DEGREES THIS AFTERNOON...A GOOD 3-5 DEGREES WARMER COMPARED TO YESTERDAY.

PRESSURE GRADIENT OVER SOUTHERN LOWER MICHIGAN TONIGHT LOOKS TO BE ABOUT 2 MB LESS WHEN COMPARED TO THIS MORNING. THIS SHOULD TRANSLATE TO LOWS AT OR BELOW ZERO EVERYWHERE...AND HAVE UNDERCUT GFS MOS GUIDANCE BY A GOOD 5 DEGREES IN MOST SPOTS. A FAR AS WIND CHILLS GO...WITH THE WEAKER GRADIENT...WINDS LOOK TO BE BORDERLINE...AROUND 10 MPH...WITH WIND CHILLS HOVERING RIGHT AROUND -20 F (ADVISORY CRITERIA). WILL HOLD OFF ON THE ADVISORY...AS WIND CHILLS OF -20 F OR COLDER ARE NOT EXPECTED TO BE WIDESPREAD...NOR ARE THEY EXPECTED FOR AN EXTENDED PERIOD OF TIME.

DRY AIRMASS CONTINUES TO LIMIT LAKE EFFECT ACTIVITY...AND SEE NO SIGNIFICANT CHANGES INTO TONIGHT. THE WESTERN CLOUD EDGE/CONDENSATION OVER LAKE MICHIGAN HAS ACTUALLY BEEN PULLING EAST THIS AFTERNOON.

TOMORROW LOOKS TO BE A DIFFERENT STORY...AS UPPER WAVE CURRENTLY OVER NORTHERN ALBERTA QUICKLY DIVES SOUTHEAST...TRACKING ALONG THE SOUTHERN MICHIGAN BORDER...PER NAM/GFS TROPOPAUSE PRESSURE FIELDS. THIS SHOULD AT LEAST ALLOW FOR AN ENHANCEMENT TO THE I-94/M-59 CONVERGENT BAND. HOWEVER...MODELS IMPLYING MOST/ALL OF THE SYNOPTIC SNOW WILL STAY SOUTH OF THE BORDER AS MAIN 850-700 MB THETA GRADIENT REMAINS CONFINED TO THE SOUTHERN OHIO VALLEY...WITH LITTLE IN THE WAY OF MOISTURE TRANSPORT INTO SOUTHERN LOWER MICHIGAN. STILL A LITTLE LEARY THE UPPER WAVE MAY BE DRAWN A LITTLE FARTHER NORTH THAN INDICATED...AND WILL CARRY A 50 POP FOR M-59 AND POINTS SOUTH. NO CHANGES TO MAXES TOMORROW...LOWER TEENS EXPECTED.

&&

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY

VERY LITTLE CHANGE IN THE ONGOING PATTERN THROUGH THE WEEKEND AS SEVERAL STRONG SHORTWAVES DIG INTO THE EASTERN NORTH AMERICAN UPPER TROUGH AND KEEP THE EASTERN CANADIAN POLAR VORTEX WELL-ESTABLISHED. THIS WILL MAINTAIN A COLD AIRMASS ACROSS THE REGION WITH HIGHS ONLY IN THE TEENS/LOWER 20S AND LOWS IN THE SINGLE DIGITS TO OCCASIONALLY BELOW ZERO.

THE FIRST OF THESE SHORTWAVES WILL BE PASSING SOUTH OF THE REGION TUESDAY EVENING. THERE MAY BE SOME LEFTOVER LIGHT SNOW OVER THE FAR SOUTHERN CWA FROM THIS SYSTEM (OR AT LEAST AN ENHANCEMENT TO LAKE EFFECT SNOW SHOWERS FROM THE MOISTURE IT WILL BRING)...BUT OVERALL IT WILL JUST ENSURE THAT THE STATUS QUO HOLDS...AND WE REMAIN IN THE SAME TEMPERATURE REGIME. THE NEXT SHORTWAVE WILL DROP DOWN FROM THE ARCTIC CIRCLE AND SPIN AROUND THE POLAR VORTEX. SO...EXPECT THIS FEATURE TO BRING A RESURGENCE OF COLDER AIR BY LATE FRIDAY INTO SATURDAY. ATTM...IT APPEARS THIS AIRMASS IS SOME 5-7 DEGREES C MILDER THAN THE ARCTIC AIRMASS OF THIS PAST WEEKEND...SO DO NOT EXPECT TEMPERATURES TO STRUGGLE QUITE AS MUCH.

THE FORECAST FOR SNOW SHOWERS REMAINS TRICKY...AT LEAST IN TRYING TO PICK OUT THE DAY(S) THAT HAVE THE BEST CHANCE OF LIGHT ACCUMULATION. NO LARGE STORM SYSTEMS ARE ON THE WAY...AND ANY ACCUMULATING SNOWS WILL MAINLY BE LAKE EFFECT/ENHANCED SNOW SHOWERS. AFTER A PERIOD OF ENHANCED SNOW SHOWER ACTIVITY TO START THE LONG TERM FORECAST...THE GENERAL FORECAST WILL BE FOR PERIODIC FLURRIES IN THE WEDNESDAY AND THURSDAY TIMEFRAME...WITH MORE WIDESPREAD SNOW SHOWERS BY FRIDAY AND SATURDAY AS THE AFOREMENTIONED ARCTIC SHORTWAVE DIVES THROUGH THE GREAT LAKES.

AT THE VERY END OF THE FORECAST...THE AMPLIFIED PATTERN CONTINUES TO SHOW SOME SIGNS OF RELAXING...WHICH WOULD ALLOW MORE INTRUSION OF PACIFIC AIR INTO THE REGION...AND LESS INTRUSION OF THE COLDEST AIR FROM THE ARCTIC. WILL MAINTAIN THE SLIGHT MODERATION IN THE SUNDAY TO MONDAY TIMEFRAME GIVEN SOME CONSISTENCY IN GFS RUNS DURING THE PAST FEW DAYS FOR THIS BASIC SCENARIO. STILL...TEMPERATURES SHOULD REMAIN LARGELY BELOW NORMAL.

&&

.PREV DISCUSSION...ISSUED 1210 PM EST MON FEB 5 2007

AVIATION...

BOUNDARY LAYER/INVERSION HEIGHTS ARE RISING THIS AFTERNOON...WHICH SHOULD ALLOW MVFR CEILINGS COMING OFF LAKE MICHIGAN TO FILTER INTO SOUTHEAST MICHIGAN...ESPECIALLY OVER THE DETROIT TAFS...WHERE I-94 CONVERGENT BAND LOOKS TO PERSIST. INVERSION HEIGHTS EXPECTED TO REMAIN AT OR ABOVE 4000 FEET TONIGHT AND TOMORROW MORNING. HOWEVER...LOSS OF DIURNAL COMPONENT STILL MAKES IT A TOUGH CALL WHETHER OR NOT TO CONTINUE MVFR CEILINGS AND SCATTERED SNOW SHOWERS/FLURRIES TONIGHT. WITH THE WESTERLY FLOW AND BASED ON THE 925 MB OMEGA FIELDS...WILL CARRY THE MVFR CEILINGS AND SNOW SHOWERS LONGEST OVER THE DETROIT TAF SITES.

&&

.DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...GALE WARNING...NORTH HALF UNTIL 1 PM TUESDAY

GALE WARNING...SOUTH HALF UNTIL 7 AM TUESDAY.

SMALL CRAFT ADVISORY...LHZ441-LHZ442 UNTIL 7 PM WEDNESDAY.

SMALL CRAFT ADVISORY...LHZ421-LHZ443 UNTIL 7 AM TUESDAY.

SMALL CRAFT ADVISORY FOR WINDS...LHZ422 UNTIL 7 AM TUESDAY.

LAKE ST CLAIR...SMALL CRAFT ADVISORY FOR WINDS...LCZ460 UNTIL 7 AM TUESDAY.

MI WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FOR WINDS...UNTIL 7 AM TUESDAY.

&&

$$

SHORT TERM...SF LONG TERM....DG AVIATION.....SF

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

.SYNOPSIS...LIGHT FLOW WITH PLENTY OF MOISTURE AT THE LOWER LEVELS COMBINING TO CREATE FOGGY CONDITIONS OVER THE AREA THROUGH THIS AFTERNOON. CONDITIONS WILL IMPROVE BRIEFLY BUT MORE FOG IS EXPECTED TO FORM OVERNIGHT INTO TUESDAY MORNING. AN APPROACHING LOW PRESSURE SYSTEM WILL BRING A CHANCE OF RAIN TO SOUTHWEST WASHINGTON TUESDAY AFTERNOON AND THE REST OF THE AREA TUESDAY NIGHT. ANTICIPATE WET WEATHER ON WEDNESDAY. &&

.SHORT TERM...FIRST VISIBLE SATELLITE IMAGES THIS MORNING SHOW FOG/STRATUS NEAR THE SOUND...DOWN THE I-5 CORRIDOR AND ALONG THE COAST. QUESTION FOR TODAY IS HOW LONG THE FOG WILL LAST. MORNING TOP REPORTS OUT OF KSEA AND KBFI AROUND 2000 FEET. SATELLITE IMAGERY SHOWS THE CASCADE FOOTHILLS ARE CLEAR THIS MORNING. GRADIENTS ARE LIGHT OFFSHORE AND NOT EXPECTED TO CHANGE MUCH TODAY. ACARS SOUNDINGS SHOW A GOOD INVERSION OVER WESTERN WASHINGTON WITH THE TEMPERATURES AT 3000 FEET NEAR 50 DEGREES AND WINDS BELOW 850 MB LESS THAN 10 KNOTS. WITH THESE VARIABLES WILL UPDATE THE FORECAST FOR A SLOWER AND LESS EXTENSIVE BREAKOUT TODAY AND TONIGHT. NEXT SYSTEM STILL TIMED INTO THE AREA LATE TUESDAY NIGHT INTO WEDNESDAY BUT WITH THE CURRENT TRACK OF THE LOW AND THE FRONT BECOMING NEGATIVELY TILTED MIGHT HAVE TO SLOW DOWN THE TIMING OF THE SYSTEM IN THE AFTERNOON PACKAGE. UPPER LEVEL RIDGE OVER THE AREA TODAY SLIDING EAST LATER IN THE WEEK WITH MORE SYSTEMS REACHING WESTERN WASHINGTON IN THE SOUTHWESTERLY FLOW ALOFT. FOR NOW WILL JUST UPDATE THE FIRST COUPLE OF PERIODS IN THE ZONES THIS MORNING. FELTON

.LONG TERM...PREVIOUS DISCUSSION FOLLOWS. LOOK FOR AN UNSETTLED WEATHER PATTERN THIS WEAK AS THE MEAN UPPER RIDGE REMAINS OVER THE INTERMOUNTAIN W AND A MEAN TROF CONTINUES OFF THE W COAST. ENERGY ROTATING ACROSS THE AREA AT TIMES WILL KEEP THE WEATHER REGIME SOMEWHAT ACTIVE.

&&

.AVIATION...AIR MASS DOESN`T CHANGE MUCH OVER THE NEXT 24 HOURS...LOW LEVEL MOISTURE FOR FOG AND STRATUS...AND SOME MID AND HIGH CLOUDS. NOT MUCH MOISTURE FROM 2000 TO 12000 FEET HOWEVER. LIGHT GRADIENTS. MORE OF THE SAME A GOOD FCST.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...NONE.

$$

WEATHER.GOV/SEATTLE

HAVE DEBATED ISSUANCE OF YET ANOTHER ADVISORY FOR EARLY MORNING HOURS AS MODELS CONTINUE TO SHOW TREND FOR GRADIENT TIGHTENING OVERNIGHT AS HIGH PRESSURE BUILDS SOUTH INTO EASTERN WI. WINDS HAVE NOT DECOUPLED AS MUCH AS HOPED...HITTING THE MAGICAL 10 MPH RANGE IN PARTS OF CENTRAL WI. PROFILERS SHOWING INCREASING TREND IN LOW LEVEL WINDS PER MODEL FORECAST. SOME CONCERN ON EFFECTS OF DEVELOPING SURFACE INVERSION SEEN IN LATEST TAMDAR SOUNDINGS. TEMPERATURES ARE RUNNING SOME 5 DEGREES WARMER THAN PREVIOUS NIGHT...SO WILL STAY WITH LOW END ADVISORY. NO ADVISORY FOR EAST CENTRAL ATTM AS TEMPERATURES SLOWER TO FALL TONIGHT WITH LOWEST WIND CHILLS ONLY EXPECTED TO END UP AROUND -25

REMAINDER OF DISCUSSION FROM EARLIER SHIFT...

.SYNOPSIS...THE HIGH LATITUDE FLOW OVER NWRN NOAM AND THE NERN PAC WL BECOME INCREASINGLY BLOCKY AS LOW-LATITUDE PAC JET UNDERCUTS THE WRN NOAM/ERN PAC RIDGE AND WORKS EWD INTO THE WEST COAST. MEANWHILE... DOWNSTREAM TROF WL SHIFT E A BIT INTO THE NERN U.S. AND CANADIAN MARITIMES. THE RESULT WL BE A TREND TOWARD A MORE SPLIT-FLOW REGIME ACRS THE CONUS. THE MAIN DIFFERENCE BETWEEN THIS PATTERN AND THE TYPICAL SPLIT-FLOW PATTERN WL BE THE LINGERING WIDESPREAD ACRTIC AIR ACRS MUCH OF ERN NOAM.

ALTHOUGH THE ABV PATTERN CHGS WL EVENTUALLY LEAD TO MILDER WX ACRS THE AREA...THE EFFECT WON/T REALLY BE FELT UNTIL THE VERY END OF THE FCST PERIOD AND BEYOND. EXPECT THE MAIN SFC RIDGE AXIS TO REMAIN W OF THE AREA UNTIL TUE...SO WNWLY FLOW WL PROVIDE A CONTINUOUS FEED OF COLD AIR INTO THE RGN. EXPECT A COUPLE REINFORCING SHOTS OF COLD AIR...AND TEMPS REMAINING WELL BLO NORMAL.

THE FCST AREA WL REMAIN ENTRENCHED DEEPLY ENOUGH IN THE COLD AIR SO THAT PCPN CHCS WL BE LOW. FOR THE MOST PART...THE FLOW WL BE TOO WLY FOR SIG-LAKE EFFECT SNOW OFF LAKE SUPERIOR TO REACH THE FCST AREA. EVEN WHEN WINDS TURN MORE NLY WITH THE REINFORCING SHOTS OF COLD AIR...THE RAPIDLY INCRG ICE COVER ON WESTERN LAKE SUPERIOR WL GREATLY LIMIT THE POTENTIAL FOR LAKE-EFFECT SNOW. &&

.SHORT TERM...TONIGHT AND WEDNESDAY. FORECAST FOCUS ON WIND CHILLS LATE TONIGHT/EARLY WED MORNING.

GRADIENT EXPECTED TO TIGHTEN A BIT OVERNITE AS 925 MB WINDS INCREASE TO 25 KTS BY 06Z. HOWEVER WITH MOSTLY CLEAR SKIES ACROSS MUCH OF THE CWA THE WINDS SHOULD DECOUPLE AND KEEP SURFACE WINDS BELOW THE 10 MPH WIND CHILL ADVISORY THRESHOLD. DESPITE THE WINDS BELOW ADVISORY CRITERIA WIND CHILLS WILL STILL BE AROUND 30 BELOW ACROSS MUCH OF THE CWA LATE TONIGHT AND EARLY WEDNESDAY MORNING.

THE WINDS PICK UP WEDNESDAY MORNING WITH THE AREA BETWEEN LOW PRESSURE ACROSS SOUTHERN CANADA AND A RIDGE IN THE PLAINS. THE ATMOSPHERE SHOULD MIX ENOUGH TO PREVENT WIDESPREAD WIND CHILL ADVISORY CRITERIA DURING THE MORNING AS WINDS GO ABOVE 10 MPH. TEMPERATURES SHOULD WARM A FEW DEGREES MORE THAN TODAY WITH MIXING AND LESS CLOUDS.

GUIDANCE TEMPS CLOSE TONIGHT BUT SIDED WITH COOLER GFS FOR WED GIVEN THE BETTER PERFORMANCE TODAY.

.LONG TERM...WED NGT THROUGH TUE. MODELS STILL DIFFERED ON THE TIMING OF THE REINFORCING SHOTS OF COLD AIR. THE GFS SEEMED SOMEWHAT ERRATIC ON TIMING...AND LOOKED A BIT TOO STG ON SOME OF THE SHRTWVS ROTG SWD ACRS THE AREA. THE ECMWF SEEMED TO HAVE BETTER RUN-TO-RUN CONTINUITY...BUT NOT ENOUGH TO RAISE CONFIDENCE ENOUGH TO WORK MUCH DETAIL INTO THE FCST. SINCE THE COLD AIR WILL BE A LITTLE MORE SHALLOW THAN LAST WEEKEND... OVERNIGHT MINS WL PROBABLY DEPEND MORE ON WHETHER OR NOT THERE ARE CLOUDS AND DECOUPLING OF THE LOW-LEVEL WINDS. STAYED CLOSE TO PREV FCST AND BLO GUID ON TEMPS.

WENT WITH A DRY FCST. VISIBLE STLT IMAGES SHOWED SIG ICE ON WRN LAKE SUPERIOR. GIVEN THE CONTD COLD WX...THAT WL LIKELY EXPAND. EVEN A FAVORABLE 340 DEG TRAJECTORY MAY NOT GENERATE ENOUGH FETCH TO GET MUCH MORE THAN FLURRIES INTO VILAS COUNTY. BY NEXT TUE...THE MED RANGE MODELS INDICATED THE ERN TROF SHIFTING E AND ZONAL FLOW WORKING EWD ENOUGH TO RAISE THE POSSIBILITY OF GETTING SOME PCPN INTO THE FCST AREA. BUT THINK IT IS MORE LIKELY THAT THE SRN STREAM WL STILL BE S OF THE AREA...AND DEPARTING ARCTIC HIGH MAY LINGER LONGER IN THE CONFLUENT ZONE SETTING UP ACRS THE AREA. SEEMED LIKE THE BEST WAY TO GO WAS TO HAVE TUE DRY AND ALLOW LATER SHIFTS TO ADD PCPN IF LATER TRENDS WARRANT. &&

.AVIATION...VFR CIGS/VIS THRU WED. BKN SC CLDS FM 070-120 FT ACRS CNTRL/E-CNTRL WI BCMG FEW-SCT AROUND 00Z. &&

.GRB WATCHES/WARNINGS/ADVISORIES... NONE. &&

$$ WEATHER.GOV/GREENBAY

.SHORT TERM (TODAY AND TONIGHT)...

MAIN FORECAST CHALLENGE IN THE SHORT-TERM WILL BE TEMPERATURES TODAY AND TONIGHT.

SFC LOW AND ASSOCIATED WEAK CLIPPER THAT BROUGHT OUR NERN AREAS SOME SNOW LAST NIGHT HAS MOVED OFF TO THE SOUTHEAST AND EAST RESPECTIVELY. MVFR CIGS ASSOCIATED WITH THE LOW ARE QUICKLY DISSIPATING...SO WILL CLEAR OUT SKIES SOONER THAN WHAT MODELS INDICATED.

SNOW COVER FROM YESTERDAY`S SYSTEM RANGES FROM A DUSTING ROUGHLY FROM SALEM INDIANA TO LANCASTER KENTUCKY...TO 4 TO 5 INCHES ACROSS THE FAR NRN BLUEGRASS...NAMELY IN BOURBON...NICHOLAS AND HARRISON COUNTIES. THIS WILL MAKE IT DIFFICULT FOR TEMPS TO RISE TODAY...ESPECIALLY WHERE THE SNOW DEPTHS ARE HIGHEST. THINK THAT MOS GUIDANCE MAY BE MISSING THESE DETAILS...SO WILL LOWER TEMPS ACROSS OUR NERN CWA FOR TODAY. THINK THAT THE HIGHS WILL BE MET EARLY THIS MORNING FOR LOCATIONS NE OF A LINE FROM SCOTTSBURG INDIANA TO LEXINGTON. MET GUIDANCE IS CLOSER TO BEING RIGHT I FEEL...BUT WILL STILL UNDERCUT A FEW DEGREES. WILL LIKELY HAVE A STEADY TEMP WORDING IN THE ZONES. SKIES SHOULD ONLY BE PARTLY CLOUDY FOR THE MOST PART...AS SFC HIGH PRESSURE NOSES IN FROM THE WEST. WINDS WILL BE LIGHT (5-10MPH) FROM THE NORTHWEST FOR MUCH OF THE DAY.

FOR TONIGHT...ANOTHER FAST-MOVING SPEED MAX WILL MOVE ACROSS OUR CWA. HOWEVER...SREF HAS NOTHING IN THE WAY OF QPF OVER US...DESPITE GFS SHOWING SLT CHC POPS IN THE MOS OUTPUT. WILL CONTINUE DRY FORECAST...THOUGH A FEW FLURRIES COULD CERTAINLY OCCUR. MAY INSERT THIS INTO THE NWRN CWA AFTER 00Z. THE SPEED MAX WILL AT LEAST INCREASE MID AND UPPER LEVEL CLOUD COVER TOWARD SUNSET...BUT THIS PROBABLY WILL NOT BE ENOUGH TO PREVENT TEMPS FROM PLUMMETING UNDER THE WEAK SFC HIGH. WILL AGAIN UNDERCUT GUIDANCE TONIGHT...AS CALMING WINDS AND CONTINUED SNOW COVER WILL ALLOW TEMPS ACROSS THE NRN BLUEGRASS TO DROP BELOW 10 DEGREES FOR OVERNIGHT LOWS.

AL

.LONG TERM (THURSDAY THROUGH TUESDAY)...

FAIRLY UNEVENTFUL FORECAST. EARLY IN THE PERIOD A DRY NORTHWEST FLOW WILL PREVAIL. WEAK DISTURBANCES WILL ROTATE SOUTH OUT OF EASTERN CANADA BUT PRECIPITATION WILL REMAIN WELL NORTHEAST OF THE LOWER OHIO VALLEY. WITH THIS NORTHWEST FLOW TEMPERATURES WILL REMAIN COLD AVERAGING SOME 10 TO 15 DEGREES BELOW NORMAL.

THE UPPER LEVEL FLOW WILL BEGIN TO FLATTEN OUT SATURDAY AS THE WEST COAST RIDGE BREAKS DOWN. THIS WILL CREATE A SPLIT FLOW ACROSS THE REGION. A COUPLE OF RIPPLES IN THE SOUTHERN FLOW WILL BE CAPABLE OF PRODUCING SOME PRECIPITATION ACROSS THE FORECAST AREA. THE 00Z GFS SHOWS SOME MOISTURE OVERSPREADING THE REGION SUNDAY BUT THE GFS ENSEMBLE MEMBER AVERAGES KEEP THE MOISTURE SOUTH OF KENTUCKY SO WE WILL HOLD ONTO A DRY FORECAST. A BETTER CHANCE FOR PRECIPITATION WILL OCCUR MONDAY NIGHT AND TUESDAY AND WILL HOLD ONTO LOW POPS FOR THAT TIME FRAME. --JA

.AVIATION (06Z TAFS)...

CURRENTLY...SFC LOW OVER SERN KY...WHERE 3.5-6KFT CIGS WERE MOVING QUICKLY TO THE EAST. 00Z NAM12 LOW-LEVEL MOISTURE FIELDS VERIFY CURRENT CLOUDS WELL...SO WILL FOLLOW FOR CLOUD TRENDS. A BREAK IN THE CLOUDS CAN BE SEEN ACROSS WRN KY ATTM...HOWEVER LOW MVFR CIGS UPSTREAM ACROSS IL/IN MAY FILTER INTO CLEAR AREAS. NAM MOVES THESE CLOUDS SE OF THE SDF TAF SITE BY ROUGHLY 18Z...AND DISSIPATES THE CLOUDS BY 00Z ACROSS THE LEX AND BWG TAF SITES. HOWEVER MOS GUIDANCE IS MORE OPTIMISTIC...AND WITH SFC HIGH PRESSURE NOSING IN FROM THE NW TODAY...WILL TREND TOWARD THE MOS GUIDANCE INSTEAD. STRONG UPPER JET WILL FORCE CIRRUS SHIELD INTO CENTRAL KY THIS MORNING AND AFTERNOON...SO WILL TREND FROM IFR/MVFR TO VFR CIRRUS BY LATE MORNING AT SDF...AND ROUGHLY NOON/1PM EST AT LEX AND BWG. A FEW FLURRIES MAY BE POSSIBLE EARLY THIS MORNING IN THE LOW STRATO-CU...BUT SHOULD POSE NO AVIATION PROBLEMS AND WOULD LIKELY ONLY BE AT THE LEX TAF SITE.

AS FAR AS WINDS ARE CONCERNED...THEY ARE GUSTY AND SWRLY ACROSS SRN KY CAUSED BY A 50-70KT WLY LLJ...AND WINDS ARE LIGHT AND N/NWRLY ACROSS SRN IN AND N-CNTRL KY...BEHIND THE SFC LOW. ANY GUSTY WINDS WILL DISSIPATE OVER THE NEXT FEW HOURS...WITH NWRLY 6-9 KTS RULING. WILL HOLD ONTO WIND SHEAR AT BWG FOR THE NEXT FEW HOURS BASED OFF OF OHX ACARS SOUNDING.

AL

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

.AVIATION (06Z TAFS)...

CURRENTLY...SFC LOW OVER SERN KY...WHERE 3.5-6KFT CIGS WERE MOVING QUICKLY TO THE EAST. 00Z NAM12 LOW-LEVEL MOISTURE FIELDS VERIFY CURRENT CLOUDS WELL...SO WILL FOLLOW FOR CLOUD TRENDS. A BREAK IN THE CLOUDS CAN BE SEEN ACROSS WRN KY ATTM...HOWEVER LOW MVFR CIGS UPSTREAM ACROSS IL/IN MAY FILTER INTO CLEAR AREAS. NAM MOVES THESE CLOUDS SE OF THE SDF TAF SITE BY ROUGHLY 18Z...AND DISSIPATES THE CLOUDS BY 00Z ACROSS THE LEX AND BWG TAF SITES. HOWEVER MOS GUIDANCE IS MORE OPTIMISTIC...AND WITH SFC HIGH PRESSURE NOSING IN FROM THE NW TODAY...WILL TREND TOWARD THE MOS GUIDANCE INSTEAD. STRONG UPPER JET WILL FORCE CIRRUS SHIELD INTO CENTRAL KY THIS MORNING AND AFTERNOON...SO WILL TREND FROM IFR/MVFR TO VFR CIRRUS BY LATE MORNING AT SDF...AND ROUGHLY NOON/1PM EST AT LEX AND BWG. A FEW FLURRIES MAY BE POSSIBLE EARLY THIS MORNING IN THE LOW STRATO-CU...BUT SHOULD POSE NO AVIATION PROBLEMS AND WOULD LIKELY ONLY BE AT THE LEX TAF SITE.

AS FAR AS WINDS ARE CONCERNED...THEY ARE GUSTY AND SWRLY ACROSS SRN KY CAUSED BY A 50-70KT WRLY LLJ...AND WINDS ARE LIGHT AND N/NWRLY ACROSS SRN IN AND N-CNTRL KY...BEHIND THE SFC LOW. ANY GUSTY WINDS WILL DISSIPATE OVER THE NEXT FEW HOURS...WITH NWRLY 6-9 KTS RULING. WILL HOLD ONTO WIND SHEAR AT BWG FOR THE NEXT FEW HOURS BASED OFF OF OHX ACARS SOUNDING.

AL

&&

.PREV DISCUSSION...

MESO UPDATE/840 PM EST... WE WILL BE DROPPING ALL HEADLINES WITH THIS UPDATE. BULK OF SIGNIFICANT PRECIP WILL EXIT THE LMK CWA BY 2Z/9PM EST WITH ONLY POCKETS OF LIGHT PRECIP EXPECTED OVER OUR ERN ZONES THROUGH MIDNIGHT. A STATEMENT CONTAINING STORM TOTAL SNOW/ICE AMOUNTS WILL BE ISSUED THIS EVENING...UNDER THE PNSLMK IDENTIFIER...AND ALSO POSTED TO OUR TOP-NEWS SECTION AT WEATHER.GOV/LOUISVILLE. WITH HEADLINES BEING DROPPED...WE WILL ISSUE AN SPS FOR MUCH OF THE NORTHERN 1/2 OF THE CWA HIGHLIGHTING SLICK SPOTS OVERNIGHT INTO THE EARLY MORNING DRIVE TIME. WILL ALSO MENTION WIND CHILLS NEARING ZERO BY DAYBREAK.

IMPRESSIVE TEMPERATURE CONTRAST ATTM OVER THE CWA...WITH NEAR 50F OVER FAR SRN KY...TO THE LOWER 20S IN THE NRN BLUEGRASS. FOR THE REMAINDER OF THE NIGHT...AS SFC LOW TRACKS EAST THROUGH THE CWA...WINDS WILL SWITCH TO A NORTHERLY DIRECTION WITH AN AREA OF LOW CLOUDS MOVING BACK INTO THE REGION. BANDS OF -SN CURRENTLY OVER CNTRL/NRN IN FCST BASED ON RADAR TRAJECTORIES TO REMAIN WELL N OF THE LMK CWA...THOUGH IF CIGS BECOME LOW ENOUGH WE COULD SEE SOME SPOTTY -FZDZ OR FLURRIES LATE TONIGHT.

REGARDING THE EARLIER WARM SURGE ALOFT...NOTICED AN INTERESTING OBSERVATION: PILOT REPORT NEAR HOP AT 21Z CHECKED IN WITH A SSW WIND OF 57KTS AT 4000FT AGL. IMPRESSIVE LLJ!

UPDATED PRODUCTS SHOULD BE OUT BY 930 PM EST.

CS/MBS

SHORT TERM (TONIGHT AND WEDNESDAY)...

COMPLICATED FORECAST IN THE NEAR TERM AS TO DETERMINE WHERE SNOW ACCUMULATION GRADIENT WILL FALL. LOOKING OVER THE PAST FEW MODEL RUNS...IT APPEARS THAT THE NAM-WRF SOLUTION HAS BEEN A BIT MORE CORRECT WITH THE OVERALL PLACEMENT WITH THE HEAVIEST SNOW BAND. THE GFS IS PARTIALLY CORRECT TOO...BUT HAS BEEN OVERDOING SOME OF THE PRECIPITATION AMOUNTS IN ITS SOLUTIONS. THE 12Z STILL HAVE SOME DISAGREEMENT WITH THE PLACEMENT OF THE HEAVIEST SNOW BAND. WITH THE WRF SOLUTION BEING JUST NORTH OF THE FA...WHILE THE GFS IS A BIT MORE SOUTH. SFC LOW OVER CENTRAL MISSOURI IS FCST TO DROP INTO WESTERN KY THIS EVENING AND THEN HEAD EAST. THE GFS SHOWS AN ENHANCEMENT OF QPF OVER THE NE PORTION OF THE FA THIS EVENING AND OVER IN EASTERN KY OVERNIGHT AS UPSLOPE FORCING HELPS MAINTAIN SNOW AND SNOW SHOWERS. HAVE CHOSEN TO GO WITH A NAM-WRF COMPROMISE WHICH WILL RESULT IN CHANGES TO THE ONGOING FCST.

FIRST...THE HEAVY SNOW WARNING STILL LOOKS GOOD FOR OUR NORTHEASTERN COUNTIES. A TOTAL OF THREE TO SIX INCHES STILL WILL BE POSSIBLE IN THIS AREA. HOWEVER THE BEST CHANCES OF SEEING THOSE HIGHER ACCUMULATIONS WILL BE ACROSS NORTH OF A FRANKFORT TO PARIS LINE. ITS A REAL TOUGH CALL IN THE LEXINGTON METRO AREA AS THE NORTHERN PORTION OF THE COUNTY HAS RECEIVED A DECENT AMOUNT OF SNOW...WHILE THE SOUTHERN PART OF THE COUNTY HAS NOT. THIS IS ALSO THE CASE IN LOUISVILLE WHERE WE HAVE DUSTING HERE...BUT JUST OUTSIDE THE COUNTY WE HAVE 1/2 TO 1 INCH REPORTS ACROSS OLDHAM COUNTY.

A SHARP GRADIENT OF SNOW ACCUMULATION IS LIKELY AND PORTIONS OF THE COUNTIES IN THE WARNING AREA MAY HIT THE CRITERIA...WHILE OTHER PORTIONS DO NOT. FURTHER SOUTH AND WEST...WE PLAN ON TRIMMING BACK THE SNOW ADVISORY. PLAN ON RUNNING THIS FROM WASHINGTON COUNTY INDIANA THROUGH LOUISVILLE METRO AND DOWN TO GARRARD COUNTY. IN THIS AREA...A GENERAL 1 TO 3 INCHES OF ACCUMULATION WILL BE POSSIBLE. UPSTREAM RADAR SHOWS ANOTHER BATCH OF SNOW SHOWERS COMING INTO OUR NORTHWEST PORTIONS WHICH WILL HIT THIS ADVISORY AREA LATER THIS EVENING. ACROSS THE SOUTHWEST...MAINLY DRY CONDITIONS ARE EXPECTED TONIGHT. IN THE FAR SOUTHEAST...SOME PRECIPITATION MAY LINGER DOWN CLOSE THE SOMERSET AREA WHERE P-TYPE WILL BE A MIX OF RAIN/FZRA/PL/SNOW. AM NOT CONFIDENT ON AMOUNTS OR COVERAGE...BUT WILL KEEP A CHC IN. ACCUMULATIONS IN THIS AREA WOULD BE LITTLE OR NONE.

SNOW WILL EXIT THE REGION LATER TONIGHT FROM NORTHWEST TO SOUTHEAST...SO WILL LEAVE CURRENT ADVISORY/WARNING ENDING TIMES AS IS AND LET FUTURE SHIFTS TRIM BACK AS NECESSARY. TEMPERATURES IN THE SNOW COVERED AREAS WILL DROP OFF INTO THE TEENS LATER TONIGHT WITH LOWER TO MID 20S DOWN ACROSS THE SOUTH. MOSTLY CLOUDY SKIES WILL START OFF THE DAY ON WEDNESDAY WITH SOME CLEARING NOTED IN THE AFTERNOON. NORTH WINDS WILL KEEP TEMPERATURES BELOW NORMAL ONCE AGAIN...ESPECIALLY IN AREAS THAT HAVE SNOW PACK. IN GENERAL HAVE GONE CLOSER TO 2M RAW MODEL OUTPUT FOR THIS FORECAST PERIOD.

THANKS TO JKL/IND/PAH AND LEX MEDIA FOR COORDINATION THIS AFTERNOON.

-MJ

LONG TERM (WEDNESDAY NIGHT THROUGH TUESDAY)...

THE VERY COLD ARCTIC AIR MASS HAS SHIFTED OFF TO THE NORTHEAST...BUT SYSTEMS ROTATING SOUTHEAST ACROSS THE NORTH CENTRAL U.S. AROUND THE COLD VORTEX OVER EAST CENTRAL CANADA WILL KEEP SOME COLD ARCTIC AIR FLOWING ACROSS THE REGION DURING THE NEXT FEW DAYS...BUT THIS AIR IS RELATIVELY DRY SO NO REALLY GOOD PRECIPITATION CHANCES FOR THE NEXT FEW DAYS. MAX AND MIN TEMPS SHOULD AVERAGE SOME 10 TO 15 DEG BELOW THE SEASONAL NORMALS FOR THIS TIME OF YEAR.

BY THE WEEKEND AND INTO THE NEXT WORKWEEK A SERIES OF PACIFIC TROUGHS OFF THE WEST COAST OF THE U.S. WILL EVENTUALLY ESTABLISH MORE OF A SPLIT FLOW PATTERN. THIS NEW SOUTHERN STREAM WILL LIKELY SET UP EAST TO WEST ACROSS THE SOUTH CENTRAL U.S. GIVEN THAT THE THE COLD AIR WILL STILL BE IN PLACE ACROSS THE REGION DUE TO THE NORTHERN STREAM...THIS SCENARIO COULD EVENTUALLY EVOLVE INTO ONE OR MORE RAIN/SNOW PRODUCING STORM SYSTEMS LATE IN THE PERIOD AND BEYOND.

ONE SUCH STORM SYSTEM IS FORECAST BY THE GFS AND THE LATEST HPC EXTENDED GUIDANCE PICKS UP ON THIS TOO. THIS LOOKS OK TO US TOO. WE WILL INTRODUCE A CHANCE OF LIGHT SNOW ON MONDAY NIGHT AND A CHANCE FOR A RAIN OR SNOW MIX ON TUESDAY. --21

&&

.LMK WATCHES/WARNINGS/ADVISORIES... KY...NONE. IN...NONE. &&

$$

.SYNOPSIS... A DEVELOPING TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC WILL BRING A COOLING TREND AND INCREASING CLOUDS THROUGH FRIDAY. THIS TROUGH OF LOW PRESSURE MAY MOVE INLAND ACROSS CALIFORNIA DURING THE WEEKEND THROUGH EARLY NEXT WEEK BRINGING A CHANCE OF PRECIPITATION TO SOUTHWEST CALIFORNIA.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

.SHORT TERM (TODAY THROUGH FRIDAY)... DENSE FOG ADVISORY EXTENDED FOR COASTAL AREAS UNTIL 8 AM AND EXPANDED INTO THE SAN DIEGO COUNTY VALLEYS. ACARS SOUNDINGS SHOW A SHALLOW MARINE INVERSION WITH THE BASE BELOW 1000 FEET. SURFACE REPORTS SHOW AREAS OF DENSE FOG PERSISTING ALONG THE COAST EXTENDING INLAND TO THE LOWER COASTAL VALLEYS. SOME DEEPENING OF THE MARINE LAYER IS EXPECTED WITH THE APPROACHING TROUGH OVER THE EASTERN PACIFIC THOUGH THIS HAS BEEN SLOW TO OCCUR. SOME DEEPENING IS SUGGEST BY SURFACE OBSERVATIONS IN SAN DIEGO COUNTY THE PAST TWO HOURS WITH SOME SLOW IMPROVEMENT IN THE VISIBILITY AT LINDBERGH FIELD WITH DENSE FOG SPREADING INLAND TO MIRAMAR AND MONTGOMERY. WHILE SOME SLOW DEEPENING MAY OCCUR THROUGH SUNRISE...THIS MAY NOT BE SUFFICIENT OR FAST ENOUGH TO RESULT IN WIDESPREAD IMPROVEMENT IN VISIBILITIES IN THE COASTAL ZONES UNTIL SOME TIME AFTER 6 AM.

OTHERWISE...THE DEVELOPING TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC WILL CONTINUE THE COOLING TREND THROUGH FRIDAY WITH VARIABLE HIGH CLOUDS AND SOME OVERNIGHT MARINE LAYER CLOUDINESS. PRECIPITATION THROUGH FRIDAY WILL MOSTLY BE DIRECTED INTO NORTHERN AND CENTRAL CALIFORNIA...THOUGH THERE`S A SMALL CHANCE THAT LIGHT PRECIPITATION COULD EXTEND INTO PORTIONS OF SOUTHERN CALIFORNIA AT TIMES...MAINLY THURSDAY AND FRIDAY.

&&

.LONG TERM (SATURDAY THROUGH TUESDAY)... THE TROUGH OF LOW PRESSURE OVER THE EASTERN PACIFIC WILL GRADUALLY PROGRESS INLAND ACROSS CALIFORNIA DURING THE WEEKEND THROUGH EARLY NEXT WEEK WITH MODELS STILL LACKING CONSISTENCY WITH SHORTWAVE DETAILS. THE OVERALL PATTERN IS ONE THAT SHOULD FAVOR INCREASING CHANCES FOR PRECIPITATION FOR SOUTHWEST CALIFORNIA WITH SOME POTENTIAL FOR SIGNIFICANT PRECIPITATION. GREATEST AGREEMENT...SUCH AS IT IS...IS SATURDAY/SUNDAY...WITH LESS AGREEMENT FOR TRAILING SHORTWAVES MONDAY/TUESDAY.

&&

.AVIATION... A WEAK EDDY HAS ALLOWED A SHALLOW 500 FT DEEP MARINE LAYER TO SPREAD INLAND ACROSS MOST OF THE COASTAL PLAINS...RESULTING IN AREAS OF DENSE FOG AND VERY LOW CEILINGS...WITH VISIBILITY BELOW 1/4 MILE AT MANY COASTAL LOCATIONS. NOT MUCH DEEPENING WILL OCCUR...SO EXPECT THE FOG TO AFFECT THE COASTAL AIRPORTS THROUGH 16Z. AN APPROACHING TROUGH SHOULD DEEPEN THE MARINE LAYER THIS AFTERNOON. DEEPER MORE EXTENSIVE MARINE LAYER EXPECTED EARLY EVENING LASTING WELL INTO THURSDAY MORNING. WINDS AT 10K FT MOSTLY SW 15 TO 20 KT TODAY. OTHERWISE GOOD VIS WITH 25K FT HIGH CIRRUS CLOUDS CONTINUING.

&&

.SGX WATCHES/WARNINGS/ADVISORIES... CA...DENSE FOG ADVISORY UNTIL 8 AM PST THIS MORNING FOR ORANGE COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS-SAN DIEGO COUNTY VALLEYS.

PZ...NONE.

&&

$$

PUBLIC...MARTIN AVIATION/MARINE...MACKECHNIE

NWS ON THE WEB AT WEATHER.GOV/SANDIEGO

.AVIATION... LIGHT LAKE EFFECT SNOW SHOWERS AREA EXPECTED TO PERSIST THROUGH THE TAF PERIOD. HOWEVER...CIGS/VSBYS ARE EXPECTED TO REMAIN MAINLY VFR. UPSTREAM ACARS SOUNDINGS SHOW VERY LOW INVERSION HEIGHTS WITH A RELATIVELY DRY LAYER BELOW THE INVERSION. FLOW FROM THE WNW TO THE NW WILL HELP KEEP THE SW EDGE OF THE LAKE EFFECT BANDS CLOSE TO SBN AND FWA.

&&

.SHORT TERM... TODAY AND TONIGHT...ARCTIC AIR WILL CONTINUE TO SPREAD ACROSS LAKE MICHIGAN TODAY AND TONIGHT...AND CONTINUE TO PRODUCE SOME LAKE EFFECT SNOW SHOWERS. ALTHOUGH DELTA T VALUES CLOSE TO 20...SEVERAL OTHER FACTORS ARE NOT THAT FAVORABLE FOR HEAVY LAKE EFFECT SNOW SHOWERS. THESE INCLUDE LOW TO MID LEVEL SUBSIDENCE...RELATIVE LOW INVERSION HEIGHTS...LIMITED TRAJECTORIES OVER LAKE MICHIGAN AND A DRY AIRMASS UPSTREAM. HIGH WATER TO SNOW RATIOS SHOULD PROVIDE SNOW ACCUMULATION UP TO AN INCH WITH ONLY UP TO 3 HUNDREDTHS OF WATER EQUIVALENT. FOR TONIGHT...LOWERED TEMPERATURES SEVERAL DEGREES OVER AREAS AWAY FROM LAKE MICHIGAN. ADDITIONAL SNOW ACCUMULATION OF 2 TO 5 INCHES YESTERDAY WITH SOME CLEARING SKIES TONIGHT SHOULD ALLOW TEMPERATURES DROP CLOSE TO ZERO OVER MUCH OF THE AREA. UPSTREAM TEMPERATURES OVERNIGHT WERE ALREADY BELOW -10F IN SOME LOCATIONS OF NORTHERN IL. EXPECT UP TO ANOTHER INCH OF SNOW TONIGHT IN BERRIEN AND CASS COUNTIES OF FAR SW LOWER MICHIGAN AS LAKE EFFECT SNOW PERSISTS.

&&

.LONG TERM...

FEW CHANGES TO LONG TERM GRIDS THIS MORNING. CURRENT FORECAST GENERALLY ON TRACK THOUGH MODEL DIFFERENCES AND INCONSISTENCIES RAISE SOME DOUBT DURING A FEW PERIODS. GIVEN THIS UNCERTAINTY FELT IT PRUDENT TO ALLOW GRIDS TO RIDE FOR ANOTHER RUN OR TWO.

STILL EXPECT A GRADUAL DEAMPLIFICATION TO THE OVERALL LONG WAVE PATTERN THROUGH THE PERIOD. HOWEVER...TEMPERATURE MODERATION WILL BE SLOW WITH GENERALLY BELOW NORMAL READINGS STILL EXPECTED RIGHT THROUGH THIS LONG TERM PERIOD. OF SOME CONCERN IS YET ANOTHER SHORT WAVE DIVING SOUTH OUT OF THE NORTH POLE REGION WITH CROSS POLAR FLOW LATE THIS WEEK. AS THE LONG WAVE PATTERN DEAMPLIFIES...BULK OF COLD AIR WITH THIS WAVE GETS SHUNTED EAST THROUGH ONTARIO AND REMAINS WELL NORTH OF OUR AREA. CERTAINLY SOMETHING TO MONITOR AS THIS WAVE CURRENTLY OUTSIDE OF GOOD UPPER AIR NETWORK AND THINGS COULD CERTAINLY CHANGE GIVEN OUR RECENT PATTERN.

OTHERWISE...GENERALLY LIGHT LAKE EFFECT EXPECTED TO CONTINUE NEAR LAKE MICHIGAN WITH DELTA T VALUES IN THE TEENS AND FLOW OFF THE LAKE. A WAVE THURSDAY NIGHT AND FRIDAY WILL HELP TURN WINDS MORE NORTHERLY WITH ANOTHER POSSIBLE MESO LOW TO FORM ON EASTERN SIDE OF LAKE MICHIGAN. NAM 925MB PLUME ANALYSIS STILL INDICATES POSSIBLE SHORE PARALLEL SINGLE BAND DEVELOPING. HOWEVER...WINDS QUICKLY BACK DURING THE DAY FRIDAY AND THIS BAND WOULD THEN MOVE EAST AND DISSIPATE. HOWEVER...AS WE SAW LAST WEEK...IF IT INDEED FORMS IN ASSOCIATION WITH A MESO LOW AND VORTICITY CENTER...CERTAINLY COULD SEE INTENSE SNOW BANDS FOR A BRIEF PERIOD. LAST NIGHT GRIDS HAD THIS ACCOUNTED FOR BUT WERE REMOVED ON PREVIOUS SHIFT. HAVE ADDED CHANCE POPS BACK IN FOR LAPORTE...STARKE AND NORTHERN PULASKI COUNTY. THIS MAY BE A BIT FAR SOUTH BUT WOULD NOT BE SURPRISED TO SEE SNOW SHOWERS THIS FAR SOUTH GIVEN THE LONG FETCH THAT WOULD BE IN PLACE. WILL CONTINUE TO MONITOR MODEL TRENDS WITH THIS FEATURE OVER THE NEXT FEW DAYS.

NO OTHER CHANGES TO LATER PERIODS WITH THIS PACKAGE. MAY NEED TO EVENTUALLY ADD SNOW CHANCES FOR EARLY NEXT WEEK AS LOW DEVELOPS IN THE SOUTHERN PLAINS AND MOVES INTO GULF COAST REGION. MODELS CURRENTLY JUST BRUSHING OUR SOUTHERN COUNTIES BUT WE REMEMBER THE EARLY WINTER PATTERN WHEN THE SOUTHERN STREAM LOWS LIFTED OUT WELL NORTH OF MEDIUM RANGE PROJECTIONS. STILL PLENTY OF TIME TO MONITOR AND ADD POPS BUT THIS SYSTEM HAS THE POTENTIAL FOR QUITE A BIT OF QPF AND HEAVY SNOW IN THE COLD SECTOR...WHEREVER THAT SETS UP. $$

.IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST THURSDAY FOR LMZ043-046.

&&

$$

AVIATION/SHORT TERM...SKIPPER LONG TERM...LASHLY