Area Forecast Discussion
Issued by NWS Jackson, KY

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000
FXUS63 KJKL 171935 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE JACKSON KY
335 PM EDT WED SEP 17 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT)
ISSUED AT 335 PM EDT WED SEP 17 2014

18Z SFC ANALYSIS SHOWS WEAK HIGH PRESSURE IN PLACE OVER EAST
KENTUCKY WITH A WAVY FRONT TO THE SOUTH OF THE STATE. ALONG THE
WESTERN EXTENT OF THIS BOUNDARY...A WAVE HAS DEVELOPED AND IS
RUNNING SOUTHEAST OVER THIS FRONT COMING OUT OF SOUTHEAST MISSOURI.
LOCALLY THE CLOUDS ARE BREAKING UP THROUGH THE SOUTHWEST PORTIONS OF
THE CWA...WHILE HOLDING ON A BIT LONGER OVER THE NORTHEAST.
TEMPERATURES VARY MAINLY ACCORDING TO THE AMOUNT OF AFTERNOON
SUNSHINE...FROM THE MID 60S NORTHEAST TO THE LOWER 70S IN THE SOUTH.
DEWPOINTS ARE GENERALLY IN THE LOW AND MID 50S THROUGH THE AREA WITH
LIGHT AND VARIABLE WINDS IN PLACE.

THE MODELS ARE IN GOOD AGREEMENT ALOFT AS THEY WEAKEN THE LARGE
NORTHEAST TROUGH THAT HAS BEEN IN PLACE FOR NEARLY A WEEK NOW. A
FEW WEAK SHORT WAVES WILL PASS THROUGH THE OHIO VALLEY DURING THIS
FILLING PROCESS. ANY MODEL DIFFERENCES THAT CROP UP WILL HAVE
RELEVANCE ONLY AFTER THE SHORT TERM PART OF THE FORECAST.
ACCORDINGLY...HAVE FOLLOWED A GENERAL MODEL BLEND AND FOCUSED ON THE
LOWER LEVEL MOISTURE OVER THE NEXT 36 TO 42 HOURS AS DEPICTED IN THE
HIGHER RESOLUTION NAM12 AND ALSO...INITIALLY...THE HRRR.

SENSIBLE WEATHER WILL FEATURE THE SFC REFLECTION...OF THE MID LEVEL
WAVE...PASSING JUST TO THE SOUTH OF THE AREA THIS EVENING WITH
MAINLY JUST AN INCREASE IN CLOUDS NOTED FOR EAST KENTUCKY. THESE
CLOUDS WILL CLEAR OUT...AS WELL...AFTER MIDNIGHT SETTING THE STAGE
FOR A NIGHT OF GOOD RADIATIONAL COOLING THAT SHOULD RESULT IN SOME
UPPER 40S IN THE NORTHERN VALLEYS BY DAWN ALONG WITH AREAS OF
FOG...LOCALLY DENSE TOWARD SUNRISE. IN THE WAKE OF THE SFC WAVE...
THURSDAY WILL SEE A RESURGENT HIGH BUILD INTO EAST KENTUCKY FROM THE
NORTH WHILE THE CLOUDS MOVE OFF TO THE SOUTH. ANY CAA WITH THIS WILL
BE COUNTERACTED BY THE AMPLE SUNSHINE TO YIELD COMFORTABLE
TEMPERATURES SIMILAR TO THOSE OF TODAY...ONCE THE FOG CLEARS.
ANOTHER GOOD NIGHT OF RADIATIONAL COOLING FOLLOWS THURSDAY NIGHT WITH
PATCHY VALLEY FOG...OR WORSE...ANTICIPATED BY DAWN WHILE TEMPS WILL
FLIRT WITH THE UPPER 40S AGAIN IN THOSE VALLEYS. BOTH TONIGHT AND
THURSDAY NIGHT...SLIGHTLY MILDER READINGS CAN BE EXPECTED ON THE
RIDGES.

THE CONSSHORT WAS USED AS A STARTING POINT FOR THE T/TD/WIND GRIDS
THROUGH THE FIRST 24 HOURS BEFORE THE SUPER BLEND WAS LOADED IN
THEREAFTER. DID AGAIN NUDGE THE LOWS TONIGHT...AND THURSDAY NIGHT...
FOR RIDGE AND VALLEY DIFFERENCES. AS FOR POPS...ENDED UP WITH SINGLE
DIGITS THROUGH THE FORECAST...IN-LINE WITH GUIDANCE.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 200 PM EDT WED SEP 17 2014

A DRY AIR MASS WILL STILL BE IN PLACE AS THE PERIOD STARTS...WITH
SPRAWLING SURFACE HIGH PRESSURE OVER NEW ENGLAND RIDGING
SOUTHWESTWARD...AND A COLD FRONT OVER THE HIGH PLAINS. GREATER LOW
LEVEL MOISTURE WILL BE LOOMING JUST SOUTHEAST OF THE APPALACHIANS.
MODELS SHOW SOME OF THIS MOISTURE MAKING ITS WAY INTO KY IN THE FLOW
AROUND THE HIGH ON FRIDAY. THE GFS AND ECMWF EVEN SHOW PRECIP AS FAR
NW AS OUR EASTERN AND SOUTHEASTERN BORDER. HOWEVER...THE GFS MOS IS
LESS THAN 20 PERCENT POP AND THE NAM IS DRY...SO WILL STAY WITH A
DRY FORECAST ON FRIDAY. A WEAKENING UPPER RIDGE WILL MOVE EAST OVER
THE REGION FRIDAY NIGHT AND SATURDAY...AHEAD OF AN AMPLIFYING TROUGH
DROPPING SOUTH FROM CANADA. THE WARMING ALOFT THAT IT BRINGS WILL
RESULT IN A STABLE ATMOSPHERE...DESPITE SURFACE DEW POINTS AND
TEMPERATURES CONTINUING TO CREEP HIGHER.

THE TROUGH WILL CONTINUE ITS AMPLIFICATION AND SOUTHEASTWARD
PROGRESS...BRINGING THE AFOREMENTIONED COLD FRONT INTO THE OHIO
VALLEY ON SUNDAY. THE FRONT SHOULD EVENTUALLY PASS THROUGH THE JKL
FORECAST AREA...BUT MODELS ARE STILL NOT LOCKED IN ON SIMILAR
TIMING. A MODEL BLEND WOULD SUGGEST SUNDAY EVENING...AND WILL
CENTER THE HIGHEST POPS AT THAT TIME...BUT WITH TEMPORAL VARIABILITY
IN MODELS...WILL USE AN EXTENDED PERIOD OF POPS WITH NOTHING ABOVE
CHANCE CATEGORY AT THIS POINT. ONCE THE SYSTEM PASSES...ANOTHER
LARGE...COOL...AND DRY SURFACE HIGH PRESSURE SYSTEM IS EXPECTED TO
PASS SLOWLY BY JUST TO OUR NORTH...BRINGING AUTUMN-LIKE WEATHER FOR OUR
LOCAL AREA.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 200 PM EDT WED SEP 17 2014

THE LAST OF THE MVFR STRATUS IS CLEARING IN THE EAST WITH A PERIOD OF
VFR CONDITIONS EXPECTED THROUGH THE REST OF THE AFTERNOON AND DURING
THE EVENING FOR ALL OF EAST KENTUCKY. THE NEXT MID LEVEL SHORTWAVE
WILL LIKELY BRING IN ADDITIONAL LOW...BUT VFR...CLOUDS TO EAST
KENTUCKY THIS EVENING. ANY CLEARING BEHIND THIS WILL ENCOURAGE FOG
FORMATION AND PATCHY DENSE DEVELOPMENT BY DAWN. HAVE BROUGHT THE
LOWEST VIS AND...BY VIRTUE...LOW CIGS TO SME AND LOZ WITH LIGHTER
FOG AND HIGHER CIGS ANTICIPATED ELSEWHERE. THE FOG AND ANY LOW CLOUDS
BURN OFF BY 14Z THURSDAY WITH VFR CONDITIONS TO FOLLOW. WINDS THROUGH
THE PERIOD WILL BE LIGHT AND VARIABLE.

&&

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

$$

SHORT TERM...GREIF
LONG TERM...HAL
AVIATION...GREIF




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