FXUS63 KJKL 250101
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
800 PM EST THU DEC 24 2009

.SHORT TERM.../EARLY THIS EVENING/...UPDATED

A BAND OF LIGHT RAIN IS CURRENTLY LIFTING NORTHEAST ACROSS THE AREA.
MOST OF THIS IS PRODUCING UP TO 5 HUNDREDTHS OF AN INCH OVER A GIVEN
LOCATION. LOW LEVEL JET IS RAMPING UP QUICKLY AS SCHEDULED...WITH OHX 
COMING IN WITH 70 KTS AT 850 MB. THIS IS ACTUALLY A BIT STRONGER THAN
EITHER THE 18Z WRF OR GFS HAD FORECAST...ALTHOUGH IT IS HARD TO
TELL IF THEY ARE UNDERDONE...OR JUST A BIT SLOW WITH SHIFTING THE
SWATH OF HIGHER SPEEDS TO THE EAST. SOME STRONGER WINDS ARE BEING
NOTED OUT IN CENTRAL KENTUCKY...WITH SOME GUSTS AROUND 45 MPH AND
SUSTAINED WIND SPEEDS OF 30 MPH AT A FEW LOCATIONS. STILL BELIEVE
THAT 40 MPH FOR THE GUSTS AND 25 MPH FOR THE SUSTAINED WILL HOLD AT
MOST LOCATIONS HERE...SO WILL KEEP THE LAKE WIND ADVISORY GOING.

THE MAIN REASON FOR THIS EARLY EVENING UPDATE IS SOME OF THE LOW
TEMPERATURES. DESPITE THICK MID-LEVEL CLOUD COVER OVERHEAD...THE
COOLER SHELTERED VALLEYS IN THE EAST HAVE GOTTEN DOWN INTO THE
MIDDLE AND UPPER 30S ALREADY. THESE WILL JUMP UP QUICKLY INTO THE
OVERNIGHT HOURS...ONCE THE GRADIENT SHARPENS. 

WILL ADDRESS THE POTENTIAL NEED FOR A HIGH WIND WARNING IN THE
SOUTHEASTERN TERRAIN A BIT LATER THIS EVENING. UPDATE OUT SHORTLY.

THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS...

/TONIGHT THROUGH SATURDAY/

19Z SFC ANALYSIS SHOWS A DEEP AND QUITE LARGE AREA OF LOW PRESSURE
COVERING THE MISSISSIPPI VALLEY...MUCH OF THE MIDWEST...AND BULGING
EAST INTO THE OHIO VALLEY. A WARM FRONT FROM THIS HAS SET UP JUST
NORTH OF JACKSON. TO THE SOUTH OF THIS BOUNDARY...SOUTHEAST WINDS ARE
SENDING TEMPERATURES UP INTO THE MIDDLE AND UPPER 50S WHILE UPPER 40S
AND LOWER 50S ARE FOUND TO THE NORTH. EVEN BLACK MOUNTAIN...WHERE
THERE IS LIKELY STILL A HALF FOOT OF SNOW ON THE GROUND IS REPORTING
A RELATIVELY BALMY 47 DEGREES. JUST A FEW LIGHT SHOWERS ARE FOUND
ALONG THIS FRONTAL BOUNDARY...BUT MORE SUBSTANTIAL RAINS ARE SEEPING
NORTH INTO THE FRINGES OF THE SOUTHERN APPALACHIANS ON THIS ADVECTION.
ADDITIONAL...HEAVIER RAINS ARE CURVING NORTHEAST ALONG THE SYSTEM/S
COLD/OCCLUDED FRONT SWEEPING INTO THE DEEP SOUTH...BOUND FOR THE
TENNESSEE VALLEY. DESPITE THE SPECKS OF MELTING SNOW ACROSS THE
AREA...DEWPOINTS HAVE FALLEN THIS AFTERNOON INTO THE UPPER 20S IN
THE SOUTH AND INTO THE LOWER 30S NORTH. THIS DRIER AIR WILL LIKELY
CONTINUE TO SLOW THE ARRIVAL OF SHOWERS INTO THE CWA LATE THIS
AFTERNOON AND WELL INTO THE EVENING. WINDS HAVE ONLY SLOWLY PICKED UP
THROUGH EAST KENTUCKY...BUT WILL LIKELY START GUSTING INTO THE 20 TO
30 MPH RANGE OVER THE NEXT FEW HOURS...THEY ALREADY HAVE OVER
POTIONS OF WESTERN KENTUCKY...AS THE PRESSURE GRADIENT REALLY STARTS
TO TIGHTEN.

THE MODELS HAVE STARTED TO COME INTO BETTER AGREEMENT ALOFT WITH THE
MUCH ANTICIPATED PATTERN EVOLUTION. TWIN SHORT WAVES...ONE
APPROACHING ARKLATEX FROM THE WEST AND ANOTHER COMING SOUTH OUT OF
EASTERN MONTANA...WILL PINWHEEL...FUJIWARA STYLE...INTO EACH OTHER
TO FORM A LARGE LOW OVER THE CENTER OF THE COUNTRY BY 00Z SATURDAY.
THIS METEOROLOGICAL DANCE...THE SPECIFICS OF WHICH ARE BOUND TO BE
ILL HANDLED BY ANY MODEL...WILL ADD A DEGREE OF UNCERTAINTY TO THE
WEATHER SPECIFICS NEAR THE LOW/S CENTER. AS SUCH...HAVE FOLLOWED A
BLEND OF THE GFS AND ECMWF...BOTH OF WHICH SET UP THE LOW FURTHER
EAST THAN THE NAM FRIDAY EVENING. THEY ALSO AGREE ON SWEEPING THE
SHORTWAVE ENERGY INTO EAST KENTUCKY LATE TONIGHT AND THROUGH US BY
MIDDAY FRIDAY. THE SOLUTIONS BETTER CLUSTER ON SATURDAY AS THE CENTER
OF THE UPPER LOW SLOWLY WHIRLS INTO CHICAGO-LAND...IN THE PROCESS
EASING A VORT STREAM DEEPER INTO KENTUCKY. WITH THE DECENT ENOUGH
AGREEMENT HAVE ALSO FOLLOWED THE GFS AND ECMWF CLOSEST FOR THE
WEATHER DETAILS THROUGH SATURDAY.

SENSIBLE WEATHER WILL FEATURE A QUITE ACTIVE 24 TO 36 HOURS OF
WEATHER ACROSS EAST KENTUCKY. AFTER A SLOW START...A FEW STRAY
SHOWERS WILL CREEP INTO OUR AREA EARLY THIS EVENING WITH THE MAIN
RAIN BAND SET TO ARRIVE TOWARD MIDNIGHT PUSHING EAST THROUGH THE REST
OF THE NIGHT AND INTO EARLY FRIDAY MORNING. THE WINDS WILL LIKEWISE
MAKE UP FOR LOST TIME THIS EVENING...QUICKLY BECOMING GUSTY THROUGH
THE ENTIRE AREA...NECESSITATING A LAKE WIND ADVISORY. THESE 30 TO 40
MPH GUSTS WILL SEEM TAME COMPARED TO THE POTENTIAL ALONG OUR HIGHEST
PEAKS IN THE EAST AS AN 80 TO 85 KT 850 MB JET CROSSES THE RIDGE
ORIENTATION AT A SHARP ANGLE. IN THE PAST...THIS SCENARIO HAS SHOWN
THE CAPABILITY TO GENERATE MOUNTAIN WAVES AND THEREBY BRING DAMAGING
WIND GUSTS TO THE SFC IN THE VICINITY OF THE HIGHEST PEAKS NEAR THE
VIRGINIA BORDER. AT THIS POINT...THOUGH...WILL HANDLE THIS
DEVELOPING THREAT WITH THE CURRENT WIND ADVISORY AND RECOMMEND TO THE
LATER SHIFTS AN UPGRADE TO SHORT FUSE HIGH WIND WARNINGS SHOULD
INDICATIONS OF HIGHER WINDS DESCENDING TO THE SFC BEGIN TO MANIFEST.
OUR LAKE WIND ADVISORY...PERHAPS MORE PERTINENT THAN NORMAL FOR LATE
DECEMBER FOLLOWING A DAY WHERE 60 DEGREES WAS LIKELY REACHED ON LAKE
CUMBERLAND...WILL COVER THE OTHER WINDS FOR THE REST OF THE AREA
THROUGH FRIDAY AFTERNOON. 

THE RAIN BAND ASSOCIATED WITH THE FRONT WILL BE ENHANCED BY PLENTY
OF UPPER LEVEL DIVERGENCE ON THE NOSE OF A 125 KT 300 MB JET STREAK
ARCING INTO SOUTHEAST KENTUCKY LATE TONIGHT. HOWEVER...THE
PROGRESSIVE NATURE OF THE FRONT WILL LIMIT THE RAINFALL POTENTIAL TO
SOMEWHERE BETWEEN A QUARTER AND A HALF AN INCH. AFTER THE MELTING OF
THE PAST SEVERAL DAYS...DOUBT THAT THE LIQUID EQUIVALENT OF ANY OF
THE REMAINING SNOW PACK IS ABOVE A HALF AN INCH. THEREFORE...THE
CONCERN FOR FLOODING...FLASH OR OTHERWISE...HAS EASED SOMEWHAT.

COLDER AIR DOES TRY TO POUR INTO THE STATE ON FRIDAY...BUT WITH
SOUTHWEST WINDS AROUND A MATURE SYSTEM AND EVEN SOME RETURNING
SUNSHINE POSSIBLE IN THE DRY SLOT TOMORROW...EXPECT THE CHILL TO BE
BLUNTED. COLDER AIR MAKES A BETTER PUSH EAST FRIDAY NIGHT WHICH WILL
ALSO HELP TO MIX AND CHANGE ANY LINGERING SHOWERS TO SNOW. THE SNOW
THREAT BEHIND THE FRONT AND THROUGH SATURDAY MORNING WILL BE
UNUSUALLY LOW FOR THE WAKE OF A STRONG FROPA IN THE WINTER AS THE
WIND FLOW WILL REMAIN UNFAVORABLE FOR UPSLOPE AND THE WRAP AROUND
MOISTURE FROM THE PARENT LOW WILL HOVER WELL TO THE NORTHWEST. THIS
AREA OF SCATTERED LIGHT SNOW AND THE PASSING UPPER LOW WILL SNEAK
BACK TOWARD THE CWA LATER SATURDAY AND SMALL CHANCES HAVE BEEN
INCLUDED FOR THIS.

AS FOR TEMPERATURES...GENERALLY BLENDED CURRENT CONDITIONS INTO THE
RAW NUMBERS FROM THE NAM ALONG WITH ITS DIURNAL CURVE THROUGH FRIDAY.
FOLLOWING THAT...UNDER CUT THE GUIDANCE FOR FRIDAY NIGHT AND ALSO THE
COLDER MAV NUMBERS FOR HIGHS SATURDAY. WITH THE POPS...DESPITE THE
PREFERENCE FOR THE GFS SOLUTION...THE MET NUMBERS MATCHED UP BEST
WITH OUR FORECAST THROUGH THE SHORT TERM. 

.LONG TERM.../SATURDAY NIGHT THROUGH THURSDAY/

AN IMPRESSIVE PAIR OF DUMB BELLING LOWS WILL FINALLY SWING THROUGH 
THE OHIO VALLEY FOR THE LAST TIME BY THE END OF THE WEEKEND. LOW 
LEVEL FLOW TO TURN WEAKLY UPSLOPE ON SUNDAY ALONG WITH A LITTLE 
BETTER MOISTURE THAN PREVIOUSLY EXPECTED. THIS SHOULD NOT RESULT IN 
SIGNIFICANT SNOW AND KEPT PROBABILITY AS A CHANCE THOUGH DID RAISE 
IT SOME. BEST CHANCE OF MEASURABLE SNOW WILL BE SUNDAY BEFORE THE 
UPPER TROUGH PASSES BY. 
   
LONGWAVE PATTERN TO BECOME SLIGHTLY PROGRESSIVE NEXT WEEK WHILE 
CONUS TRANSITIONS TO ZONAL FLOW...AT LEAST TEMPORARILY...WITH A 
DOMINANT SOUTHERN STREAM. GFS AND ECMWF DIFFER SIGNIFICANTLY ON NEXT 
SYSTEM EXPECTED TO ARRIVE ABOUT NEW YEARS EVE. ECMWF SHOWS A MORE 
AMPLIFIED TROUGH AND THUS DRAWS GULF MOISTURE AND WARM AIR FARTHER 
NORTH THAN DOES GFS. ECMWF HAS PERFORMED BETTER OF LATE BUT IS TOO 
EARLY TO JUMP WITH BOTH FEET.

&&

.AVIATION.../00Z TO 24Z/

WINDS AND WIND SHEAR THE MAIN AVIATION FORECAST CONCERNS THIS TAF
PERIOD...THOUGH SOME SHOWERS WITH NEAR MVFR CIGS WILL OCCUR ACROSS
THE REGION DURING THE TAF PERIOD AS WELL. LOW LEVEL WIND SHEAR ON 
THE ORDER OF 50KTS OR GREATER TO MOVE INTO THE REGION AFTER 03Z AND
REMAIN THROUGH AROUND 10Z OR SO. DURING THIS TIME...SURFACE WINDS
WILL INCREASE AS WELL THOUGH THESE SHOULD PEAK OUT IN THE 10-15KT
SUSTAINED WITH GUSTS UP TO 25KTS. WINDS SHOULD REMAIN GUSTY THROUGH
AT LEAST 18Z FRIDAY. 

RAIN SHOWERS WILL BRING CEILINGS DOWN TO LOW VFW AND MAY CROSS INTO
MVFR AT TIMES AFTER 12Z...BUT CONFIDENCE IN THIS IS TOO LOW TO
INCLUDE IN THE TAFS AT THIS TIME. RAIN SHOULD NOT REDUCE VISIBILITIES
TO ANYTHING LESS THAN LOW VFR SO WILL NOT INCLUDE MENTION OF LOWER
VIS IN THE TAFS AT THIS TIME. 

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 4 PM EST FRIDAY FOR KYZ044-050>052-
058>060-068-069-079-080-083>086-104-106>117-119.

WIND ADVISORY UNTIL 4 PM EST FRIDAY FOR KYZ087-088-118-120.

&&

$$

SHORT TERM...GREIF/GEOGERIAN
LONG TERM....GV
AVIATION...MACZKO