Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 181525 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1025 AM EST THU DEC 18 2014 .UPDATE...
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ISSUED AT 1025 AM EST THU DEC 18 2014 14Z SFC ANALYSIS SHOWS A VERY WEAK AREA OF LOW PRESSURE SLIDING BY TO THE SOUTH OF EASTERN KENTUCKY. THE PRECIPITATION WITH THIS...MAINLY FLURRIES...IS FADING FAST WITH MOSTLY VIRGA LEFT. TEMPERATURES ARE GENERALLY IN IN THE UPPER 20S AND LOWER 30S THROUGH THE AREA WITH DEWPOINTS IN THE MID AND UPPER 20S...WHILE WINDS ARE LIGHT. SATELLITE SHOWS A FEW BREAKS OUT THERE BUT CIGS ARE MAINLY IN THE LOW MVFR RANGE NORTH AND VFR SOUTH. HAVE UPDATED THE FORECAST TO DIMINISH THE POPS QUICKLY THROUGH MIDDAY IN CONJUNCTION WITH THE 12Z NAM12 AND LATEST HRRR. ALSO FINE TUNED HIGH TEMPERATURES AND THE HOURLY T/TD GRIDS PER THE LATEST OBS...TRENDS...AND CONSSHORT GUIDANCE. THESE HAVE BEEN SENT TO THE NDFD AND WEB SERVERS ALONG WITH AN UPDATE TO THE HWO AND ZONES. UPDATE ISSUED AT 552 AM EST THU DEC 18 2014 THERE IS A FAIR AMOUNT OF RADAR RETURNS MAKING IT INTO SOUTHEAST KY...UNLIKE WHAT MANY OF THE HI RES MODELS WERE SHOWING EARLIER. DESPITE THE DRY AIR IN PLACE AT THE SURFACE...DEW POINT DEPRESSIONS HAVE LESSENED TO 0 IN SOME OF OUR SOUTHWESTERN COUNTIES. AND WITH SNOW AND SLEET BEING REPORTED ONLY A FEW COUNTIES OVER...DECIDED IT WAS TIME TO GO AHEAD AND EXPAND THE CHANCES FOR PRECIP THIS MORNING. AS IT IS NOW...IT LOOKS LIKE ALL OF THE COUNTIES ALONG THE TENNESSEE BORDER...AS WELL AS THE NEXT TIER OF COUNTIES NORTHWARD WILL LIKELY BE AFFECTED BY LIGHT SNOW AND POTENTIAL SLEET THIS MORNING. LATEST HI RES MODELS...INCLUDING THE HRRR AND NAM 12 ARE SHOWING THE SYSTEM LOSING INTENSITY VERY QUICKLY THIS MORNING...AND CUTTING OFF PRECIP CHANCES ACROSS OUR CWA WITHIN THE NEXT FEW HOURS. HOWEVER...GIVEN THE LEVEL OF UNCERTAINTY...AND THE ONGOING STRONG REFLECTIVITIES...ERRED ON THE PESSIMISTIC SIDE AND KEPT MENTION OF SNOW AND ICE IN UNTIL MID MORNING. ALSO...WENT AHEAD AND ISSUED A SPECIAL WEATHER STATEMENT THROUGH 15Z FOR THE AFFECTED COUNTIES SINCE ANY PRECIP WILL LIKELY ACCUMULATE ON SURFACES DURING THE MORNING COMMUTE.
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&& .SHORT TERM...(TODAY THROUGH FRIDAY) ISSUED AT 358 AM EST THU DEC 18 2014 SURFACE HIGH PRESSURE CONTINUES TO BE IN CHARGE FOR THE OHIO RIVER VALLEY AND MANY POINTS TO OUR NORTH AND SOUTH. STRONG SUBSIDENCE TRAPPING LOW LEVEL MOISTURE ACROSS THE NE PORTION OF THE CWA HAS LED TO CONTINUED MVFR CLOUDS...WHICH ACCORDING TO THE LATEST FORECAST SOUNDINGS...SHOULDN/T BE BUDGING UNTIL SOMETIME EARLY THIS AFTERNOON. MEANWHILE...ALOFT...A SHORTWAVE IS CONTINUING TO DAMPEN AS IT TRACKS EASTWARD...AND SHOULD BE POISED TO REACH THE MISSISSIPPI RIVER VALLEY BETWEEN 12 AND 18Z TODAY. SO FAR...THIS SYSTEM HAS BROUGHT LIGHT PRECIP ACROSS FAR SW KY...AS IT CONTINUES TO SHIFT EASTWARD TOWARDS OUR SW CWA DURING THE EARLY MORNING HOURS. THE AMOUNT OF LOW LEVEL DRY AIR IS STILL A CONCERN IN THIS AREA OF THE CWA...AND WHETHER OR NOT THE PRECIP CAN OVERCOME IT. EXPECTING BEST CHANCES FOR WEATHER ACROSS WAYNE AND MCCREARY COUNTIES GIVEN THE LATEST HI RES MODEL DATA...INCLUDING THE HRRR AND ECMWF. FORECAST SOUNDINGS ARE SHOWING BELOW FREEZING SURFACE TEMPS AT THESE LOCATIONS...BUT WITH THE POTENTIAL FOR A SLIGHT WARM NOSE TEETERING ALONG THE FREEZING LINE SEVERAL THOUSAND FEET ABOVE GROUND THROUGH 18Z. AS SUCH...WENT AHEAD AND MENTIONED SOME ICE PELLETS ALONG WITH A CHANCE OF SNOW IN THESE TWO COUNTIES...WITH A SLIGHT CHANCE OF LIGHT SNOW EVENTUALLY MIXING WITH RAIN AFTERWARDS ELSEWHERE IN THE SW CWA. THE SHORTWAVE WILL EVENTUALLY FLATTEN AND SHIFT EAST OF KY BY 06Z FRIDAY ELIMINATING ANY FURTHER PRECIP CONCERNS FOR THE SHORT TERM. THE ONE CAVEAT WILL BE THE EXISTENCE OF THE MID LEVEL CLOUDS WITH MUCH OF THE TEMPERATURE PROFILE /INCLUDING SURFACE TEMPS/ DROPPING BELOW FREEZING BY THIS EVENING AND THROUGHOUT THE OVERNIGHT. A FEW FLURRIES MAY GET SQUEEZED OUT ACROSS THE CWA DURING THE EVENING. IN FACT...MAY NOT HAVE EXTENDED THE FLURRY POTENTIAL FAR ENOUGH ACROSS THE CWA. BUT THE CONFIDENCE IS STILL QUITE LOW ON THIS SUBJECT. CONTINUED TO GO ABOVE GUIDANCE FOR CLOUD COVER OVER THE NEXT 36 HOURS AS MID/LOW LEVEL CLOUDS LOOK TO STICK AROUND THROUGH FRIDAY...BEFORE ANOTHER ROUND OF HIGH CLOUDS WORKS INTO THE CWA. THIS MAY INHIBIT SOME OF THE BEST RIDGE VALLEY SPLIT POTENTIAL TONIGHT. OVERALL...TEMPERATURES SHOULD/T DEVIATE MUCH FROM WHAT WAS SEEN IN THE PREVIOUS 24 HOURS. HIGHS TODAY WILL GENERALLY BE IN THE UPPER 30S AND LOW 40S...WITH OVERNIGHT LOWS TONIGHT DROPPING DOWN INTO THE UPPER 20S. WINDS AT THE SURFACE WILL REMAIN QUITE LIGHT AND VARIABLE THROUGH THE SHORT TERM...WHILE ABOVE THE CONTINUED MID LEVEL SUBSIDENCE INVERSION...THEY WILL INCREASE RAPIDLY THANKS TO A WEST TO EAST ORIENTED JET STREAK WHICH IS CURRENTLY PUSHING ALONG AND SOUTH OF KY. .LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 358 AM EST THU DEC 18 2014 A FAIRLY ACTIVE PATTERN IN STORE FOR THE EXTENDED PORTION OF THE FORECAST. THE MODELS AREA IN PRETTY GOOD AGREEMENT WITH THE LARGE SCALE UPPER LEVEL FLOW PATTERN THROUGH MID WEEK. THREE SYSTEMS ARE FORECAST TO AFFECT EASTERN KENTUCKY...THE FIRST BEING A WEAK AREA OF LOW PRESSURE THAT IS FORECAST TO FORM OVER THE SOUTHERN PLAINS AND THEN PROGRESS EASTWARD ACROSS THE GULF COAST FRIDAY NIGHT THROUGH SATURDAY NIGHT. THE SECOND AND THIRD WEATHER SYSTEMS TO AFFECT THE REGION...SHOULD THE MODELS PAN OUT...WOULD COME MONDAY THROUGH WEDNESDAY OF NEXT WEEK. THE FIRST OF THESE LATE PERIOD SYSTEMS IS PROGGED TO ORIGINATE OVER THE GULF OF MEXICO AND MOVE UP THE EASTERN SLOPES OF THE APPALACHIAN MOUNTAINS MONDAY AND MONDAY NIGHT. THE SECOND WEATHER SYSTEM IN THIS SCENARIO IS FORECAST TO TAKE SHAPE OVER THE NORTHERN PLAINS TO BEGIN THE NEW WORK WEEK. THIS SECOND SYSTEM WOULD COME IN THE FORM OF A LARGE SCALE AND MUCH DEEPER TROUGH THAN EITHER OF THE SOUTHERN STREAM SYSTEMS. THIS AREA OF LOW PRESSURE WOULD PROVIDE THE SOURCE OF COLD AIR THAT COULD BRING SUB FREEZING TEMPERATURES AND SNOW NEXT WEDNESDAY NIGHT. THE UNCERTAINTY WITH THIS WEEKENDS WEATHER WILL REVOLVE AROUND HOW MUCH COLD AIR WILL BE ABLE TO FILTER INTO THE AREA AS THE SOUTHERN PLAINS LOW MAKES ITS NORTHEASTERN TURN FRIDAY NIGHT. BASED ON THE LATEST MODEL SOUNDINGS AND TIME HEIGHTS...THERE IS SOME UNCERTAINTY AS TO HOW FAR SOUTH THE COLD AIR WILL PENETRATE FRIDAY NIGHT INTO SATURDAY MORNING. BASED ON THIS...DECIDED TO CONFINE ANY ACCUMULATING SNOW TO THE AREA NORTH OF THE MOUNTAIN PARKWAY BETWEEN 6 AND 12Z FRIDAY NIGHT. THE SNOW SHOULD THEN TRANSITION TO A RAIN SNOW MIX EARLY SATURDAY MORNING...AND THEN TO ALL RAIN BY EARLY SATURDAY AFTERNOON. ANY SNOW ACCUMULATIONS THAT DO OCCUR WOULD LIKELY BE CONFINED TO GRASSY AREAS AND ELEVATED SURFACES. OUR FAR EASTERN COUNTIES COULD SEE ANOTHER SHOT OF RAIN SNOW MIX OR ALL SNOW FOR A BRIEF PERIOD SATURDAY NIGHT AS THE LOW EXITS THE AREA AND WINDS SHIFT TO THE NORTH NORTHEAST. A WEAK RIDGE OF HIGH PRESSURE ALOFT SHOULD PROVIDE A BRIEF RESPITE FROM THE WINTRY WEATHER LATE SATURDAY NIGHT THROUGH MID MORNING ON SUNDAY. THE MODELS ONCE AGAIN OFFER UP SOME UNCERTAINTY AS TO EXACTLY WHEN PRECIPITATION ONSET WILL BE ON SUNDAY...WITH THE GFS MODEL HOLDING OFF A LOT LONGER THAN THE ECMWF. BASED ON THIS...WENT WITH A BLEND BETWEEN THE TWO MODELS FOR PRECIP ONSET ON SUNDAY ACROSS OUR EASTERN COUNTIES...WITH LIGHT RAIN AFFECTING THE SOUTHEASTERN TWO THIRDS OF THE AREA AS MOISTURE FROM THE GULF LOW BEGINS TO MOVE NORTHWARD INTO THE AREA. THE BETTER SHOT OF PRECIPITATION WILL COME FROM MONDAY NIGHT THROUGH WEDNESDAY EVENING...AS A MUCH STRONGER AND WETTER WEATHER SYSTEM DIVES OUT OF THE NORTHERN PLAINS AND PHASES WITH WHAT EVER ENERGY IS LEFT OVER FROM THE GULF OF MEXICO WEATHER SYSTEM. MOST OF THE PRECIPITATION WITH THIS THIRD WEATHER SYSTEM LOOKS TO BE IN THE FORM OF RAIN BASED ON THE TEMPERATURE PROFILES SEEN IN THE LATEST MODEL DATA. COULD SEE SOME MORE SNOW WITH THIS FINAL WEATHER SYSTEM AS WINDS SHIFT TO THE WEST AND NORTHWEST BEHIND THE LOW AS IT MOVES INTO NEW ENGLAND AND COLDER AIR SPILLS INTO THE REGION. THE OTHER WEATHER CONCERN OF NOTE FOR THE END OF THE EXTENDED PERIOD WILL BE WINDS...PARTICULARLY FROM WEDNESDAY ONWARD. THE MODELS ALL AGREE THAT A WELL DEVELOPED PRESSURE GRADIENT WILL ACCOMPANY THE GREAT PLAINS WEATHER SYSTEM AS IT MOVES EAST. SUSTAINED WEST TO NORTHWEST WINDS OF 10 TO 15 MPH...WITH GUSTS OF 20 TO 25 MPH...WILL NOT BE OUT OF THE QUESTION. TEMPERATURES THROUGHOUT THE EXTENDED PERIOD LOOK TO BE AT OR SLIGHTLY ABOVE NORMAL FROM SUNDAY THROUGH WEDNESDAY. THE WARMEST STRETCH DURING THAT TIME WOULD BE MONDAY AND TUESDAY...AS WINDS SHIFT TO THE SOUTH AHEAD OF THE MID WEEK WEATHER SYSTEM. HIGHS ON EACH OF THOSE DAYS ARE EXPECTED TO TOP OUT IN THE UPPER 40S AND LOWER 50S RESPECTIVELY. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING) ISSUED AT 656 AM EST THU DEC 18 2014 AN UPPER LEVEL DISTURBANCE IS BRINGING MOISTURE ACROSS SOUTHERN KENTUCKY THIS MORNING. SURFACE HIGH PRESSURE...HOWEVER...IS MAKING IT HARD FOR THE MAJORITY OF THIS MOISTURE TO MAKE IT THROUGH THE LAYER OF DRY AIR AT THE SURFACE. IT IS POSSIBLE FOR KSME AND KLOZ TO SEE A FEW SPURTS OF SNOW AND POSSIBLY SLEET AS WE HEAD INTO THE MID MORNING. HOWEVER...THE LIGHT AND ISOLTED NATURE OF THIS PRECIP IS NOT LIKELY TO CAUSE VIS RESTRICTIONS...SO CONTINUED TO KEEP MENTION OF PRECIP OUT OF THE TAF. FOR THE REMAINING TAF SITES...LESS INFLUENCE FROM THIS UPPER LEVEL DISTURBANCE HAS LEFT HIGH PRESSURE TO RULE THE SKIES. THIS HAS RESULTED IN A STRONG SUBSIDENCE INVERSION...TRAPPING LOW LEVEL MOISTURE AND CREATING A MVFR CIG DECK. EXPECT BOTH THE LLVL CLOUD DECK...AND ANY REMAINING PRECIP CHANCES...TO DISSIPATE AS WE HEAD INTO THE LATE MORNING/EARLY AFTERNOON. WHILE WINDS WILL REMAIN LIGHT NEAR THE SURFACE...A WEST TO EAST ORIENTED UPPER LEVEL JET STREAK WILL KEEP STRONG WESTERLY WIND FLOW ABOVE THE HIGH PRESSURE INVERSION /AROUND 6K FT AGL/ FOR THE NEXT 24 HOURS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...JMW LONG TERM...AR AVIATION...JMW

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