FXUS63 KJKL 082339
AFDJKL
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
639 PM EST TUE DEC 8 2009
.SHORT TERM.../TONIGHT THROUGH WEDNESDAY NIGHT/
LOW PRESSURE CONTINUES TO ORGANIZE OVER THE SOUTHERN PLAINS WITH
RAIN AND A FEW EMBEDDED THUNDERSTORMS QUICKLY SPREADING
NORTHEASTWARD INTO THE OHIO VALLEY. THE LOW WILL STRENGTHEN RAPIDLY
TONIGHT AS IT HEADS TO THE GREAT LAKES REGION BY WEDNESDAY MORNING.
A COLD FRONT WILL RACE ACROSS OUR AREA TOWARDS DAWN ON WEDNESDAY
WITH A MUCH COLDER AIR MASS EXPECTED BEHIND THE FRONT LATE WEDNESDAY
INTO WEDNESDAY NIGHT.
FORECAST MODELS ARE HANDLING THIS EVENT FAIRLY CONSISTENTLY WITH NO
SURPRISES NOTED IN THE 08/12Z RUNS. INHERITED FORECAST WAS TWEAKED
ONLY SLIGHTLY THROUGH THE PERIOD USING MAINLY THE 08/12Z NAM.
EXPECTED STORM IMPACTS ON EASTERN KENTUCKY INCLUDE:
- HEAVY RAINFALL... STRONG LOW LEVEL JET PUNCHING NORTHWARD AND
RESULTING ISENTROPIC LIFT THIS EVENING WILL BRING A PROLONGED PERIOD
OF MODERATE TO HEAVY RAINFALL TO THE AREA TONIGHT. PWATS INCREASE TO
TO WELL OVER AN INCH AND THE MODEL CONSENSUS OF FROM BETWEEN 1.00
AND 1.5 INCHES OF RAINFALL SEEMS REASONABLE AND WAS ACCEPTED. SOME
MINOR FLOODING OF URBAN AND LOW-LYING AREAS MAY TAKE PLACE... AND
HEIDELBERG AND RAVENNA ARE FORECAST TO REACH ACTION STAGE AS THIS
WATER DRAINS AWAY LATER WEDNESDAY INTO THURSDAY... BUT NO MAJOR
FLOODING PROBLEMS ARE EXPECTED WITH THIS AMOUNT OF RAINFALL.
- DAMAGING WINDS... TWO MAIN CONCERNS HERE. FIRST IS WITH ANY
POTENTIAL LOW-TOPPED CONVECTION THAT COULD FORM WITH THE FRONT AS IT
PASSES THROUGH NEAR DAWN ON WEDNESDAY. MARGINAL ELEVATED INSTABILITY
WILL EXIST OVER OUR AREA LATER TONIGHT BASED ON PROGS. THE LOW LEVEL
JET COINCIDENT WITH THE FRONT WILL BE IN EXCESS OF 60 KTS SO A BRIEF
PERIOD OF VERY STRONG WINDS WILL BE LIKELY AS THE FRONT AND ANY
ASSOCIATED CONVECTION... WHETHER OR NOT IT CONTAINS THUNDER... MOVES
THROUGH.
AS THE DRY SLOT THEN SHIFTS OVERHEAD BEHIND THE FRONT WEDNESDAY
MORNING INTO THE EARLY AFTERNOON HOURS... WE SHOULD MIX INTO THE VERY
STRONG LOW LEVEL JET. BUFKIT SOUNDINGS INDICATE A STRONG POTENTIAL
FOR 50-KT GUSTS FROM ROUGHLY 8 AM UNTIL 2 PM OR SO. AS STATED IN AN
EARLIER DISCUSSION... THIS SYSTEM BEARS SOME SIMILARITY TO A FEB 2009
SYSTEM WHICH PRODUCED UP TO 60 MPH POST-FRONTAL WINDS. SATURATED SOIL
FROM THE RAIN THIS AFTERNOON AND TONIGHT SHOULD MEAN A LOT OF TREE
DAMAGE FROM WINDS OF THIS MAGNITUDE.
WITH ALL THAT BEING SAID... WE WILL UPGRADE OUR HIGH WIND WATCH TO A
HIGH WIND WARNING FOR THE ENTIRE FORECAST AREA... AND RUN IT FROM 4
AM UNTIL 10 PM WEDNESDAY. DO NOT ANTICIPATE WARNING LEVEL WINDS
THROUGH THE ENTIRE PERIOD... BUT LATER SHIFTS CAN DOWNGRADE TO AN
ADVISORY ONCE THE WINDS SUBSIDE ENOUGH... WHICH THEY SHOULD DO
DURING THE LATE AFTERNOON HOURS.
ALSO... GAVE SOME THOUGHT TO THE POSSIBILITY OF AN EARLIER ADVISORY
OR WARNING FOR OUR VIRGINIA BORDER COUNTIES. HOWEVER... A STABLE NEAR
SURFACE LAYER IN ADVANCE OF THE FRONT SHOULD KEEP THE 60-KT PLUS LOW
LEVEL JET FROM BEING REALIZED AT THE SURFACE... PLUS THE LOW LEVEL
WIND DIRECTION AT MOUNTAIN TOP LEVEL IS EXPECTED TO BE A LITTLE TOO
SOUTHERLY FOR MOUNTAIN WAVE GENERATION ON THE WINDWARD SIDE OF BLACK
MOUNTAIN.
- FALLING TEMPERATURES AND SNOW THREAT WEDNESDAY/WEDNESDAY NIGHT...
MUCH COLDER AIR WILL WRAP AROUND THE SYSTEM ON WEDNESDAY WITH
TEMPERATURES PLUMMETING INTO THE 30S BY LATE IN THE AFTERNOON. WRAP
AROUND MOISTURE LOOKS DEEP ENOUGH THAT A FEW RAIN SHOWERS MAY BE
SQUEEZED OUT... TURNING TO SNOW SHOWERS BY LATE IN THE AFTERNOON.
ISOLATED TO WIDELY SCATTERED SNOW SHOWERS WILL THEN CONTINUE
WEDNESDAY NIGHT AS TEMPERATURES LOWER INTO THE 20S. A LIGHT DUSTING
IS POSSIBLE... MAINLY ALONG AND TO THE EAST OF THE ESCARPMENT/DANIEL
BOONE NATIONAL FOREST. THE CONTINUING GUSTY WINDS WILL BRING REDUCED
WIND CHILLS INTO THE SINGLE DIGITS AND TEENS BY THURSDAY MORNING.
.LONG TERM.../THURSDAY THROUGH TUESDAY/
LONGWAVE PATTERN TO BE MAINLY ZONAL ACROSS CONUS THIS PERIOD WITH
MAJOR TROUGHS OVER ATLANTIC/PACIFIC. SHORTWAVES AGAIN ARE HARD TO
TIME BUT MODELS AGREE IN ANOTHER SYSTEM BRUSHING EAST KY ON SAT WITH
SOME SNOW...SIMILAR TO LAST SAT EXCEPT MODELS THIS TIME ACTUALLY
PAINT SOME QPF OVER THE AREA. GFS LOOKS OVERDONE WITH QPF WITH ITS
0.5 INCH. IT MOISTENS THE BOUNDARY LAYER TOO QUICKLY THOUGH THE
ISENTROPIC LIFT (295K SURFACE) SO FAR LOOKS DECENT.
FARTHER OUT...MODELS AND ASSOCIATED ENSEMBLES SHOW FAIR AGREEMENT IN
A SYSTEM BEING IN THE VICINITY BY TUE OR TUE NIGHT BUT CANNOT SEE
ANY DETAIL. TEMPERATURES WILL REMAIN BELOW SEASONAL LEVELS BUT
ENSEMBLES SHOW SIGNIFICANT SPREAD BY EARLY NEXT WEEK.
&&
.AVIATION.../00Z TO 24Z/...UPDATED
CONDITIONS HAVE BEEN IFR OR WORSE OVER THE PAST SEVERAL HOURS AT THE
TAF SITES... HOWEVER EXPECT A BIT OF AN IMPROVEMENT TO THE IFR/MVFR
THRESHOLD FOR THE NEXT SEVERAL HOURS AS STRENGTHENING DOWNSLOPE WINDS
KEEP THE LOWEST LEVELS A LITTLE MIXED. NEVERTHELESS... EXPECT IFR OR
WORSE CONDITIONS IN HEAVY RAIN AT TIMES AND INCREASING SOUTHERLY
SURFACE WINDS AS THE POWERFUL COLD FRONT APPROACHES OVERNIGHT. A LINE
OF SHOWERS AND PERHAPS A THUNDERSTORM WILL THEN ACCOMPANY THE INTENSE
COLD FRONT AS IT RACES ACROSS EAST KENTUCKY LATE TONIGHT/EARLY
WEDNESDAY MORNING. STRONG VARIABLE WIND GUSTS TO 45 KTS OR MORE WILL
BE POSSIBLE WITH THESE SHOWERS OR STORMS... AND STRONG POST-FRONTAL
WINDS FROM THE SOUTHWEST GUSTING UP TO 50 KTS OR MORE ARE EXPECTED
BEHIND THE FRONT THROUGH THE END OF THE PERIOD. POST FRONTAL CLOUDS
COULD SCATTER A BIT AND VFR VIS/CIGS WILL BE POSSIBLE FOR A BRIEF
PERIOD OF TIME... HOWEVER WEST SOUTHWEST WINDS OF 30 TO 35 MPH AND
GUSTS UP TO 60 MPH WILL MAKE IT NEARLY IMPOSSIBLE FOR ANY SMALL
AIRCRAFT TO FLY. EXPECT A STRATOCU DECK AROUND THE VFR/MVFR
THRESHOLD TO BUILD BACK IN LATE WEDNESDAY AFTERNOON AND EVENING WITH
LINGERING RAIN AND SNOW SHOWERS POSSIBLE.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING FROM 4 AM TO 10 PM EST WEDNESDAY FOR KYZ044-
050>052-058>060-068-069-079-080-083>088-104-106>120.
&&
$$
SHORT TERM...ABE
LONG TERM....GV
AVIATION...SCHOETTMER
