000
FXUS63 KJKL 032000
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
300 PM EST WED DEC 3 2008
.SHORT TERM.../TONIGHT THROUGH THURSDAY NIGHT/...UPDATED
THE TIMING OF THE MODELS FOR THIS NEXT SYSTEM IS A BIT SLOWER THAN
THE PREVIOUS RUNS EXCEPT FOR THE NAM WHICH HAS BEEN CONSISTENTLY
SLOWER THAN THE OTHER TWO. THE DILEMMA FOR THIS FORECAST IS WHETHER TO
BELIEVE THE NAM OR THE GFS. THE GFS HAS THE OMEGA MOSTLY AHEAD OF AND
WITH THE FRONT...WHEREAS THE NAM HAS A SIGNIFICANT AREA OF MID LEVEL
OMEGA BEHIND THE FRONT. WITH THE NAM SOLUTION...THE BUFR SOUNDINGS
ARE CLEARLY SHOWING SNOW BEHIND THE FRONT. THE OMEGA IS MOST LIKELY
FROM THE RIGHT ENTRANCE REGION OF THE JET. SINCE THE NAM HAS BEEN
MORE CONSISTENT WITH THIS SYSTEM...WENT WITH THE NAM SOLUTION AND PUT
IN A MIX OF RAIN AND SNOW BEHIND THE FRONT. WITH THE WARM SURFACE
TEMPERATURES...I DO NOT EXPECT ANY ACCUMULATION...EXCEPT MAYBE ABOVE
2500 FEET ALONG THE VA BORDER WHICH MAY PICK UP AN INCH. AN OUTLIER
SOLUTION WOULD BE FOR SOME OF THE SHELTERED VALLEYS TO DECOUPLE
TONIGHT AND GET SOME FREEZING RAIN NEAR DAWN. I HAVE DISCOUNTED THIS
SOLUTION BECAUSE THE WINDS WILL BE TOO STRONG AND SHOULD MIX OUT THE
TEMPS AND NOT LET THEM GET BELOW FREEZING. I WOULD NOT BE TOO
SURPRISED TO SEE SOME SLEET MIXED IN WITH THE RAIN AROUND 8 AM
TOMORROW.
.LONG TERM.../FRIDAY THROUGH WEDNESDAY/...UPDATED
QUITE A BIT OF MID AND HIGH LEVEL CLOUDINESS LIKELY ON FRIDAY
KEEPING TEMPS CHILLY AS UPPER LEVEL TROUGH BEGINS TO DIVE INTO THE
EAST. STRONG SHORT WAVE WILL THEN DROP INTO THE OHIO VALLEY ON
SATURDAY. BEST MOISTURE AND DYNAMICS ARRIVE LATE IN THE DAY WITH
UPSLOPE FLOW DEVELOPING OVERNIGHT. THIS SHOULD RESULT IN AN INCREASE
IN SNOW SHOWER LATE IN THE AFTERNOON AND THROUGH THE NIGHT. BOUNDARY
LAYER MAY BE WARM ENOUGH FOR A RAIN/SNOW MIX WITH ANY SHOWER
ACTIVITY DURING THE DAY... BUT COLUMN WILL COOL QUICKLY SUPPORTING
ALL SNOW OVERNIGHT WITH SOME LIGHT ACCUMULATIONS POSSIBLE IN THE
FAVORED HIGHER TERRAIN OF SOUTHEAST KENTUCKY.
ANY SNOW SHOWER ACTIVITY SHOULD TAPER OFF QUICKLY SUNDAY MORNING AS
THE UPPER TROUGH SHIFTS EAST AWAY FROM THE REGION AND HIGH PRESSURE
BUILDS IN AT THE SURFACE. DROPPED TEMPS A FEW DEGREES ON SUNDAY WITH
PROGGED 850 MB AIRMASS OVERHEAD LIKELY ONLY SUPPORTING MID 30S AT
BEST.
HIGH PRESSURE WITH RISING HEIGHTS ALOFT SHOULD SUPPORT A MODEST WARM
UP ON MONDAY WITH TEMPS WARMING INTO THE LOW TO MID 40S.
MODELS THEN INDICATE A SHORTWAVE WILL DIVE SOUTHEAST THROUGH THE
PLAINS SUPPORTING CYCLOGENESIS TO OUR WEST MONDAY NIGHT. IT APPEARS
LIKE THE BEST TIME FRAME FOR PRECIP ACROSS THE AREA IS ON TUESDAY
INTO TUESDAY NIGHT BASED LARGELY ON THE 03/12Z GFS AND NCEP
ENSEMBLE. 03/12Z ECMWF IS MUCH QUICKER WITH THE SYSTEM MOVING ANY
PRECIP OUT QUICKLY TUESDAY NIGHT. WILL CONTINUE WITH CHANCE POPS
ONLY TUESDAY THROUGH WEDNESDAY DUE TO THE UNCERTAINTY AND MENTION
ONLY RAIN UNTIL TUESDAY NIGHT WHEN THERE IS SUPPORT FOR A POSSIBLE
RAIN/SNOW CHANGEOVER WITH RAIN AND SNOW MIX POSSIBLE THROUGH THE DAY
ON WEDNESDAY.
&&
.AVIATION.../18Z TO 18Z/
HIGH PRESSURE OVER THE SOUTHEASTERN UNITED STATES WILL KEEP VFR
CONDITIONS WITH SOME CI OVER THE AREA TODAY. STRONGER WINDS ALOFT
WILL EVENTUALLY MIX DOWN TO PRODUCE GUSTS NEAR 20 KT FROM THE SOUTH
THIS AFTERNOON. LOW LEVEL JET RAMPS UP THIS EVENING AHEAD OF AN
APPROACHING COLD FRONT. AS SURFACE GUSTS DISSIPATE SOME...SO WILL
LEAVE THE MENTION OF WIND SHEAR IN BEGINNING AROUND 01Z. SHOULD SE
SSW WINDS 45 KT AT 1500 FT...WITH THE SHEAR LAYER DEEPENING TO
AROUND 2000 FT WITH SPEEDS INCREASING TO 50 KT AROUND 05Z. BKN CI
WILL GIVE WAY TO BKN SC AROUND 5 KFT TOWARD 05Z AS WELL. COULD BE
SOME SPRINKLES AHEAD OF THE FRONT...BUT WILL BRING IN THE BULK OF
THE PRECIP AFTER 9Z AT THE TAF SITES. WINDS ALOFT SHOULD RELAX
SOME...WITH SOME OF THE WINDS MIXING DOWN TO THE SURFACE AGAIN AFTER
08Z. FROPA SHOULD OCCUR AT SME AROUND 13Z AND AT JACKSON AND LONDON
BY 14Z. THERE IS A BIG DIFFERENCE IN THE MODELS AS TO WHAT HAPPENS
AFTER THE FROPA. THE NAM IS SHOWING A LARGE AREA OF UPWARD VERTICAL
MOTION BEHIND THE FRONT WHICH COULD PRODUCE IFR TO VLIFR SNOW.
ALTHOUGH IT WOULD NOT STICK TO THE GROUND...IT COULD REALLY LOWER
THE VISIBILITIES SIGNIFICANTLY. RIGHT NOW...WILL PUT SOME PROB30
SNOW IN THE FORECAST.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...JJ
LONG TERM...ABE
AVIATION...JJ
