FXUS61 KILN 080251
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
951 PM EST MON DEC 7 2009

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY TONIGHT...THEN
QUICKLY SLIDE EAST OF THE REGION BY TUESDAY MORNING. A STRONG LOW
PRESSURE SYSTEM WILL MOVE INTO THE SOUTHERN PLAINS AND OZARKS
TUESDAY EVENING...AND DEEPEN AS IT TRACKS INTO THE GREAT LAKES ON
WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
SFC HIGH PRESSURE TO SLIDE EAST ACROSS THE REGION TONIGHT. LATEST
SATL IMAGERY SHOWS A GOOD DEAL OF LOW CLDS OVER THE REGION WITH AN 
AREA OF BREAKS DEVELOPING ACROSS NW OHIO. THE LOW CLDS HAVE BEEN SLOW
TO THIN OUT AND MSTR AT H5 AND ABOVE IS ALREADY OVERSPREADING THE
LOW CLDS. THEREFORE...HAVE INCREASED CLOUD COVER AND NUDGED UP 
OVERNIGHT LOWS SLIGHTLY. 

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
STRONG WINTER STORM TO TRACK ACROSS THE MIDWEST TUESDAY AND
WEDNESDAY AND IS THE FOCUS THIS FORECAST PACKAGE. MODELS REMAIN IN
REMARKABLY GOOD AGREEMENT ON SFC LOW TRACK...TAKING IT FROM
CENTRAL MISSOURI TUESDAY EVENING INTO THE CENTRAL GREAT LAKES ON
WEDNESDAY. THIS KEEPS THE CWA IN THE WARM SECTOR AS THE SFC
LOW TRACKS NORTHWEST OF THE REGION. 

DEEP LOW LEVEL ISENTROPIC LIFT WILL QUICKLY OVERSPREAD THE AREA
FROM THE SOUTH TUESDAY MORNING. WHILE LOW LEVELS WILL INITIALLY BE
DRY...ISENTROPIC LIFT LOOKS STRONG AND DEEP ENOUGH THAT PRECIP
COULD BEGIN REACHING THE GROUND FASTER THAN THE MODELS ARE
INDICATING. THIS MAY BECOME PROBLEMATIC SINCE LOW LEVEL WETBULB
VALUES WILL STAY NEAR OR BELOW FREEZING ACROSS MUCH OF THE CWA
THROUGH THE MORNING AND EARLY AFTERNOON. THUS...ANY PRECIP
FALLING INTO THE DRY LOW LEVEL AIRMASS WILL LIKELY COOL THE
BOUNDARY LAYER ENOUGH FOR PRECIP TO INITIALLY TAKE THE FORM OF
SLEET OR SNOW. THIS PRECIP SHOULD BE LIGHT ENOUGH SO THAT LITTLE
IF ANY SLEET OR SNOW ACCUMULATION SHOULD OCCUR...BUT WILL NEED TO
MONITOR IN CASE PRECIP BECOMES HEAVIER. AT THIS TIME...THERMAL
PROFILES SUPPORT MORE SLEET AND SNOW THAN FREEZING RAIN...SO DID
NOT MENTION ICING IN THE FORECAST ALTHOUGH IT CERTAINLY CANNOT BE
RULED OUT.

LOW LEVEL WARM FRONT WILL MOVE NORTH OF THE OHIO RIVER BY LATE
TUESDAY AFTERNOON. THIS WILL ALLOW PRECIP TO BECOME ALL RAIN
ACROSS AREAS SOUTH OF I-70 BY TUES AFTERNOON. DEEP LIFT ALONG THE
FRONT WILL CAUSE WIDESPREAD PRECIP TO OVERSPREAD THE ENTIRE AREA
FROM THE SOUTH TUESDAY AFTERNOON THROUGH TUESDAY EVENING...AS THE
FRONT LIFTS NORTH OF THE CWA BY LATE TUESDAY EVENING. STEADY WARM
AIR ADVECTION WILL CHANGE ALL PRECIP TO RAIN BY EARLY TUESDAY
EVENING ACROSS THE ENTIRE REGION. HEAVIER PRECIP RATES MAY REACH
THE NORTHERN CWA BEFORE PRECIP CHANGES TOTALLY OVER TO RAIN
THERE...AND THIS AREA WILL NEED TO BE WATCHED FOR ANY ACCUMULATING
SNOW OR SLEET EARLY TUESDAY EVENING. FOR NOW...EXPECT PRECIP TO
BECOME ALL RAIN QUICK ENOUGH TO PREVENT MUCH ACCUMULATION.

DEEP FRONTAL CONVERGENCE AND ISENTROPIC LIFT OVERSPREADS THE AREA
THROUGH EARLY WEDNESDAY WITH WIDESPREAD RAIN ACROSS THE ENTIRE CWA
OVERNIGHT. PRECIP RATES WILL BE ENHANCED FROM DEEP CONVERGENCE AND
WEAK CONVECTIVE INSTABILITY...WHICH MAY GIVE UP TO AN INCH OF
RAINFALL...ESPECIALLY ACROSS THE SOUTHEAST CWA. EXPECT PRECIP TO
QUICKLY DECREASE IN COVERAGE FROM SOUTHWEST TO NORTHEAST BETWEEN
09Z AND 13Z WEDS AS COLD FRONT SWINGS THROUGH AND STRONG CAA GETS
UNDERWAY. THIS WILL BRING A CHANGEOVER FROM RAIN TO SNOW FROM WEST
TO EAST THROUGH THE DAY WEDNESDAY. HOWEVER...BULK OF THE LIFT WILL
BE WELL NORTHEAST OF THE CWA BY THIS TIME...AND PRIMARY FORCING
WILL BE OCCASIONAL MIDLEVEL PVA IN THE VICINITY OF THE UPPER
TROUGH...WHICH WILL PROVIDE JUST ENOUGH FORCING FOR SCATTERED RAIN
OR SNOW SHOWERS WILL LITTLE IF ANY SNOW ACCUMULATION.

MAIN STORY ON WEDNESDAY IS THE STRONG WIND FIELD WHICH WILL MOVE
IN BEHIND THE ANOMALOUSLY DEEP SURFACE CYCLONE. STRENGTH OF SFC
LOW WILL BE AS MUCH AS 3.5 STANDARD DEVIATIONS BELOW
CLIMATOLOGICAL MEANS FOR DECEMBER...WHICH WILL TRANSLATE INTO A
VERY TIGHT PRESSURE GRADIENT ACROSS PARTS OF THE MIDWEST WITH
WINDS STRONGER THAN THIS AREA HAS SEEN IN MANY MONTHS. 850 HPA
WINDS ANYWHERE BETWEEN 50 AND 65 KT COMBINED WITH STRONG LOW LEVEL
COLD AIR ADVECTION AND GOOD MOMENTUM TRANSFER WILL BRING SURFACE WIND
GUSTS BETWEEN 40 AND 50 KT WEDNESDAY AFTERNOON. CRITERIA FOR A
HIGH WIND WARNING IS 50-KT GUSTS WHICH MAY OR MAY NOT BE MET ON
WEDNESDAY. HOWEVER...EVEN IF GUSTS ONLY REACH 45-49 KT
RANGE...WINDS WILL BE PROLONGED ENOUGH THAT THE POTENTIAL STILL
EXISTS FOR WIDESPREAD IMPACTS FROM THIS WIND EVENT INCLUDING
DOWNED LIMBS AND POWER OUTAGES. THEREFORE A HIGH WIND WATCH HAS
BEEN ISSUED FOR THE ENTIRE CWA FROM 12Z WEDS TO 06Z THURS. LATER
SHIFTS CAN MONITOR MODEL TRENDS TO SEE IF MAGNITUDE OF WIND GUSTS
WILL WARRANT A WIND ADVISORY OR AN UPGRADE TO A HIGH WIND WARNING.
WINDS WILL SUBSIDE ON WEDS NIGHT AS LOW TRACKS INTO SOUTHEAST
CANADA...AND ANY LINGERING SNOW SHOWERS OR FLURRIES WILL TAPER OFF
AFTER MIDNIGHT.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
SURFACE HIGH PRESSURE WILL BEGIN TO BUILD IN FROM THE SOUTHWEST
THURSDAY. THE PRESSURE GRADIENT IS STILL FAIRLY TIGHT THROUGH THE
DAY ON THURSDAY THOUGH AND WITH CONTINUING CAA...BRISK WINDS CAN
BE EXPECTED. THE 12Z OPERATIONAL GFS IS QUITE COLD WITH 8H TEMPS
IN THE -17 TO -21 DEGREE RANGE ACROSS OUR AREA. THE GFSENSEMBLE
MEAN AND THE 12Z ECMWF ARE A COUPLE OF DEGREES WARMER BUT THE
TREND HAS BEEN COOLER OVER THE LAST FEW RUNS. THEREFORE...EXPECT A
SEASONABLY COLD DAY ON THURSDAY WITH HIGHS GENERALLY IN THE LOW TO
MID 20S.

THE SURFACE HIGH IS FORECAST TO SLIDE ACROSS THE TENNESSEE VALLEY 
THURSDAY NIGHT AND FRIDAY. THIS WILL LEAD TO DECREASING CLOUDS FROM 
THE SOUTH THURSDAY NIGHT AND WINDS SHOULD BEGIN TO DROP 
OFF...ESPECIALLY ACROSS OUR SOUTH. AS A RESULT...WILL GO AHEAD AND 
UNDERCUT GUIDANCE TEMPS SEVERAL DEGREES WITH LOWS GENERALLY IN THE 
10 TO 15 DEGREE RANGE. 

BELOW NORMAL TEMPERATURES WILL THEN CONTINUE THROUGH THE REST OF THE 
LONG TERM PERIOD AS BROAD UPPER LEVEL TROUGH REMAINS OVER THE 
NORTHEASTERN UNITED STATES THROUGH EARLY NEXT WEEK. MODELS ARE 
CONTINUING TO HINT AT SOME OVERRUNNING PCPN SPREADING UP INTO OUR 
AREA THIS WEEKEND. TIMING AND PLACEMENT IN THESE TYPES OF SITUATIONS 
ARE USUALLY DIFFICULT. HOWEVER...BOTH THE 12Z GFS AND ECMWF ARE IN 
PRETTY GOOD AGREEMENT BRINGING SOME LIGHT PCPN UP FROM THE 
SOUTH SATURDAY INTO SUNDAY. WILL THEREFORE GO AHEAD AND ALLOW FOR 
SOME 20-30 POPS DURING THAT PERIOD. AT THIS POINT...IT LOOKS LIKE 
TEMPS SHOULD BE COLD ENOUGH FOR BULK OF ANY PCPN TO REMAIN SNOW.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
EXPECT GENERALLY MVFR CIGS TO CONTINUE ACROSS THE TAF SITES THROUGH
MOST OF THE NIGHT. FCST SOUNDINGS SUGGEST A QUICK END TO THESE LOWER
CLDS EARLY TONIGHT BUT LOOKING AT SATELLITE AND UPSTREAM OBSERVATIONS
HAVE SLOWED DOWN IMPROVEMENT. PRECIPITATION TO OVERSPREAD THE TAF
SITES TUESDAY AHD OF A STRENGTHENING LOW PRESSURE SYSTEM THAT
WILL EJECT FROM THE CENTRAL PLAINS TUESDAY AFTN INTO THE MID MS
VALLEY BY LATE TUE EVENING. PRECIP MAY BEGIN AS A BRIEF WINTRY MIX
BEFORE CHANGING TO ALL RAIN TUE AFTN. EXPECT CIGS TO DROP BELOW
1000 FEET THRU THE AFTN INTO TUE EVENING.

WINDS WILL BE LIGHT AND VARIABLE TONIGHT AND THEN BECOME EASTERLY
BY TUE MORNING. EAST WINDS ON TUESDAY WILL INCREASE TO OVER 10
KNOTS WITH THE GREATEST IMPACT ON WENDESDAY WHEN THEY SHIFT TO THE
SOUTHWEST. 

OUTLOOK...WIDESPREAD PRECIPITATION WITH MVFR/IFR CIGS/VSBYS AND
GUSTY WINDS ARE LIKELY WEDNESDAY AND WEDNESDAY NIGHT. VERY STRONG
WINDS FROM THE SOUTHWEST ARE ALSO EXPECTED ON WEDNESDAY.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY 
     NIGHT FOR OHZ026-034-035-042>046-051>056-060>065-070>074-
     077>082-088.
KY...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY 
     NIGHT FOR KYZ089>100.
IN...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH LATE WEDNESDAY 
     NIGHT FOR INZ050-058-059-066-073>075-080.

&&

$$
SYNOPSIS...HAWBLITZEL
NEAR TERM...AR
SHORT TERM...HAWBLITZEL
LONG TERM...JGL
AVIATION...AR