Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 170926 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 426 AM EST WED DEC 17 2014 .SHORT TERM...
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(TODAY THROUGH THURSDAY) ISSUED AT 426 AM EST WED DEC 17 2014 A WEAK BOUNDARY PASSING THROUGH THE REGION OVERNIGHT HAS PROMPTED A SLIGHT INCREASE IN MOISTURE...WHICH HAS RESULTED IN LIGHT RAIN SHOWERS ACROSS A GOOD PORTION OF THE NORTHERN HALF OF THE CWA. AS THE BOUNDARY /WHICH IS IN THE FORM OF A WEAK COLD FRONT CONNECTED TO LOW PRESSURE CURRENTLY TRACKING ACROSS THE LOWER GREAT LAKES/ CONTINUES EASTWARD OUT OF KY...EXPECT SHOWERS TO COME TO AN END FROM W TO E THROUGH 11Z. FORECAST SOUNDINGS ARE STILL SUPPORTING DRIZZLE HANGING AROUND MUCH OF THE AREA THROUGH MID MORNING TO EARLY AFTERNOON AS A STRONG SUBSIDENCE INVERSION KEEPS LOW LEVEL MOISTURE IN PLACE. BETWEEN 15 AND 18Z...DRY AIR WILL FINALLY BEGIN TO MIX DOWN...AND LOW CLOUDS WILL BREAK. UNFORTUNATELY...HIGH CLOUDS WILL BE BUILDING IN AROUND THE SAME TIME AS THE NEXT SYSTEM APPROACHES THE REGION. WENT ABOVE GUIDANCE ON CLOUD COVER...KEEPING BKN CLOUDS ACROSS MUCH OF THE CWA AS THIS TRANSITION OCCURS. CONCERNING THE APPROACHING SYSTEM...A SHORTWAVE IS EXPECTED TO DEVELOP ALONG THE LEEWARD SIDE OF AN UPPER LEVEL TROUGH WHICH WILL BE SITTING ALONG THE PACIFIC COAST TODAY. AS THIS SHORTWAVE RACES OUT AHEAD OF THE TROUGH...IT WILL CREATE A DISTURBANCE WHICH WILL BEGIN PULLING MOISTURE IN FROM THE GULF COAST AS IT REACHES THE MISSISSIPPI RIVER VALLEY WEDNESDAY NIGHT/THURSDAY MORNING. ALL MODELS ARE SHOWING PRECIP REACHING WESTERN AND SOUTH CENTRAL KY BETWEEN 6 AND 12Z THURSDAY. HOWEVER...DIGGING A LITTLE DEEPER...THIS SYSTEM IS NOT ALL THAT IS APPEARS. FIRST OFF...KY WILL BE UNDER THE INFLUENCE OF A STRONG HIGH PRESSURE SYSTEM AT THE SURFACE. FURTHER MORE...FORECAST SOUNDINGS ARE SHOWING A STRONG LAYER OF DRY AIR NEAR THE SURFACE IN RESPONSE TO THE SURFACE HIGH. WHAT MOISTURE ACCOMPANIES THIS SHORTWAVE WILL BE SHALLOW...AND WILL HAVE TO FALL THROUGH A FAIRLY SUBSTANTIAL AMOUNT OF LOW LEVEL DRY AIR. AFTER COLLABORATION WITH SURROUNDING OFFICES...DECIDED TO SUBSTANTIALLY DROP POPS FROM GUIDANCE. SINCE MODELS WERE PLACING THE BEST POTENTIAL FOR PRECIP ACROSS OUR SW COUNTIES IN THE CWA...DID KEEP SLIGHT CHANCES HERE. HOWEVER FOR EVERYWHERE ELSE...WILL MORE THAN LIKELY SEE A SPRINKLE/FLURRY EVENT BASED ON THE GFS AND NAM SOUNDINGS. THE SHORTWAVE WILL QUICKLY PHASE OUT ACROSS KY...WITH ANY LINGERING PRECIP EXPECTED TO END THURSDAY EVENING...THOUGH SOME MID LEVEL CLOUDS WILL LIKELY STICK AROUND. FAIRLY ZONAL FLOW AND ABUNDANT CLOUD COVER ACROSS THE REGION WILL WORK TO KEEP FAIRLY STEADY TEMPS IN THE FORECAST FOR THE NEXT 36 TO 48 HOURS. HIGHS WILL BE IN THE UPPER 30S AND LOW 40S...WITH A FAIRLY SMALL DIURNAL DROP TO THE UPPER 20S TO AROUND 30 DURING THE OVERNIGHT. .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 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT) ISSUED AT 127 AM EST WED DEC 17 2014 WHILE AREAS OF DRIZZLE ARE ONGOING ACROSS MUCH OF EASTERN KY...THE NORTHEAST PORTION OF THE STATE /GENERALLY AREAS NORTH OF THE MOUNTAIN PARKWAY/... HAVE ACTUALLY SEEN A INCREASE FROM DRIZZLE TO LIGHT RAIN SHOWERS. EXPECT THIS RAIN TO HAVE LITTLE DIFFERENCE IN IMPACTS TO THAT OF THE DRIZZLE...SO WILL JUST CONTINUE WITH DRIZZLE MENTION AT THIS TIME IN TAFS...ESPECIALLY GIVEN THAT THE RAIN SHOWERS SHOULD TAPER OFF AT KSYM...KJKL...AND KSJS OVER THE NEXT COUPLE HOURS. MEANWHILE...CIGS SHOULD REMAIN BETWEEN IFR AND MVFR THROUGH THE REMAINDER OF THE NIGHT...THEN MVFR THROUGH A MAJORITY OF THE DAY TOMORROW...AT LEAST UNTIL DRY AIR IS FINALLY ABLE TO MIX DOWN TO THE SURFACE...CUTTING OFF DRIZZLE POTENTIAL...AND SLOWLY BREAKING THE LOW CLOUD DECK. LATEST GFS FORECAST SOUNDINGS ARE SHOWING THIS OCCURRING SOMETIME BETWEEN 18 AND 21Z...WHILE THE NAM TRIES TO HOLD ON TO THE MOISTURE A BIT LONGER. LEANED MORE TOWARDS THE GFS SOLUTION AT THIS TIME. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JMW LONG TERM...KAS AVIATION...JMW

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