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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KJKL 220602 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
202 AM EDT WED MAY 22 2013

.UPDATE...
-- Changed Discussion --
ISSUED AT 155 AM EDT WED MAY 22 2013

HOURLY TEMP...DEWPOINT AND SKY GRIDS WERE FRESHENED UP A BIT BASED ON
RECENT OBS AND SATELLITE IMAGERY. AN OUTFLOW BOUNDARY IS WORKING ITS
WAY INTO THE LAKE CUMBERLAND REGION. EAST KY IS GENERALLY WORKED OVER
FROM EARLIER CONVECTION. HOWEVER...ISOLATED TO SCATTERED SHOWERS AND
POSSIBLY A THUNDERSTORM CANNOT BE RULED OUT IN THE WESTERN CWA
OVERNIGHT AS THIS WORKS IN. PATCHY FOG SHOULD CONTINUE TO FORM
ACROSS THE REGION...ESPECIALLY IN THE VALLEYS.

UPDATE ISSUED AT 1115 PM EDT TUE MAY 21 2013

DID AN OVERNIGHT UPDATE TO BETTER TIME THE NEXT BATCH OF SHOWERS AND
ISOLATED THUNDERSTORMS INTO THE AREA LATER TONIGHT. EXPECT THE
MESOSCALE FEATURE RESPONSIBLE FOR THE CURRENT CONVECTION TO THE WEST
TO FURTHER WEAKEN AS IT COMES EAST AND ENCOUNTERS OUR RAIN COOLED
AIR. HOWEVER...THERE WILL LIKELY BE ENOUGH LIFT LEFT WITH THIS TO
KEEP A SMALL CHANCE OF SHOWERS OR AN ISOLATED THUNDERSTORM IN THE
FORECAST THROUGH DAWN. HAVE ALSO ADDED SOME PATCHY FOG TO THE HILLS
EARLY THIS NIGHT AND IN THE VALLEYS TOWARD DAWN. OTHERWISE...JUST
MATCHED UP THE CURRENT OBS AND TREND TO THE T AND TD GRIDS. UPDATES
HAVE BEEN SENT TO THE NDFD AND WEB SERVERS ALONG WITH THE HWO AND
ZFP.

UPDATE ISSUED AT 905 PM EDT TUE MAY 21 2013

UPDATED THE FORECAST TO REFLECT CURRENT CONDITIONS AND MODEL TRENDS.
THE LINE OF STORMS HAS MOVED OUT OF EASTERN KENTUCKY INTO WEST
VIRGINIA. WIDESPREAD DAMAGE WAS REPORTED ACROSS EASTERN KENTUCKY FROM
LATE THIS AFTERNOON TO 8 PM. THE BIG QUESTION NOW IS WHAT THE SQUALL
LINE OVER WESTERN KENTUCKY AND WESTERN TENNESSEE WILL DO. BY RAW
EXTRAPOLATION...THE LINE WOULD BE MOVING NEAR EASTERN KENTUCKY AFTER
MIDNIGHT TONIGHT. AT THIS TIME...AM GOING WITH THE MODEL CONSENSUS
THAT THE LINE WILL DIE OUT JUST AS IT ENTERS EASTERN KENTUCKY. WILL
NEED TO KEEP AN EYE ON THIS TONIGHT TO SEE WHAT IT DOES. AS THE LOWER
PORTION OF THE ATMOSPHERE DECOUPLES...IT WILL BE MUCH HARDER TO MIX
DOWN ANY STRONG WINDS TO THE SURFACE...SO IT SHOULD MAINLY BE A
THUNDERSTORM THREAT. THINGS WILL GET MORE ACTIVE AS THE UPPER TROUGH
MOVES THROUGH THE AREA TOMORROW AFTERNOON. THE SEVERE THREAT WILL
ONCE AGAIN BE AN ISSUE TOMORROW.
-- End Changed Discussion --

&&

.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...
-- Changed Discussion --
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 155 AM EDT WED MAY 22 2013

A RELATIVE LULL IN CONVECTIVE ACTIVITY SHOULD OCCUR OVER THE FIRST 6
TO 10 HOURS OF THE PERIOD. SOME ISOALTED TO SCATTERED SHRA AND
PERHAPS AN ISOALTED TSRA CANNOT BE RULED OUT OVER THE NEXT FEW HOURS
AS AN OUTFLOW BOUNDARY WORKS IN...BUT INSTABILITY IS RATHER MINIMAL
ATTM. AND/AFTER ABOUT 15Z...CONVECTION SHOULD CONTINUE TO DEVELOP AND
STRENGTHEN AND SEVERE THREAT AND STRONG WIND GUSTS COULD IMPACT ALL
THREE TAF SITES AT SOME POINT DURING THE 18Z AND 0Z PERIOD. OUTSIDE OF
ANY CONVECTION...VALLEY FOG WILL CONTINUE TO DEVELOP AND BECOME DENSE
IN RIVER VALLEYS...BEFORE DISSIPATING BY 13Z. AT THE TAF SITES...SOME
MVFR IN BR IS POSSIBLE THROUGH 12Z OR 13Z.
-- End Changed Discussion --

&&

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

$$

UPDATE...JP
SHORT TERM...JJ
LONG TERM...AR
AVIATION...JP