Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 202053 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 353 PM EST SAT DEC 20 2014 .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 INFLUECE 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 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 134 PM EST SAT DEC 20 2014 EXPECT MAINLY VFR CONDITIONS TO REIGN ACROSS MOST LOCATIONS THROUGH THE PERIOD. THE ONLY EXCEPTION WILL BE NEAR THE I-64 CORRIDOR...WHERE SOME MVFR CEILINGS WILL LINGER EARLY THIS AFTERNOON...BEFORE LIFTING. CLOUD DECKS WILL RANGE FROM 5-7K FEET AGL THROUGH THIS EVENING...BEFORE SCATTERING OUT FROM SOUTHWEST TO NORTHEAST THROUGH THE NIGHT. WINDS WILL REMAIN LESS THAN 5 KTS THROUGH THE PERIOD AS WELL. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GEOGERIAN LONG TERM...DJ AVIATION...GEOGERIAN

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