Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 221145 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
745 AM EDT TUE APR 22 2014

.UPDATE...
ISSUED AT 730 AM EDT TUE APR 22 2014

STILL WAITING ON THE THUNDER...IT DOES APPEAR THAT THE MAIN LINE OF
RAIN IS CROSSING EAST KENTUCKY CURRENTLY...IN LINE WITH THE LATEST
HRRR. HAVE HIGHLIGHTED THIS WITH THE HIGHEST POPS AND BEST CHANCE FOR
THUNDER FOLLOWED BY LOWER POPS INTO THE EARLY AFTERNOON. ALSO FINE
TUNED THE T AND TD GRIDS THROUGH MID MORNING BASED ON THE CURRENT OBS
AND TRENDS. THESE GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS.

&&

.SHORT TERM...(TODAY THROUGH WEDNESDAY)
ISSUED AT 340 AM EDT TUE APR 22 2014

06Z SFC ANALYSIS SHOWS A WEAK COLD FRONT APPROACHING KENTUCKY FROM A
PARENT LOW CROSSING THE EASTERN GREAT LAKES. SCATTERED LIGHT SHOWERS
ARE MOVING THROUGH EAST KENTUCKY EARLY THIS MORNING IN ADVANCE OF
THIS FRONT BENEATH HIGH AND MID LEVEL CLOUDS. SO FAR...ACTUAL
MEASUREMENT BY THE SHOWERS HAS BEEN HARD TO COME BY...BUT A FEW
PROMISING CLUSTERS ARE DEVELOPING NORTH OF INTERSTATE CORRIDOR ON
RADAR. DESPITE THE THREAT OF SHOWERS AND THE PERSISTENT CLOUD
COVER...TEMPERATURES THROUGH THE AREA HAVE BEEN ABLE TO ESTABLISH A
SMALL RIDGE TO VALLEY DIFFERENCE AS THE EASTERN VALLEYS ARE SITTING
IN THE MID 50S WHILE LOW TO MID 60S ARE FOUND ON THE RIDGES. THIS
SHOULD EVEN OUT AS THE AIR SATURATES LATER THIS NIGHT WITH A GRADUAL
UPTICK IN SHOWER COVERAGE. DEWPOINTS HAVE COME UP INTO THE LOWER 50S
FOR MOST OF THE AREA...THOUGH SOME 40S ARE FOUND ON THE RIDGES AND IN
THE FAR EAST. MEANWHILE...WINDS ARE LIGHT AND GENERALLY FROM THE
SOUTHWEST THROUGH THE AREA.

THE MODELS ARE IN GOOD AGREEMENT ALOFT AS THEY ALL DEPICT A
DEVELOPING TROUGH SWEEPING THROUGH THE NORTHEAST OHIO VALLEY LATER
TODAY PROMPTING HEIGHT FALLS ACROSS EAST KENTUCKY. THE BEST ENERGY
WITH THIS TROUGH STAYS WELL TO THE NORTH AND EAST OF KENTUCKY...WITH
SOME WEAKER AMOUNTS PASSING THROUGH THIS MORNING. THE NORTHEAST
TROUGH DOES EXIT THE REGION LATER WEDNESDAY ALLOWING HEIGHTS TO BUILD
BACK OVER KENTUCKY AMIDST RIDGING INBOUND FROM THE SOUTHERN PLAINS.
WITH THE AGREEMENT ALOFT...HAVE FAVORED A GENERAL MODEL BLEND FOR THE
SHORT TERM PORTION OF THE FORECAST. HOWEVER...FOR WEATHER DETAILS
HAVE LEANED MORE HEAVILY ON THE HIGHER RESOLUTION HRRR AND NAM12
THROUGH 00Z WEDNESDAY.

SENSIBLE WEATHER WILL FEATURE A DAMP AND COOLER DAY AS THE FRONT
GRADUALLY MAKES ITS WAY THROUGH EAST KENTUCKY. THE BEST CHANCE FOR
SOME RAIN OF NOTE WILL BE RIGHT WITH THE BOUNDARY/S PASSAGE LATER
THIS MORNING. THE THERMAL PROFILE STILL LOOKS UNSTABLE ENOUGH TO
ALLOW FOR A THUNDERSTORM THROUGH NOON ACROSS THE AREA SO WILL KEEP
THAT IN THE FORECAST. EVEN SO...THE LACK OF ANY ORGANIZATION WILL KEEP
ANY STORMS THAT OCCUR TO A MORE GARDEN VARIETY LEVEL AND ALSO PREVENT
MUCH IN THE WAY OF SOAKING RAINS FOR ALL BUT A FEW SPOTS. DRIER AND
COOLER AIR MOVES INTO THE CWA LATER THIS AFTERNOON IN THE WAKE OF THE
FRONT ENDING THE SHOWER THREAT AND EVENTUALLY CLEARING THE CLOUDS.
THE DECENT CAA BEHIND THE BOUNDARY TONIGHT WILL COMPOUND RADIATIONAL
COOLING IN THE MORE SHELTERED VALLEYS TO SEND TEMPERATURES THERE INTO
THE MIDDLE 30S. THIS...COMBINED WITH LIGHT WINDS...WILL LEAVE THEM
VULNERABLE TO PATCHY FROST BY DAWN. HAVE ADDED THIS TO THE WX GRIDS
AND WILL CONTINUE ITS MENTION IN THE HWO. FOR WEDNESDAY...AFTER A
CHILLY START...READINGS WILL CLIMB INTO THE MID 60S MOST PLACES...
THOUGH THE ARRIVAL OF MID LEVEL CLOUDS LATE IN THE DAY WILL DO LITTLE
TO HELP TEMPS RISE IN THE AFTERNOON.

STARTED OUT WITH THE BC/CONSSHORT GUIDANCE FOR THE TEMPS...
DEWPOINTS...AND WIND GRIDS FOR THE FIRST 24 HOURS OF THE FORECAST
FOLLOWED BY THE BC/CONSALL THEREAFTER. THE DEWPOINTS WERE ADJUSTED
LOWER FOR MIDDAY AND EARLY AFTERNOON ON WEDNESDAY FOR EXTRA DRY AIR
MIXDOWN. DID MAKE SOME FINE TUNE ADJUSTMENTS TO THE CONSALL FOR LOWS
TONIGHT AND HIGHS ON WEDNESDAY. AS FOR POPS...ENDED UP SIMILAR TO THE
MOS GUIDANCE TODAY AND ALSO WITH ITS LOW SINGLE DIGIT VALUES TONIGHT
AND WEDNESDAY.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 330 AM EDT TUE APR 22 2014

THE MODELS WERE IN DECENT AGREEMENT IN THE EXTENDED THIS TIME
AROUND. THE MODEL CONSENSUS IS FOR LARGE TROUGH OF LOW PRESSURE TO
MOVE EASTWARD OFF THE PACIFIC OCEAN AND ACROSS THE CONUS WEDNESDAY
NIGHT THROUGH FRIDAY NIGHT. THE MODELS DISPLAYED SOME SMALL
DIFFERENCES IN THE STRENGTH OF THIS SYSTEM AND ITS EXACT
TIMING...BUT OVERALL AGREEMENT WAS SOLID. THE SURFACE REFLECTION OF
THE UPPER TROUGH AND ITS ASSOCIATED AREA OF LOW PRESSURE WILL BE AN
AREA OF LOW PRESSURE THAT IS FAIRLY INTENSE FOR THIS TIME OF
YEAR...ALONG WITH A TRAILING COLD FRONT. BASED ON THE LATEST MODEL
DATA...IT APPEARS THAT THE FRONT ITSELF WILL NOT BE ALL THAT
IMPRESSIVE IN AND OFF ITSELF. HOWEVER...THE BOUNDARY SHOULD BE WELL
DEFINED ENOUGH...AND HAVE ENOUGH GULF MOISTURE TO TAP INTO...TO
PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS AS IT MOVES ACROSS THE
REGION THURSDAY NIGHT INTO EARLY FRIDAY MORNING. WITH A VIGOROUS
UPPER TROUGH STEERING IT...THE SURFACE SYSTEM SHOULD MOVE ACROSS THE
AREA FAIRLY QUICKLY. THAT BEING SAID...ADJUSTED THE FORECAST GRIDS
TO REFLECT ABOUT A 20 HOUR PERIOD OF PRECIPITATION BEGINNING LATE
THURSDAY AFTERNOON AND LASTING INTO LATE FRIDAY MORNING. THE LATEST
MODEL DATA SUGGESTS MODEST INSTABILITY AT BEST DURING FRONTAL
PASSAGE...SO THUNDER SHOULD BE FAIRLY ISOLATED. TEMPERATURES IN OUR
DEEPEST VALLEYS COULD DROP ENOUGH TO ALLOW FOR SOME FROST FORMATION
AROUND THE AREA. BASED ON HOW WARM IT HAS BEEN LATELY...AND HOW WARM
IT WILL BE LEADING INTO WEDNESDAY NIGHT...WILL CONTINUE WITH MENTION
OF PATCHY VALLEY FROST IN THE GRIDS FOR EARLY THURSDAY MORNING.

A SECOND WEATHER IS PROGGED TO AFFECT THE AREA OVER THE WEEKEND AND
INTO THE BEGINNING OF THE UPCOMING WORK WEEK. THE ISSUE WITH THIS
SYSTEM LIES IN THE AMOUNT OF UNCERTAINTY BETWEEN THE MODELS AS TO THE
TIMING AND INTENSITY OF THIS WEATHER SYSTEM. AS IT STANDS...THE GFS
MODEL IS PRODUCING STRONG AND MORE SLOWLY EVOLVING AREA OF LOW
PRESSURE THAN THE ECMWF. BASED ON THE LATEST RUN OF THE
ECMWF...EASTERN KENTUCKY COULD EXPERIENCE ISOLATED INSTANCES OF
PRECIPITATION BEGINNING AS EARLY AS SATURDAY AFTERNOON AND LASTING
THROUGH THE END OF THE PERIOD ON MONDAY. THE GFS...ON THE OTHER
HAND...HOLDS OFF ON INTRODUCING PRECIPITATION TO THE AREA UNTIL LATE
SATURDAY NIGHT. THE SOLUTION FOR THIS PORTION OF THE FORECAST WAS TO
GO WITH A BLEND OF THE TWO MODELS...GFS AND ECWMF...TO TRY AND
ACCOUNT FOR THE AMOUNT OF DIFFERENCE BETWEEN THEM. THAT BEING
SAID...THE FORECAST SOLUTION FOR LATE SATURDAY ONWARD IS OF LOW
CONFIDENCE...WITH A SLIGHT BIAS TOWARD THE NORMALLY MORE RELIABLE
ECMWF SOLUTION. THAT BEING SAID...WENT WITH A SLIGHT CHANCE OF
SHOWERS AND STORMS BEGINNING SATURDAY AFTERNOON IN ASSOCIATION WITH
A SLOW MOVING WARM FRONTAL BOUNDARY. THE REST OF THE WEEKEND AND
FIRST COUPLE OF DAYS OF THE WORK WEEK WILL FEATURE A MEANDERING
SURFACE FRONTAL BOUNDARY WITH SCATTERED SHOWERS AND STORMS FIRING
ALONG IT FROM TIME TO TIME. WITH INSTABILITY ONCE AGAIN
LIMITED...DECIDED TO GO WITH MENTION OF ISOLATED THUNDER ACROSS THE
AREA.

TEMPERATURES THROUGHOUT THE PERIOD...WITH THE POSSIBLE EXCEPTION OF
THURSDAY MORNINGS LOWS...SHOULD BE AT OR SLIGHTLY ABOVE NORMAL FOR
THIS TIME OF YEAR. THE WARMEST DAYS WILL LIKELY BE THURSDAY THROUGH
SATURDAY...AS THE GULF OPENS UP AS WE BECOME FIRMLY ENTRENCHED IN
THE WARM SECTOR OF A PASSING CYCLONE. HIGHS IN THE LOW TO MID 70S
WILL BE COMMON ON THESE DAYS. ONCE THE SECOND AREA OF LOW PRESSURE
BEGINS TO INFLUENCE THE REGION AND THE SURFACE FRONTS STALLS OUT
ACROSS THE AREA...TEMPERATURES WILL BE QUITE A BIT A COOLER DUE TO
THE INFLUENCE OF CLOUDS AND PRECIPITATION. HIGHS FROM SUNDAY ONWARD
WILL AVERAGE MOSTLY IN THE 60S AND SHOULD HOVER AROUND NORMAL VALUES
EACH DAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 745 AM EDT TUE APR 22 2014

VFR CONDITIONS WILL SPLIT TIME WITH SOME MVFR CIGS AND VIS OVER THE
NEXT FEW HOURS AS THE MAIN LINE OF SHOWERS MOVES THROUGH. HAVE YANKED
THE THUNDER CHANCES AS THE SHOWERS ARE NOT SHOWING MUCH SIGNS OF
BEING TOO ROBUST...SO FAR. TO COVER LINGERING SHOWERS THROUGH THE
FIRST PART OF THE AFTERNOON AND WHEN THE ACTUAL COLD FRONT GOES
THROUGH HAVE INCLUDED A VCSH MENTION IN THE TAFS. DRY AIR WILL THEN
FILTER IN LATER THIS AFTERNOON...WITH ISOLATED SHOWERS COMING TO AN
END AND CIGS RISING TO VFR AGAIN BEFORE DISSIPATING. WEST TO
NORTHWEST WINDS WILL PICK UP AT 10 TO 15 KTS FROM THE WEST THIS
MORNING...BECOMING MORE NORTH WITH TIME.

&&

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

$$

UPDATE...GREIF
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...GREIF




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