Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 162015 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 315 PM EST TUE DEC 16 2014 .SHORT TERM...
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(THIS EVENING THROUGH WEDNESDAY NIGHT) ISSUED AT 315 PM EST TUE DEC 16 2014 19Z SFC ANALYSIS SHOWS A FAIRLY DEEP AREA OF LOW PRESSURE LIFTING NORTHEAST THROUGH THE EASTERN GREAT LAKES. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM IS NOW THROUGH EASTERN KENTUCKY AND AS A RESULT GUSTY WEST WINDS ARE BRINGING IN A COLDER AIR MASS. AS IT DOES SO... IT IS ALSO GENERATING A SUBSTANTIAL AREA OF DRIZZLE AND LOWER CIGS. TEMPERATURES VARY FROM THE LOW 40S WEST TO NEAR 50S EAST ACROSS THE CWA WITH DEWPOINTS IN THE UPPER 30S TO LOWER 40S. THE MODELS ARE IN DECENT ENOUGH AGREEMENT ALOFT THROUGH THE SHORT TERM PORTION OF THE FORECAST AS THEY ALL DAMPEN OUT THE CURRENT TROUGH OVER THE AREA WHILE ABSORBING IT INTO THE MAIN MID LEVEL LOW OVER THE UPPER MIDWEST. THIS WILL KEEP FAST...WEST TO EAST...FLOW ABOVE EASTERN KENTUCKY INTO THE DAY WEDNESDAY...THOUGH MODEL DIFFERENCES START TO MAGNIFY BY DAWN. THE ECMWF IS SLOWER MOVING THIS MIDWEST LOW EAST COMPARED TO THE GEM AND GFS WHICH WILL ALSO SERVE TO KEEP OUR HEIGHTS SLIGHTLY SUPPRESSED INTO WEDNESDAY EVENING. DESPITE THIS...THE PREFERRED ECMWF DOES NOT LAG IN BRINGING THE NEXT BATCH OF ENERGY INTO THE REGION FROM A QUICK MOVING WAVE PASSING OUT OF THE SOUTHERN PLAINS. THIS WILL SEEP INTO OUR SOUTHWEST PARTS BY THURSDAY MORNING. FOR THE FORECAST...FOLLOWED A BLEND OF THE HIGHER RESOLUTION HRRR AND NAM12 WITH SOME ADJUSTMENT TOWARD THE MAIN FEATURES IN THE LATEST ECMWF. A DREARY EVENING AND OVERNIGHT IS ANTICIPATED THROUGH EASTERN KENTUCKY AS LOW CIGS AND DRIZZLE WILL DOMINATE UNDER A SUBSIDENCE INVERSION...PARTICULARLY OVER THE NORTHERN HALF THE CWA. THERE IS A CONCERN THAT THE HIGHER POINTS OF EASTERN KENTUCKY FALL TO FREEZING...OR A COUPLE OF DEGREES BELOW...BY DAWN GIVEN THE CAA OVERNIGHT. COMBINED WITH THE AREAS OF DRIZZLE STILL AROUND...THERE WILL BE A THREAT OF FREEZING DRIZZLE GENERALLY ABOVE 2000 FEET. FOR THIS...WILL ISSUE AN SPS FROM LATE TONIGHT INTO THURSDAY MORNING FOR OUR SOUTHEASTERN-MOST COUNTIES WITH THAT HIGHER TERRAIN. THE LOW CLOUDS WILL PROBABLY HOLD TOUGH INTO THE FIRST PART OF THE DAY WEDNESDAY BUT THERE COULD BE SOME BREAKUP MAKING FOR A BRIEF PERIOD OF SUNSHINE DURING THE AFTERNOON AHEAD OF THE NEXT BATCH OF HIGHER CLOUDS DUE IN HERE LATER THAT EVENING. THESE NEXT CLOUDS WILL QUICKLY INCREASE AND LOWER THROUGH THE NIGHT WITH EVEN SOME LIGHT RAIN OR SNOW POSSIBLE BY DAWN THURSDAY...THOUGH TEMPERATURES WILL BE MILDER THAN TONIGHT IN MOST PLACES. USED THE BCCONSSHORT AS A STARTING POINT FOR THE T/TD/WIND GRIDS FOR THE FIRST 20 HOURS BEFORE POPULATING WITH THE SUPERBLEND THEREAFTER. THESE WERE THEN SUBJECTED TO MINOR ADJUSTMENTS FOR TERRAIN EFFECTS MAINLY TONIGHT AND WEDNESDAY NIGHT. AS FOR POPS...ENDED UP JUST ABOVE THE HIGHER MET MOS GUIDANCE TONIGHT GIVEN THE LOW QPF BUT MODERATE POPS WITH EXTRA EMPHASIS ON DRIZZLE AS PTYPE. ALSO...FOR LATE WEDNESDAY WENT A BIT HIGHER THEN GUIDANCE IN THE SOUTHWEST GIVEN THE FAST FLOW REGIME. .LONG TERM...(THURSDAY THROUGH TUESDAY) ISSUED AT 245 PM EST TUE DEC 16 2014 PROGRESSIVE PATTERN WILL CONTINUE THROUGH THE EXTENDED. THE PERIOD WILL START AS A MID LEVEL TROUGH CROSSES INTO THE OHIO RIVER VALLEY ON THURSDAY. MODELS HAVE TRENDED MORE AGGRESSIVE WITH THIS FEATURE WITH THE 12Z SUITE OF MODELS WITH GFS EVEN SHOWING SOME MODEST LIFT ABOVE 850MB. THE MAIN LIMITING FACTOR FOR PRECIPITATION ON THURSDAY WILL BE THE LOW LEVEL DRY AIR. HOWEVER...GIVEN THE DEEP MOISTURE STARTING AROUND 5KFT...THIS SHOULD BE ENOUGH TO AT LEAST WARRANT A CHANCE OF MEASURABLE PRECIPITATION REACHING THE GROUND. HOWEVER...THIS PRECIPITATION MAY DRY UP AS IT TRIES TO PUSH NORTHWARD THROUGH THE DAY. THUS...PLAN TO GO WITH CHANCE POPS ACROSS THE SOUTH...TRAILING OFF TO SLIGHT CHANCE IN THE NORTH. ALL OF THIS PRECIPITATION AS EXPECTED WILL REMAIN LIGHT...BUT SOME SNOWFLAKES COULD MIX IN AT TIMES THROUGH THE DAY. HIGH PRESSURE WILL PROVIDE DRY WEATHER THURSDAY NIGHT THROUGH FRIDAY. THE WEATHER TURNS MORE INTERESTING BY FRIDAY NIGHT THROUGH SATURDAY AS A SOUTHERN STREAM SHORTWAVE PUSHES EAST ACROSS THE SOUTHERN TIER OF THE US. THIS SYSTEM IS NOT EXPECTED TO GET MUCH HELP FROM THE NORTHERN STREAM...AND THUS...NOT MUCH COLD AIR IS EXPECTED TO GET WORKED INTO THIS SYSTEM. THIS FACT...COMBINED WITH A WEAKENING AREA OF LOW PRESSURE TRACKING ACROSS THE GULF COAST STATES WILL LIKELY YIELD VERY LITTLE SNOW POTENTIAL. HOWEVER...WE ARE ON THE NORTH SIDE OF THIS SYSTEM...WHICH WOULD BE THE BEST SPOT FOR ANY SNOW. PRECIPITATION IS EXPECTED TO SPREAD INTO THE AREA LATE FRIDAY NIGHT AND CONTINUE THROUGH SATURDAY. BEST SNOW POTENTIAL MAY BE AT THE ONSET FRIDAY NIGHT...BUT AGAIN...PRECIPITATION RATES MAY BE FAIRLY LIMITED...KEEPING SNOW AMOUNTS FROM BEING ALL THAT HIGH. IN FACT...WE COULD SEE A MIX OF RAIN/SNOW RIGHT THROUGH SATURDAY WITH VERY LITTLE SNOW ACCUMULATION FOR MUCH OF THE AREA. THE ECMWF REMAINS THE COLDER OF THE MODELS SUGGESTING BETTER SNOW POTENTIAL...WHILE THE GFS HAS MAINTAINED ITS ALL RAIN FORECAST. GOING WITH A COMPROMISE ON HIGHS ON SATURDAY WOULD BE TEMPERATURES AROUND 40 BY THE AFTERNOON ACROSS MUCH OF THE AREA. ITS POSSIBLE SOME COOLER READINGS IN THE 30S COULD KEEP MORE SNOW GOING A BIT LONGER ACROSS THE NORTHERN PORTION OF THE AREA...BUT WITH WEAK PRECIP RATES...COMBINED WITH ABOVE FREEZING TEMPERATURES...SHOULD REALLY CUT INTO ANY SNOWFALL POTENTIAL EVEN WITH THE COLDER ECMWF SOLUTION. PRECIPITATION WILL WIND DOWN BY SATURDAY NIGHT GOING OVER TO A PERIOD OF LIKELY DRIZZLE. DRY WEATHER WILL RETURN FOR SUNDAY AND PERSIST INTO THE EARLY PART OF NEXT WEEK. TEMPERATURES ARE EXPECTED TO REMAIN FAIRLY SEASONABLE THROUGH THE END OF THE FORECAST PERIOD.
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&& .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON) ISSUED AT 145 PM EST TUE DEC 16 2014 THE COLD FRONT HAS PASSED THROUGH EASTERN KENTUCKY TAKING THE LIGHT RAINS ALONG WITH IT. HOWEVER...A LARGE AREA OF DRIZZLE DOES FOLLOW THIS BOUNDARY AND WILL AFFECT MUCH OF THE FA INTO THE EVENING. IN FACT...FORECAST SOUNDINGS AND TIME HEIGHTS CONTINUE TO INDICATE A STRONG SUBSIDENCE INVERSION BEHIND THE FRONT...WITH LOW LEVEL MOISTURE TRAPPED THROUGH MOST OF THE TAF PERIOD. THIS WILL LEAD TO LOWERING CIGS AND THE POTENTIAL FOR DRIZZLE THROUGH WEDNESDAY MORNING. FUEL ALTERNATES ARE LIKELY AS WE HEAD INTO THE OVERNIGHT HOURS. ANOTHER CONCERN WILL BE THE WINDS. EXPECT WINDS AT THE SURFACE TO STAY UP FROM THE WEST WITH GUSTS BETWEEN 15 AND 20 KTS THROUGH THE REST OF THE AFTERNOON. THE OVERNIGHT SUBSIDENCE INVERSION SHOULD ALLOW SFC WINDS TO DIE DOWN AND BECOME LIGHT FOLLOWING SUNSET. THE WINDS WILL PICK UP FROM THE WEST TO NORTHWEST DURING THE DAY WEDNESDAY AT 5 TO 10 KTS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...KAS AVIATION...GREIF

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