Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 220529 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 129 AM EDT TUE JUL 22 2014 .UPDATE... ISSUED AT 130 AM EDT TUE JUL 22 2014 UPDATED FOR THE CURRENT TEMPERATURES TO REFLECT WHERE SOME CLOUD COVER LINGERS...TEMPS ARE DROPPING A BIT SLOWER DUE TO INSULATION AND WHERE THEY ARE DROPPING A BIT FASTER SUCH AS THE BLUEGRASS WHERE THAT AREA HAS CLEARED OUT. OTHERWISE THE FORECAST REMAINS ON TRACK. A FEW SHOWERS MAY STILL POP UP IN THE SOUTHEAST AND WILL LEAVE THE SLIGHT CHANCE POPS THERE. HAVE SENT THE GRIDS TO NDFD AND WEB SERVERS. UPDATE ISSUED AT 1120 PM EDT MON JUL 21 2014 AN OUTFLOW BOUNDARY IS CURRENTLY MOVING IN FROM THE SOUTHEAST. A FEW SHOWERS ARE HANGING ON IN THE WAKE OF THIS PASSING FEATURE...AND WILL HOLD ONTO A FEW SHOWERS FOR ANOTHER HOUR...BEFORE DRY WEATHER ENSUES FOR THE REST OF THE NIGHT. THE REST OF THE FORECAST REMAINS ON TRACK AND HAVE JUST FRESHENED UP THE HOURLY TEMPERATURES AND DEW POINTS ACCORDING TO THE LATEST TRENDS IN OBSERVATIONS. UPDATE ISSUED AT 838 PM EDT MON JUL 21 2014 THE FORECAST REMAINS ON TRACK. ISOLATED CONVECTION IS STILL DOTTING THE AREA...ESPECIALLY ALONG THE SOUTHEAST TERRAIN. EXPECT A GRADUAL WEAKENING TREND THROUGH MIDNIGHT. DID DIAL BACK THE POPS A BIT FURTHER NORTH SOONER GIVEN THE TREND OF DIMINISHING CU. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT) ISSUED AT 415 PM EDT MON JUL 21 2014 AN UPPER LEVEL RIDGE WAS CENTERED OVER THE SOUTHERN ROCKIES AND SOUTHERN PLAINS REGION...WITH THE RIDGING EXTENDING TOWARD THE MID MS AND LOWER OH VALLEY REGION. ANOTHER RIDGE WAS CENTERED OFF THE SOUTHEASTERN U.S. COAST. AN UPPER LEVEL TROUGH/WEAK UPPER LEVEL LOW WAS OVER THE SOUTHEASTERN STATES. MEANWHILE A TROUGH WAS DEPARTING THE NORTHEASTERN U.S. A COUPLE OF SHORTWAVES ARE WORKING ALONG THE US/CANADIAN BORDER/NORTHERN ROCKIES REGION WHILE ANOTHER SHORTWAVE IS ROTATING AROUND AN UPPER LEVEL LOW OVER THE HUDSON BAY REGION. A WARM AND RATHER MOIST AIR MASS IS IN PLACE ACROSS THE REGION...HOWEVER...MID LEVEL DRY AIR AND LIMITED UPPER LEVEL SUPPORT IS LIMITING COVERAGE THUS FAR. THROUGH THE PERIOD...THE UPPER LEVEL LOW IS EXPECTED TO MEANDER TO THE MS DELTA REGION. MEANWHILE THE UPPER LEVEL RIDGE WILL AMPLIFY ACROSS THE ROCKIES AND INTO PARTS OF CANADA WHILE A TROUGH BEGINS TO DEVELOP OVER THE EASTERN CANADA AND THE GREAT LAKES AS THE SHORTWAVES MOVE TOWARD THE WESTERN GREAT LAKES AND MERGE WITH A SHORTWAVE ROTATING FROM CENTRAL CANADA INTO EASTERN CANADA. AS THIS OCCURS... A SFC LOW WILL TRACK FROM THE DAKOTAS TO NORTHERN QUEBEC. THE TRAILING COLD FRONT WILL APPROACH THE OH VALLEY LATE IN THE PERIOD. SOME OF THE NEAR TERM MODELS STILL INDICATE AT LEAST SOME ISOLATED SHRA/TSRA COULD DEVELOP THROUGH THIS EVENING. THE CURRENT CU FIELD IS NOT ALL THAT IMPRESSIVE AND COVERAGE MAY BE MORE LIMITED THAN THAT. POPS WERE LOWERED FOR LATE THIS AFTERNOON/EVENING COMPARED TO THE PREVIOUS FORECAST WITH 30 PERCENT ACROSS THE HIGH TERRAIN AND JUST ISOLATED OVER THE REGION OF THE AREA. A WEAK DISTURBANCE ROTATING AROUND THE SOUTHEAST UPPER LOW COULD LEAD TO THE THREAT OF CONVECTION FOR A LITTLE WHILE AFTER 0Z NEAR THE VA BORDER. OTHERWISE...OVERNIGHT... WITH A WEAK PRESSURE GRADIENT IN PLACE AND SKIES MOSTLY CLEAR TO PARTLY CLOUDY ALONG WITH THE MID TO UPPER 60S DEWPOINTS EXPECTED...FOG SHOULD AGAIN FORM. THE FOG MAY AGAIN BECOME DENSE IN THE RIVER VALLEY LOCATIONS. TUESDAY INTO TUESDAY NIGHT...THE RIDGE SHOULD EXTEND EAST INTO THE OHIO VALLEY...BUT THE SOUTHERN OR SOUTHEASTERN COUNTIES WILL BE CLOSER TO THE NORTHEASTERN EDGE OF THE SOUTHEASTERN U.S. UPPER LOW. THERE SHOULD AGAIN BE CONSIDERABLE CU FORMATION ON TUE...BUT SOME MID LEVEL WARM AIR MAY LINGER...AND AGAIN LIMIT CONVECTION. THE DIFFERENTIAL HEATING OVER THE HIGH TERRAIN OR PERHAPS ON THE OUT EDGE OF SOME OF THE CLOUD COVER OVER THE SOUTHEAST COULD BE A TRIGGER FOR CONVECTION. IN ADDITION...A WEAK DISTURBANCE MAY ROTATE AROUND THE UPPER LOW TOWARD THE APPALACHIANS. THE MODEL CONSENSUS IS FOR HIGHER CHANCES AND BETTER COVERAGE FOR CONVECTION OVER THE SOUTH AND SOUTHEAST. WINDS SHOULD AGAIN BE RATHER LIGHT ON TUE NIGHT AND WITH A MOIST AIR MASS IN PLACE...PATCHY POSSIBLY DENSE RIVER VALLEY FOG IS AGAIN ANTICIPATED. .LONG TERM...(WEDNESDAY THROUGH MONDAY) ISSUED AT 335 PM EDT MON JUL 21 2014 THE MID TERM WILL FOCUS AROUND A SURFACE COLD FRONT MOVING FROM NW TO SE ACROSS THE REGION. WINDS FLOWING SOUTHERLY UP UNTIL THIS POINT WILL BEGIN TO SWITCH TO A MORE WRLY DIRECTION JUST AHEAD OF THE FRONTAL PASSAGE. STILL...MOIST AND UNSTABLE AIR ACROSS THE REGION...AS WELL AS THE INCOMING LIFTING SOURCE WILL BE ENOUGH TO PRODUCE WIDESPREAD SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE REGION DURING THE DAYTIME HOURS WEDNESDAY. WITH CAPES WELL ABOVE 2000 J/KG AFTER 12Z...AND GOOD MID LEVEL DRY AIR...COULD BE A GOOD SCENARIO FOR SOME DECENT CONVECTION. MODELS ARE ALL IN FAIRLY GOOD AGREEMENT ABOUT THE ONSET OF PRECIP BETWEEN 15 AND 18Z IN THE NORTHERN COUNTIES...WITH SOME DIURNAL SCATTERED CONVECTION POPPING UP ACROSS EASTERN KY AFTER 12Z AHEAD OF THE MAIN LINE. AS THE FRONT SLOWLY TRAVERSES KY...EXPECT PRECIP TO LINGER INTO THE OVERNIGHT HOURS WEDNESDAY NIGHT AND INTO THE DAY THURSDAY. LOSS OF MID LEVEL DRY AIR OVERNIGHT WEDNESDAY NIGHT WILL CUT DOWN ON SOME OF THE BEST CONVECTION AND HAIL POTENTIAL...BUT EXPECT IT TO RETURN AGAIN BY THURSDAY AND CONTINUE INTO THE OVERNIGHT HOURS THURSDAY NIGHT. BY FRIDAY...THE FRONT WILL FINALLY EXIT TO OUR SE. THOUGH SOME UPSLOPE CONVECTION MAY LINGER IN THE FAR SE...OVERALL DRIER AIR SHOULD FILTER IN AND CUT OFF ANY REMAINING PRECIP CHANCES DURING THE DAY FRIDAY. TEMPS WEDNESDAY LEADING INTO THE FRONTAL PASSAGE WILL BE QUITE WARM AND HUMID...WITH HIGHS TIPPING 90 DEGREES IN SOME LOCATIONS ACROSS EASTERN KY. BY THURSDAY HOWEVER...COOLER AIR WILL BEGIN FILTERING IN THANKS TO A SURFACE HIGH PRESSURE TO OUR NORTH...WITH HIGHS ONLY EXPECTED TO REACH AROUND 80. FOR THE REMAINDER OF THE EXTENDED...A STRONG RIDGE OVER THE SW CONUS...AND A TROUGH OVER THE EASTERN CONUS WILL BE THE MAIN PLAYERS IN OUR WEATHER. ALTHOUGH THE TROUGH WILL WORK TO BECOME LESS AMPLIFIED BY LATE THE PERIOD...EXPECT SEVERAL SHORTWAVES TO RIDE ALONG THE TROUGH AND BRING PRECIP CHANCES TO THE OHIO RIVER VALLEY REGION. THE FIRST OF THESE WILL BRING SHOWERS AND THUNDERSTORMS TO EASTERN KY BY SATURDAY AFTERNOON/NIGHT. CHANCES SHOULD THEN CONTINUE THROUGH THE REMAINDER OF THE PERIOD. TEMPS WILL SLOWLY RISE BACK INTO THE MID 80S WITH HIGHER HUMIDITY VALUES BY THE WEEKEND...THEN WILL COOL SLIGHTLY AS ANOTHER COLD FRONT ACCOMPANIES THE PRECIP CHANCES SUNDAY NIGHT/MONDAY. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 130 AM EDT TUE JUL 22 2014 WITH CLOUD COVER HANGING TOUGH OVER THE AREA AND WEAK SOUTHEAST FLOW...FOG DEVELOPMENT SHOULD BE A BIT MORE LESS THAN THE PREVIOUS NIGHT...ESPECIALLY WITH SOME GREATER DEW POINT DEPRESSIONS TONIGHT. LESS RAIN FELL OVER THE AREA THAN THE PREVIOUS NIGHT AS WELL. HAVE GONE WITH MAINLY VFR AT SME AND JKL AND SOME IFR AT SJS AND MVFR AT LOZ. HEADING INTO TODAY...UNEXPECTED MID LEVEL WARMING WILL KEEP THUNDERSTORMS MORE ISOLATED ACROSS THE AREA. WITH THIS HAVE DECIDED TO REMOVE THUNDER FROM THE TAFS AND GO WITH A LOW CONFIDENCE...THOUGH THERE WILL STILL BE SOME STORMS THIS AFTERNOON BUT LITTLE CHANCE OF A CELL MOVING OVER A TAF SITE. WINDS WILL REMAIN LIGHT THROUGH THE PERIOD WITH A WEAK SOUTHEAST DIRECTION. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...JP LONG TERM...JMW AVIATION...SHALLENBERGER

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