Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 290601 AAC
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
201 AM EDT FRI AUG 29 2014

.UPDATE...
ISSUED AT 150 AM EDT FRI AUG 29 2014

A RIDGE OF HIGH PRESSURE CENTERED OVER THE SOUTHEASTERN CONUS
EXTENDED NORTH AND NORTHWEST INTO THE APPALACHIANS AND THE OH VALLEY
REGION. AT THE SFC HIGH PRESSURE WAS CENTERED OVER THE GREAT LAKES
REGION. MEANWHILE...A BOUNDARY IS STALLED OUT FROM SOUTHEAST VA SOUTH
INTO THE APPALACHIANS AND EAST TN AND THEN NORTHWEST TO LOW PRESSURE
OVER THE PLAINS STATES. SOME PASSING CIRRUS AND MID LEVEL CLOUDS ARE
MOVING ACROSS THE REGION AT THIS POINT AROUND THE RIDGE...ESPECIALLY
THE FAR WEST AND THE NORTH. THIS TREND IS EXPECTED TO CONTINUE
OVERNIGHT WITH THE SFC HIGH TO OUR NORTHEAST AND THE UPPER RIDGE
DOMINATING. HOURLY TEMPS...DEWPOINTS AND WINDS WERE FRESHENED UP
BASED ON THE RECENT OBSERVATION DATA.

SOME AREAS OF VALLEY FOG HAVE FORMED OR ARE EXPECTED TO FORM
OVERNIGHT...AND MIGHT BECOME DENSE IN A COUPLE OF SPOTS. HOWEVER...
IT SHOULD NOT BECOME WIDESPREAD.

UPDATE ISSUED AT 1006 PM EDT THU AUG 28 2014

UPDATED AGAIN TO BLEND LATEST OBS INTO THE FORECAST GRIDS...WITHOUT
ANY SIGNIFICANT CHANGE TO THE OVERALL FORECAST.

UPDATE ISSUED AT 711 PM EDT THU AUG 28 2014

UPDATED TO BLEND LATEST OBS INTO THE FORECAST GRIDS...WITHOUT
ANY SIGNIFICANT CHANGE TO THE OVERALL FORECAST.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY NIGHT)
ISSUED AT 331 PM EDT THU AUG 28 2014

SURFACE HIGH PRESSURE CURRENTLY REIGNS FROM THE GREAT LAKES INTO THE
OHIO VALLEY. BROAD LOW PRESSURE CENTERED ACROSS THE PLAINS HAS A WARM
FRONT BRANCHED OUT TO THE ESE...BECOMING MORE STATIONARY AND ILL-
DEFINED ACROSS SOUTHERN KENTUCKY. ALOFT...AN UPPER LEVEL RIDGE AXIS
REMAINS POISED ACROSS THE MISSISSIPPI VALLEY...WITH AN UPPER
LOW/TROUGH CRUISING INTO THE PLAINS. CONVECTION HAS POPPED UP ALONG
THE STATIONARY BOUNDARY...MAINLY ACROSS THE SOUTHWESTERN PORTION OF
THE COMMONWEALTH...WHERE BETTER INSTABILITY HAS BUILT UP DURING THE
AFTERNOON. SO FAR...ONLY A FEW SHOWERS HAVE DOTTED PORTIONS OF THE
CUMBERLAND VALLEY WITHIN EASTERN KENTUCKY.

THE MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM...WITH THE
UPPER LEVEL RIDGE AMPLIFYING AND SHIFTING EAST WITH TIME AS THE UPPER
TROUGH DAMPENS AND RIDES NORTHEAST ACROSS THE PLAINS...REACHING NEAR
THE GREAT LAKES REGION BY EARLY SATURDAY MORNING. THIS WILL KEEP
PLENTY OF HEAT AND HUMIDITY ACROSS EASTERN KENTUCKY INTO THE START OF
THE HOLIDAY WEEKEND...WITH THE THREAT OF SOME ISOLATED CONVECTION...
MAINLY DURING THE FAVORED AFTERNOON AND EARLY EVENING HOURS.

ANY ISOLATED SHOWERS AND A STRAY THUNDERSTORM WILL WIND DOWN QUICKLY
THROUGH EARLY THIS EVENING AS WE LOSE INSTABILITY. FOG WILL LIKELY
SET IN ONCE AGAIN...ALTHOUGH IT SHOULD BE MORE RESTRICTED TO THE
VALLEYS COMPARED TO LAST NIGHT. OVERNIGHT LOWS WILL GENERALLY RANGE
FROM THE LOW TO MID 60S. FOR FRIDAY...HIGH TEMPERATURES WILL APPROACH
THE 90 DEGREE MARK...WITH ISOLATED CONVECTION THREATENING DURING THE
AFTERNOON AND EVENING HOURS. FRIDAY NIGHT WILL FEATURE A MORE BALMY
NIGHT...WITH VALLEY FOG AND LOWS IN THE MID TO UPPER 60S FOR MOST.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 331 PM EDT THU AUG 28 2014

THE EXTENDED WILL BEGIN WITH A BROAD BUT WEAKENING RIDGE OF HIGH
PRESSURE PARKED OVER THE SOUTHEASTERN CONUS ON SATURDAY. AT THE SAME
TIME...THE MODELS HAVE A RATHER POTENT LOW PRESSURE SYSTEM ALOFT
APPROACHING FROM THE PLAINS. THE FRONT TRAILING FROM THIS SYSTEM
WILL PROVIDE OUR NEXT GOOD CHANCE OF RAIN SATURDAY NIGHT INTO
SUNDAY. THE PRIMARY CONCERNS WITH THIS NEXT WEATHER PATTERN WILL BE
THE LARGE AMOUNTS OF GULF MOISTURE THAT ARE LIKELY TO STREAM INTO THE
TENNESSEE AND OHIO VALLEY REGIONS...AND THE SLOWNESS OF THE FRONT TO
EXIT THE AREA. BASED ON THE CURRENT DATA...THE FRONT SHOULD STALL OUT
ACROSS THE AREA THROUGH MONDAY NIGHT. A SECOND MUCH LESS WELL DEFINED
BOUNDARY WILL THEN AFFECT THE AREA ON THE HEELS OF THE ORIGINAL
FRONT FROM THE WEEKEND. THE ISSUE WITH THE SECOND BOUNDARY IS TIMING
AND MOISTURE AVAILABILITY...WHICH THE GFS AND ECMWF WERE HANDLING
QUITE DIFFERENTLY. IN FACT...DURING THE MIDDLE OF THE WEEK...THE
ECMWF STALLS OUT ANOTHER FRONT ACROSS THE AREA...WITH AMPLE MOISTURE
INTERACTING WITH THE BOUNDARY. THE GFS...HOWEVER...KEEPS ITS BOUNDARY
MOSTLY TO OUR NORTH...ALONG WITH MOST OF THE MOISTURE ASSOCIATED WITH
IT. THAT BEING SAID...THE ECMWF SOLUTION WAS USED FOR SYSTEM
EVOLUTION AND PRECIPITATION COVERAGE AND AMOUNTS FROM SATURDAY
THROUGH MONDAY NIGHT. AFTER THAT...A BLEND OF THE TWO MODELS WAS USED
TO CREATE THE NEW FORECAST...WITH LOWER THAN MEXMOS VALUES FOR POPS
EACH OF THOSE DAYS AND NIGHTS DO TO THE UNCERTAINTY. THE BEST TIME
FRAME FOR RAIN LOOKS TO BE SATURDAY NIGHT THROUGH MONDAY NIGHT DUE TO
THE STALLED FRONT. THERE WILL ALSO BE THE POTENTIAL FOR LOCALLY HEAVY
RAINFALL TO START THE PERIOD AS THE LATEST FORECAST SOUNDINGS ARE
PREDICTING BETWEEN 1.8 TO JUST OVER 2 INCHES OF PRECIPITABLE WATER
AND A TALL SKINNY CAPE PROFILE. THIS WILL BEAR WATCHING OVER THE NEXT
COUPLE OF DAYS. BASED ON THIS TYPE OF INSTABILITY PROFILE...THE
POTENTIAL FOR THUNDERSTORM ACTIVITY SHOULD BE A LITTLE LESS THAN WE
HAVE SEEN OVER THE PAST WEEK OR SO.

TEMPERATURES THROUGHOUT MOST OF THE PERIOD LOOK TO BE SLIGHTLY
WARMER THAN NORMAL DUE TO PERSISTENT SOUTHERLY FLOW ASSOCIATED WITH
EACH OF THE PASSING WEATHER SYSTEMS AND THE LARGE AMOUNT OF WARM
MOIST AIR THAT WILL BE TRANSPORTED INTO THE AREA OFF THE GULF OF
MEXICO. HIGHS EACH DAY WILL AVERAGE IN THE MID TO UPPER 80S...WITH
OVERNIGHT LOWS BOTTOMING OUT AROUND 70. THE ONE EXCEPTION TO THIS
RULE WOULD BE SUNDAY...WHICH SHOULD SEE COOLER THAN NORMAL
TEMPERATURES DUE TO THE EXTENSIVE CLOUD AND LONG LASTING
PRECIPITATION THAT IS EXPECTED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 158 AM EDT FRI AUG 29 2014

IFR OR WORSE FOG IS EXPECTED TO DEVELOP LATE TONIGHT NEAR VALLEYS OF
LARGE STREAMS. THE FOG WILL DISSIPATE BY AROUND 13Z FRIDAY...LEAVING
PREVAILING VFR. AT THE TAF SITES...MAINLY MVFR FOG IS EXPECTED FOR A
FEW HOURS BETWEEN ABOUT 8Z AND 13Z. THIS MIGHT DROP INTO THE IFR
RANGE AT SJS FOR A COUPLE OF HOURS AROUND 11Z. OTHERWISE...ONCE THE
FOG DISSIPATES... ISOLATED THUNDERSTORMS ARE EXPECTED AFTER 16Z...AS
A BOUNDARY CURRENTLY STALLED OUT TO OUR SOUTH RETURNS NORTH AS WARM
FRONT. VIS AND OR CIGS COULD DROP BRIEFLY TO IFR OR LOWER IN ANY
LOCATION THAT IS DIRECTLY AFFECTED BY ANY TSRA.

&&

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

$$

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






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