Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 290811 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 411 AM EDT WED JUL 29 2015 .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 411 AM EDT WED JUL 29 2015 ISOLATED SLOW MOVING SHOWERS HAVE PERSISTED DURING THE NIGHT IN THE SOUTHEAST PART OF THE FORECAST AREA. FORECAST SOUNDINGS SHOW THAT SOME ADDITIONAL DEVELOPMENT CAN NOT BE RULED OUT THIS MORNING...BUT THE PROBABILITY AT ANY GIVEN LOCATION IS LOW. ADDITIONAL DEVELOPMENT OF SHOWERS/THUNDERSTORMS IS MORE PROBABLE BY THIS AFTERNOON AS HEATING OCCURS. MOST OF THEM SHOULD DIE OUT AGAIN IN THE EVENING WITH LOSS OF HEATING. A COLD FRONT WILL PASS LATE TONIGHT AND THURSDAY MORNING. A FEW SHOWERS MAY LINGER ALONG AND AHEAD OF THE FRONT IN THE SOUTHEAST PART OF THE AREA ON THURSDAY MORNING. HOWEVER...DRIER AIR ALOFT AND A POST FRONTAL INVERSION WILL PUT AN END TO ANY LINGERING SHOWERS...WITH MOST OF THURSDAY BEING DRY. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 354 AM EDT WED JUL 29 2015 WE WILL BE IN A POST FRONTAL REGIME TO START OFF THE EXTENDED FORECAST AT 0Z FRIDAY. SURFACE HIGH PRESSURE WILL CONTINUE TO TAKE HOLD THROUGH THE DAY FRIDAY WITH SLIGHTLY COOLER NRLY WINDS AT THE SURFACE. MEANWHILE...A STRONG UPPER LEVEL LOW WILL BECOME NEARLY STATIONARY ACROSS HUDSON BAY...ROTATING AROUND THE BAY FROM FRIDAY THROUGH AT LEAST MONDAY. THIS WILL KEEP A LONGWAVE TROUGHING PATTERN ACROSS MUCH OF THE MIDWEST AND EASTERN CONUS...CONTINUING THE NW FLOW REGIME ACROSS THE OHIO RIVER VALLEY. THIS NW FLOW WILL PROVIDE THE PERFECT SCENARIO FOR SHORTWAVES TO TRACK SE ALONG THE TROUGH AND INTO THE OHIO VALLEY AS IT ROUNDS THE BASE OF THE TROUGH. HOWEVER...HIGH PRESSURE WILL HAVE HOLD AT THE SURFACE. THE QUESTION THROUGHOUT THE EXTENDED IS WHETHER OR NOT THIS HIGH PRESSURE WILL BE STRONG ENOUGH TO SWAY THE IMPACT OF THESE SHORTWAVES AS THEY MOVE THROUGH EASTERN KY. THE FIRST OF THESE SHORTWAVES WILL MOVE THROUGH SATURDAY INTO SUNDAY. AS OF 0Z FRIDAY...THE ACCOMPANYING SURFACE COLD FRONT IS POSED TO BE LOCATED ACROSS THE NORTHERN PLAINS AND UPPER GREAT LAKES REGION...AND WILL SHIFT SOUTHWARD THROUGHOUT THE DAY FRIDAY AS THE SHORTWAVE NEARS. HOWEVER...THIS BOUNDARY WILL BE MOISTURE DEPRIVED AND FAIRLY WEAK. LATEST MODELS ARE STILL SHOWING SOME DISAGREEMENT ON IF THIS BOUNDARY WILL BE ABLE TO SUSTAIN PRECIPITAL MOISTURE AS IT MOVES INTO THE OHIO RIVER VALLEY. JUST LIKE YESTERDAY...THE GFS IS POINTING TOWARDS A FEW SCATTERED SHOWERS MAKING IT INTO THE CWA...WHILE THE ECMWF IS KEEPING US DRY. MEANWHILE...DESPITE THE PLAN VIEW GFS OUTPUT...THE GFS FORECAST SOUNDINGS ARE ONLY POINTING AT A NARROW WINDOW OF MID LEVEL MOISTURE WITH ABUNDANT DRY AIR NEAR THE SURFACE. THIS IS MORE CHARACTERISTIC OF SOME SCT TO BKN CLOUD COVER RATHER THAN RAINFALL. AS SUCH...WILL CONTINUE TO TREND TOWARD THE DRIER ECMWF. THE NEXT SHORTWAVE AND SURFACE BOUNDARY WILL MOVE THROUGH TUESDAY INTO WEDNESDAY AS WE FINISH OUT THE 7 DAY FORECAST. GRANTED...THIS IS FAR OUT IN THE FORECAST...BUT MODELS ARE IN SURPRISINGLY GOOD AGREEMENT IN THE UPPER LEVELS...SO CONFIDENCE IS A BIT HIGHER. THIS PARTICULAR UPPER LEVEL SHORTWAVE WILL SHOW SIGNIFICANT DIGGING AS IT NEARS THE OHIO VALLEY REGION...LENDING TO A STRONGER SURFACE BOUNDARY. IF THIS PROVES TO BE TRUE...WE MAY SEE OUR NEXT BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS DURING THIS TIME. AS FOR TEMPERATURES... THE POST FRONTAL CONDITIONS AND DRIER NW FLOW WILL BRING IN SLIGHTLY COOLER TEMPERATURES TO START OFF FRIDAY. HOWEVER...STRONG SURFACE HIGH PRESSURE IN PLACE AND CLEAR SKIES WILL PROMOTE MAXIMUM DAYTIME RADIATION...SO THE TEMP DROP WILL NOT BE THAT GREAT...STILL MAINTAINING LOW TO MID 80S. PERHAPS MORE NOTICEABLE THAN THE SLIGHT CHANGE IN TEMPERATURES WILL BE THE DECREASE IN HUMIDITY...AS LIGHT WINDS AT THE SURFACE AND NW FLOW ALOFT WILL PROMOTE LOWER RH VALUES. AS HIGH PRESSURE REMAINS IN PLACE THROUGH MUCH OF THE EXTENDED...EXPECT TEMPS TO GRADUALLY WARM A DEGREE OR TWO EACH DAY...STAYING IN THE MID 80S THROUGH THE WEEKEND AND INTO NEXT WEEK. MEANWHILE...MAXIMUM RADIATIONAL COOLING DURING THE OVERNIGHT WILL KEEP OVERNIGHT LOWS IN THE LOW TO MID 60S THROUGH THE BEGINNING OF NEXT WEEK. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT) ISSUED AT 209 AM EDT WED JUL 29 2015 CONDITIONS VARIED WIDELY AT THE START OF THE PERIOD. HOWEVER...THE TREND WILL BE FOR WORSENING CONDITIONS...WITH A DESCENT TO LIFR OR VLIFR EXPECTED FOR MOST PLACES BEFORE DAWN. THERE WERE STILL SOME SLOW MOVING SHOWERS OVER THE SOUTHEAST PART OF THE STATE. FORECAST SOUNDINGS SHOW A POTENTIAL FOR THEM THROUGH THE EARLY MORNING HOURS...BUT WHERE AND WHEN THEY WILL DEVELOP IS TOO UNCERTAIN TO FORECAST. FOG AND ASSOCIATED LOW CLOUDS WILL LIFT AND DISSIPATE AFTER SUNRISE...GIVING WAY TO LARGELY VFR BY LATE MORNING. HOWEVER... THE DAYTIME WARMING SHOULD ALSO LEAD TO ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORM DEVELOPMENT BY AFTERNOON. THEY WILL BRING LOCALIZED IFR. THE SHOWERS AND THUNDERSTORMS SHOULD THEN LARGELY DIMINISH IN THE EVENING WITH LOSS OF HEATING. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...HAL LONG TERM...JMW AVIATION...HAL

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