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000
FXUS63 KJKL 212028
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
428 PM EDT TUE MAY 21 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 423 PM EDT TUE MAY 21 2013

THE AIR IS EXTREMELY UNSTABLE AND SO A SEVERE WEATHER WATCH WAS
ISSUED FOR ALL OF EASTERN KENTUCKY IN AN AREA. THE MAIN THREAT IS FOR
STRONG WINDS...HOWEVER HAIL CAN NOT BE TOTALLY RULED OUT AND WILL
LIKELY SEE AT LEAST SMALL HAIL IN THE AREA TODAY. WITH THE
POTENTIAL FOR SEVERE STORMS IN THE AREA...THE POSSIBILITY OF GUST
FRONTS WELL OUT AHEAD OF THE THUNDERSTORMS IS POSSIBLE. SEVERE WINDS
COULD ARRIVE WELL AHEAD OF THE PRECIPITATION. THE STORMS TO THE WEST
OF THE AREA HAVE HAD REPORTS OF SEVERE WIND...SO THIS THREAT IS REAL
AND IMMINENT. ONCE THIS LINE MOVES THROUGH THE AREA...THEN THERE
SHOULD BE A DECREASE IN ACTIVITY...AND THEN WILL INCREASE AGAIN ON
WEDNESDAY AND AN UPPER TROUGH MOVES ACROSS THE AREA. SOME OF THE
STORMS TOMORROW MAY BE STRONG AS WELL. FOR TEMPERATURES...USED A
BLEND OF THE NAM AND GFS MOS TO ADJUST THE PREVIOUS FORECAST. THE
WATCH IS VALID UNTIL 10 PM TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 347 PM EDT TUE MAY 21 2013

THE EXTENDED PERIOD OF THE FORECAST WILL FEATURE A PERIOD OF GOOD
MODEL AGREEMENT...AND A PERIOD OF POOR MODEL AGREEMENT. THE FIRST FEW
DAYS OF THE EXTENDED PERIOD WERE HANDLED VERY WELL BY BOTH THE GFS
AND ECMWF MODELS. SHOWERS AND STORMS WILL INCREASE IN COVERAGE DURING
THE DAY ON THURSDAY...BEFORE EXITING THE AREA THURSDAY NIGHT AND
FRIDAY...BEHIND A DEPARTING COLD FRONT. THE MODELS ALL AGREE THAT A
RIDGE OF HIGH PRESSURE WILL THEN SETTLE OVER THE AREA FRIDAY AND
SATURDAY...WHICH WILL MEAN COOLER AND DRIER WEATHER TO KICK OFF THE
UPCOMING WEEKEND. AFTER SATURDAY NIGHT...THINGS GET A BIT MURKY. THE
ECMWF MODEL IS MUCH WETTER AND MORE PROGRESSIVE THAN THE GFS
MODEL...BOTH IN THE TIMING OF A FRONTAL PASSAGE. THE ECMWF ACTUALLY
HAS PRECIPITATION AFFECTING EASTERN KENTUCKY FROM LATE SATURDAY
THROUGH TUESDAY. THE GFS...ON THE OTHER HAND...IS NOT MOVING PRECIP
INTO THE AREA UNTIL LATE SUNDAY NIGHT. FROM THEN ON THE MODELS DO
AGREE FAIRLY WELL...BUT ONLY FOR THE LAST DAY OR SO OF THE FORECAST
PERIOD. THAT BEING SAID...LEANED A BIT MORE TOWARD THE USUALLY MORE
RELIABLE ECMWF MODEL SOLUTIONS FROM EARLY SUNDAY ONWARD. DID NOT DO
A WHOLE LOT OF MAJOR CHANGING TO THE MODEL DATA BASED ON THE AMOUNT
OF UNCERTAINTY. THE MODEL SOUNDINGS WERE INDICATING ENOUGH INSTABILITY
TO PRODUCE THUNDERSTORMS...PARTICULARLY DURING THE AFTERNOON AND
EVENING PERIODS THURSDAY...SUNDAY...AND MONDAY. TEMPERATURES TO BEGIN
THE PERIOD WILL BE BELOW NORMAL FRIDAY AND SATURDAY...AS IT APPEARS A
COOL CANADIAN AIR MASS WILL SETTLE OVER THE AREA FOR A FEW DAYS. FROM
SUNDAY ONWARD...THINGS WILL WARM UP A BIT MORE DURING EACH DAYTIME
PERIOD...BUT NOT FAR FROM NORMAL VALUES FOR THIS TIME OF YEAR.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 135 PM EDT TUE MAY 21 2013

THE AIR IS EXTREMELY UNSTABLE AND THE STORM PREDICTION CENTER JUST
UPDATED THEIR OUTLOOK AND PUT EASTERN KENTUCKY IN AN AREA OF SLIGHT
RISK FOR SEVERE THUNDERSTORMS. THE MAIN THREAT IS FOR STRONG
WINDS...HOWEVER HAIL CAN NOT BE TOTALLY RULED OUT AND WILL LIKELY SEE
SMALL HAIL IN THE AREA TODAY. WITH THE POTENTIALLY SEVERE STORMS IN
THE AREA...THE POSSIBILITY OF GUST FRONTS WELL OUT AHEAD OF THE
THUNDERSTORMS IS POSSIBLE AND COULD CREATE SOME STRONG LLWS. CONFIDENCE
IN THE TIMING OF CONVECTIVE EVOLUTION IS NOT HIGH...AND WAS BASED ON
A COMBINATION OF THE NAM AND HIGH RESOLUTION RAPID REFRESH MODEL.
DEPENDING ON HOW MUCH RAIN OCCURS...THERE MAY BE A TIME OF POST
FRONTAL MIST WHICH WOULD LAST A FEW HOURS AND THEN IMPROVE. DUE TO
LOW CONFIDENCE ON TIMING AND EXTENT OF THE STORMS...THIS WAS NOT
ADDED TO THE TAFS. ALSO EXPECTING TO SEE SOME MIST AT THE TAF
STATIONS AND VALLEY FOG IN THE VALLEYS AND NEAR AREAS THAT GET A LOT
OF PRECIPITATION TODAY.


&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...JJ
LONG TERM...AR
AVIATION...JJ