FXUS61 KILN 080707
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
207 AM EST TUE DEC 8 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 THIS 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 THIS 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 TUESDAY/...
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 /07Z TUESDAY THROUGH SATURDAY/...
PLENTY OF CONCERNS FOR AVIATION THROUGH THE NEXT TAF CYCLE AND
BEYOND. CURRENT ISSUE IS MVFR CIGS WHICH HAVE BEEN SLOW TO
ERODE...WITH POOR MODEL RESOLUTION OF THE THIN LAYER OF MOISTURE
AROUND 2500FT ACROSS THE AREA. CLEARING HAS BEEN WORKING SOUTH
TOWARD THE TAF SITES FROM NRN OHIO WITH WEAK SUBSIDENCE...BUT
WINDOW OF OPPORTUNITY IS GETTING SMALLER WITH EAST/SOUTHEAST WINDS
SET TO PICK UP AFTER 12Z...WHICH MAY HINDER ANY FURTHER EROSION.
WILL CONTINUE TO DELAY THE DISSIPATION OF THE CLOUDS PER SATELLITE
TRENDS...AND CONTINUE THE MVFR CIGS/VSBYS THROUGH THE REST OF THE
NIGHT.
EXPECT POTENT MIDWEST STORM TO SPREAD PRECIPITATION OVER THE TAF
SITES AS EARLY AS 19Z /CVG/ AND 22Z /CMH/...AND ONSET OF PCPN
COULD BE A MIX OF SNOW/SLEET/RAIN AT ALL OF THE TAF SITES EXCEPT
CVG WHICH SEEMS TO ENTRENCHED IN THE WARMER AIR. COULD SEE A
BURST OF HEAVIER MIXED PRECIPITATION BEFORE INCREASING SOUTHERLY
FLOW CHANGES EVERYTHING OVER TO RAIN BY THIS EVENING...WITH
CIGS/VSBYS TANKING TO IFR WITH THE HEAVIER PRECIPITATION. THIS
BRIEF WINDOW OF MIX COULD POSE PROBLEMS AT CMH/DAY/LCK/ILN AND
WILL CONTINUE TO ASSESS THIS FOR THE 12Z TAF.
ONCE CHANGE TO RAIN OCCURS THIS EVENING...SHOULD REMAIN AT IFR AT
MOST LOCATIONS THROUGH THE NIGHT WITH CONTINUED RAIN/FOG. THEN ALL
EYES ON STRONG WIND LIKELIHOOD AS STRONG COLD FRONT PLOWS THROUGH
ON WED MORNING. ONCE WINDS SWITCH TO SWLY...WILL SEE SUSTAINED
25-35KT ALL SITES WITH GUSTS TO 50KT POSSIBLE FOR MUCH OF THE DAY.
VERY STEEP/UNSTABLE LOW LEVEL LAPSE RATES...WILL BE OFFSET BY
AMPLE LOW CLOUDS AND RATHER STRONG LIFT IN THE LOWEST 2KM. A GOOD
THING AS OTHERWISE THE POTENTIAL TO MIX DAMAGING GUSTS TO THE
SURFACE WOULD BE MUCH HIGHER.
OUTLOOK...WIDESPREAD MVFR/IFR CIGS AND STRONG WINDS ARE LIKELY
WEDNESDAY NIGHT. MORE IFR/MVFR CIGS AND PRECIPITATION POSSIBLE
SATURDAY.
&&
.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...BINAU
