Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 210536
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1236 AM EST SUN DEC 21 2014

.UPDATE...
ISSUED AT 1028 PM EST SAT DEC 20 2014

AS EXPECTED THIS EVENING...MUCH OF THE CLOUD COVER OVER THE SOUTHERN
PORTIONS OF EASTERN KENTUCKY HAS DISSIPATED WHILE SOME LINGERING LOW
LEVEL CLOUD COVER OVER THE NORTH IS STILL HANGING AROUND. THIS WILL
ALSO ALLOW FOR VALLEY TEMPS TO DROP A BIT LOWER TONIGHT...ESPECIALLY
THE BLUEGRASS COUNTIES WHERE LINGERING CLOUD COVER FROM DURING THE
DAY HAS KEPT TEMPS DOWN INTO THIS EVENING. SO HAVE LOWERED LOW TEMPS
TONIGHT ADJUSTED CLOUD COVER. HAVE ALSO NUDGED HIGH TEMPS DOWN A
DEGREE FOR TODAY DUE TO THE COOLER START TO THE DAY AND NO
TEMPERATURE ADVECTION THROUGH THE DAY EXPECTED. A NEW ZFP HAS BEEN
ISSUED FOR THESE UPDATES.

UPDATE ISSUED AT 706 PM EST SAT DEC 20 2014

THE MAIN FORECAST CONCERN THIS EVENING APPEARS TO BE WITH CLOUD COVER
THAT IS MOVING THROUGH EASTERN KENTUCKY ASSOCIATED WITH A DISTURBANCE
THAT IS EXITING TO THE NORTHEAST AND BEHIND THIS TO THE WEST...WEAK
SURFACE HIGH PRESSURE IS NUDGING INTO THE AREA. THIS WILL ALSO INTERIM
AFFECT THE HOURLY TEMPS THROUGH THE NIGHT AND WILL ADJUST
ACCORDING. ESPECIALLY IN THE SOUTH...WHERE THIS AREA WILL LIKELY
CLEAR OUT BEFORE AREAS NORTH OF THE MOUNTAIN PARKWAY DO. SO MADE A
FEW TWEAKS TO HOURLY TEMPS AND CLOUD COVER. THE REST OF THE FORECAST
IS GOOD TO GO AND A NEW ZFP WILL NOT BE REQUIRED WITH THIS UPDATE.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 350 PM EST SAT DEC 20 2014

BROAD SURFACE HIGH PRESSURE IS CURRENTLY RESIDING ACROSS THE OHIO AND
TENNESSEE VALLEYS...WHILE WEAK AREAS OF LOW PRESSURE ARE ALIGNED
ALONG THE GULF. ALOFT...A SHORT WAVE TROUGH IS EXITING TOWARDS NEW
ENGLAND...WITH SHORT WAVE RIDGING NOSING IN ACROSS THE TENNESSEE
VALLEY. SUBSIDENCE ASSOCIATED WITH THE SHORT WAVE RIDGING IS ALLOWING
FOR SOME DECENT CLEARING ACROSS WESTERN KY/TN. THIS WILL LIKELY WORK
INTO EASTERN KENTUCKY TONIGHT...ALLOWING FOR ANOTHER NIGHT OF LOWS
BACK INTO THE 20S...WITH LOCATIONS GENERALLY WEST OF I-75 AS WELL AS
THE BLUEGRASS SEEING THE COLDER READINGS.

HIGH PRESSURE WILL MAINTAIN CONTROL INTO SUNDAY...WITH HIGHS RETURNING
TO NEAR SEASONAL VALUES IN THE MID TO UPPER 40S. MEANWHILE...THE MID
AND UPPER LEVELS WILL BE AMPLIFYING AS DEEPER TROUGHING TAKES SHAPE
ACROSS THE CENTRAL CONUS. A SOUTHERN STREAM SHORT WAVE TROUGH WILL
RIDE FROM THE ARKLATEX REGION TO ALONG THE SOUTHERN APPALACHIANS
SUNDAY NIGHT. SURFACE HIGH PRESSURE WILL LOSE ITS GRIP ACROSS THE
OHIO AND TENNESSEE VALLEYS...ALLOWING FOR MOISTURE RETURN AND SOME
INFLUENCE FROM A WEAKER SOUTHEASTERN CONUS SURFACE SYSTEM. AS
SUCH...LOWS SUNDAY NIGHT WILL BE ESTABLISHED EARLY ON...WITH SOME
UPPER 20S LIKELY IN THE NORTHEASTERN VALLEYS. TEMPERATURES WILL THEN
WARM FOR THE SECOND HALF OF THE NIGHT...AS LOW CLOUDS INCREASE
QUICKLY...AND LIGHT SOUTHEASTERLY WINDS ENGAGE. WILL MAINTAIN THE
POTENTIAL FOR A FEW SHOWERS TO THREATEN SOUTHEASTERN KENTUCKY TOWARDS
DAWN.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 350 PM EST SAT DEC 20 2014

ACTIVE PATTERN CONTINUES TO BE THE STORY AS WE MOVE INTO CHRISTMAS
WEEK. THERE IS EXPECTED TO BE A AREA OF LOW PRESSURE TRACKING NE
CENTERED OFF THE CAROLINA COAST LINE. MODELS CONTINUE TO LESSEN THE
INFLUENCE ON EASTERN KY. THEREFORE THINKING ONLY SLIGHT CHANCE TO
CHANCE POPS WILL BE POSSIBLE ACROSS THE REGION. GIVEN SE FLOW WILL
SEE A CONTINUED WARMING TREND AHEAD OF NEXT SYSTEM OF CONCERN. HIGH
TEMPERATURES MONDAY WILL GENERALLY MAKE INTO THE LOW TO MID 50S.

NOW THE SYSTEM MOST HAVE BEEN WATCHING DUE TO THE POTENTIAL
IMPLICATIONS FOR CHRISTMAS TRAVEL PLANS. HIGH AMPLITUDE TROUGH WILL
BEGIN SETTING UP ACROSS THE CENTRAL US AS WE MOVE INTO TUESDAY. POPS
WILL INCREASE FROM WEST TO EAST AS MOISTURE AND CLOUDS STREAM INTO
THE REGION. ENERGY ROUNDING THE BASE OF THIS TROUGH WILL AID IN
DEVELOPING A SURFACE LOW ACROSS THE LOWER MS RIVER VALLEY TUESDAY
AFTERNOON. THIS LOW WILL TRACK NORTH ACROSS THE TN/OH VALLEYS LATER
TUESDAY INTO TUESDAY NIGHT. THERE CONTINUES TO BE DISCONTINUITY IN
THE MODELS ON THE EXACT TRACK AND SPEED OF THIS SYSTEM. THE GFS
DEVELOPS A CUTOFF LOW AT THE 500MB LEVEL THAT TRACKS N INTO THE GREAT
LAKES ALONG WITH THE SURFACE LOW BY WEDNESDAY EVENING...HOWEVER THE
ECMWF KEEPS THE CUTOFF ACROSS THE UPPER MIDWEST BUT HAS A SIMILAR
TRACK HOWEVER IT TRACKS INTO THE GREAT LAKES EARLY WEDNESDAY. GIVEN
THIS WILL LEAN TOWARD THE BLEND FOR GUIDANCE DURING THIS PERIOD AS
MODELS CONTINUE TO RESOLVE THE TIMING AND EVOLUTION OF THE SYSTEM.

SO WHAT DOES THIS MEAN FOR SENSIBLE WEATHER...MUCH OF THE BEGINNING
STAGES OF THIS SYSTEM WILL BE ALL RAIN AS STRONG JET ENERGY CONTINUES
TO SURGE WARM AND MOIST AIR UP FROM THE S AND SW ESPECIALLY TUESDAY
NIGHT INTO EARLY WEDNESDAY. THE QUESTION REALLY BECOMES HOW QUICKLY
DO WE GET COLD AIR INTO THE REGION ON WEDNESDAY BEFORE THE MOISTURE
IS CUTOFF. THE GFS HAS SLOWED THE TIMING OF COLD AIR COMPARED TO THE
12Z ECMWF. COMPARING THE GFS TO PREVIOUS RUNS THE COLDER AIR IS
SLOWER TO MAKE IT INTO THE REGION. EITHER WAY IT DOES LOOK LIKE WE
WILL SEE A CHANGE OVER FROM RAIN TO A RAIN/SNOW MIX LATER WEDNESDAY
EVENING. TEMPERATURES WILL BE FALLING THROUGH THE DAY WITH 24 HOUR
HIGHS BEING REACH IN THE EARLY MORNING HOURS. RIGHT NOW IT WOULD
APPEAR THAT TEMPERATURES WILL NOT DROP BELOW FREEZING UNTIL WEDNESDAY
NIGHT...SO INITIALLY THINKING THIS CHANGE OVER PERIOD WILL LEAD TO
LITTLE OR NO ACCUMULATION GIVEN WARMER GROUND TEMPS. THE ISSUE
BECOMES MOVING INTO OVERNIGHT AS TEMPERATURES DROP TO AND BELOW
FREEZING. MODEL SOUNDINGS FROM THE GFS DO INDICATE ABRUPT DRYING AS
WE MOVE INTO LATER WEDNESDAY THEREFORE WOULD EXPECT MORE OF A WRAP
AROUND SNOW SHOWER SCENARIO BY THIS POINT. THIS WOULD LEAD TO LITTLE
IF ANY ACCUMULATIONS HOWEVER SLICK SPOTS COULD STILL BE A ISSUE GIVEN
THE COLDER AIR MOVING INTO THE REGION. THE CAVEAT HERE WOULD BE THE
WINDY CONDITIONS WOULD DRY THE REGION OUT AS THE COLDER AIR MOVES.
INTO THE REGION

THESE SNOW SHOWERS WILL DIE DOWN BY EARLY THURSDAY WITH HIGH PRESSURE
AND UPPER LEVEL RIDGE BUILDING INTO THE REGION. BOTH THE MODELS HAVE
COME INTO SOME ALIGNMENT IN BRINGING A FRONTAL BOUNDARY ACROSS THE
REGION FRIDAY NIGHT INTO SATURDAY. RIGHT NOW THE BLEND BRINGING
CHANCE TO SLIGHT CHANCE POPS ACROSS THE REGION.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1235 AM EST SUN DEC 21 2014

THE TAF SITES AT JKL AND SJS WILL EXPERIENCE VFR CONDITIONS THROUGH
THE END OF THE PERIOD. SYM WILL CONTINUE TO HAVE MVFR CIGS AND VSBYS
WITH FOG AND AN OVC DECK OF STRATUS CLOUDS THROUGH 7Z OR SO. BASED ON
TRENDS OBSERVED IN THE LATEST SATELLITE IMAGERY...THE CLOUDS AT SYM
SHOULD BEGIN TO SCATTER OUT NICELY BY 8Z...GIVING WAY TO CLEAR SKIES
BY 9Z. A FEW LOW AND HIGHS CLOUDS MAY MAKE THEIR WAY BACK INTO
EASTERN KENTUCKY AROUND 12Z TODAY WITH VFR CONDITIONS CONTINUING
THROUGHOUT THE DAY.

&&

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

$$

UPDATE...SHALLENBERGER
SHORT TERM...GEOGERIAN
LONG TERM...DJ
AVIATION...AR






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