Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 241207
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
807 AM EDT FRI APR 24 2015

.UPDATE...
ISSUED AT 807 AM EDT FRI APR 24 2015

UPDATED TO BLEND EARLY MORNING OBS INTO THE FORECAST. NO
SUBSTANTIAL CHANGES WERE MADE.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 416 AM EDT FRI APR 24 2015

COOL SURFACE HIGH PRESSURE WAS OVERHEAD EARLY THIS MORNING...WITH
SUBFREEZING TEMPERATURES IN MANY PLACES. AN UPPER LEVEL RIDGE WAS
JUST TO OUR WEST...AND HIGH CLOUDS WERE SPILLING OVER THE RIDGE
INTO OUR SOUTHWEST COUNTIES. THE NEXT STORM SYSTEM WAS TAKING
SHAPE OVER THE PLAINS...AND WILL HEAD EAST TO THE LOWER OHIO
VALLEY BY THE END OF THE PERIOD. THE SURFACE HIGH WILL MOVE TO OUR
EAST TODAY AND WARM AIR ADVECTION WILL BRING GULF OF MEXICO
MOISTURE NORTHWARD AHEAD OF THE NEXT STORM SYSTEM. THIS WILL CAUSE
CLOUDS TO LOWER AND THICKEN THIS AFTERNOON AND EVENING...AND
SHOWERS WILL DEVELOP FROM SW TO NE LATE TONIGHT AND ON SATURDAY
MORNING. BOTH THE GFS AND NAM SUGGEST THE PRECIP ASSOCIATED WITH
THE WARM AIR ADVECTION WILL SHIFT TO OUR NE ON SATURDAY
AFTERNOON...AND A WARM FRONT WILL MOVE NORTH INTO KY. AREAS NEAR
AND SOUTH OF THE WARM FRONT ARE EXPECTED TO BECOME VERY UNSTABLE.
THE GREATEST INSTABILITY IN THE JKL FORECAST AREA SHOULD BE OVER
THE CUMBERLAND RIVER BASIN. FORECAST SOUNDINGS SHOW STRONG
SHEAR...DRY MID LEVELS...AND LARGE MID LEVEL CAPE IN THAT AREA. IF
THUNDERSTORMS ARE ABLE TO DEVELOP NEAR THE WARM FRONT AND IN THE
WARM SECTOR AS SURFACE LOW PRESSURE APPROACHES FROM THE WEST AT
THE END OF THE DAY...THEY WOULD POSE A SIGNIFICANT SEVERE WX
THREAT. LARGE HAIL IS ESPECIALLY A CONCERN...BUT DAMAGING WINDS
AND TORNADOES COULD ALSO OCCUR.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 330 AM EDT FRI APR 24 2015

THE MODELS HAVE FINALLY COME INTO PRETTY AGREEMENT IN THE
EXTENDED. THE LATEST RUN OF THE GFS NOW CLOSELY RESEMBLES THE
LATEST ECMWF FOR MOST OF THE EXTENDED PERIOD. THE PERIOD IS
PROGGED TO START OFF WITH FAIRLY WIDESPREAD RAINFALL ACROSS
EASTERN KENTUCKY. BASED ON THE LATEST MODEL SOUNDINGS...IT ALSO
APPEARS THERE WILL BE A GOOD CHANCE OF SOME THUNDERSTORMS ONGOING
AT THE START OF THE PERIOD...LIKELY THROUGH EARLY SUNDAY MORNING
BEFORE THE INSTABILITY AND LIFT MOVES FAR ENOUGH EAST FOR THUNDER
TO COME TO AN END. LOCALLY HEAVY RAINFALL WILL POSSIBLE DURING THE
HIGHEST PRECIPITATION PROBABILITIES. AFTER THE LAST OF THE RAIN
FINALLY EXITS THE AREA SUNDAY AFTERNOON...THE RESIDENTS OF EASTERN
KENTUCKY SHOULD EXPERIENCE A NICE BREAK FROM THE WET WEATHER TO
BEGIN THE NEW WORK WEEK. THE MODELS BOTH AGREE THAT A RIDGE OF
HIGH PRESSURE...BOTH AT THE SURFACE AND ALOFT...IS EXPECTED TO
MOVE SLOWLY ACROSS THE OHIO AND TENNESSEE VALLEY REGIONS MONDAY
AND TUESDAY. THIS RIDGE WILL BRING DRY AND WARMING WEATHER TO THE
AREA TO START THE WEEK.

A RATHER WELL DEVELOPED AREA OF LOW PRESSURE IS THEN FORECAST TO
MIGRATE ACROSS CENTRAL MISSISSIPPI...ALABAMA...AND GEORGIA
WEDNESDAY THROUGH THURSDAY. THE MODELS DO DIFFER A BIT
HERE...HOWEVER...IN THAT THE ECMWF BRINGS MORE MOISTURE NORTHWARD
INTO THE OHIO VALLEY THAN THE GFS DOES. THE ECMWF SOLUTION ALSO
BRINGS HAS ITS AREA OF LOW PRESSURE MOVING ALONG TRACK THAT IS
FURTHER NORTH THAN THE GFS. THE END RESULT IS FOR THE ECMWF
SOUTHERN TRACK LOW TO PHASE WITH A TROUGH OF LOW PRESSURE THAT IT
HAS MOVING DOWN FROM THE GREAT LAKES AREA WEDNESDAY NIGHT AND
THURSDAY...WHILE THE GFS KEEPS ITS SOUTHERN TRACK LOW FAR ENOUGH
SOUTH THAT IT DOES NOT COUPLE WITH THE NORTHERN STREAM TROUGH.
THEREFORE...THE ECMWF IS PRODUCING QUITE A BIT MORE PRECIPITATION
ACROSS EASTERN KENTUCKY TOWARD THE END OF THE PERIOD THAN THE GFS.
WITH UNCERTAINTY STILL EXISTING DURING THIS PART OF THE
EXTENDED...DECIDED TO KEEP IN PRECIPITATION FOR THE WEDNESDAY
THURSDAY TIME PERIOD...BUT WITH MUCH LOWER PROBABILITIES THAN THE
LATEST ECMWF MODEL DATA ARE CURRENTLY SUGGESTING.

DAYTIME HIGHS IN THE EXTENDED LOOK TO BE BELOW NORMAL DURING THE
PERIODS WITH WIDESPREAD CLOUD COVER AND PRECIPITATION...AND CLOSE
TO NORMAL TOWARD THE END OF THE PERIOD WHEN THE WEATHER IS
EXPECTED TO BE DRY. OVERNIGHT LOWS ARE EXPECTED TO FOLLOW THE SAME
GENERAL PATTERN...WITH NORMAL VALUES ON TAP FOR THE END THE
PERIOD.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 807 AM EDT FRI APR 24 2015

VFR CONDITIONS ARE EXPECTED THROUGH LATE TONIGHT. RAIN WILL MOVE
IN FROM THE SOUTHWEST OVERNIGHT AND CEILINGS WILL LOWER TO MVFR
TOWARD DAWN. LIGHT WINDS ARE EXPECTED THROUGH THE PERIOD.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

UPDATE...HAL
SHORT TERM...HAL
LONG TERM...AR
AVIATION...HAL


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