Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 250735 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 335 AM EDT SAT APR 25 2015 .UPDATE... ISSUED AT 202 AM EDT SAT APR 25 2015 WITH EXTENSIVE CLOUD COVER IN PLACE...TEMPS HAVE NOT DROPPED OFF AS QUICKLY AS WAS FORECAST. HAVE RAISED OVERNIGHT FORECAST MIN TEMPS A BIT...ESPECIALLY IN EASTERN VALLEYS. UPDATE ISSUED AT 1050 PM EDT FRI APR 24 2015 DID AN UPDATE TO FINE TUNE THE POPS AND WX THROUGH THE REST OF THE NIGHT BASED ON THE NEWEST HRRR AND NAM12 GUIDANCE AS WELL AS CURRENT RADAR/OBS. ALSO MATCHED UP THE HOURLY T AND TD GRIDS PER THE LATEST OBS AND TRENDS...WHERE A 5 DEGREE OR SO RIDGE TO VALLEY SPLIT CURRENTLY EXISTS IN THE EAST. THESE GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS...ALONG WITH THE ISSUANCE OF A FRESHENED SET OF ZONES. UPDATE ISSUED AT 745 PM EDT FRI APR 24 2015 23Z SFC ANALYSIS SHOWS HIGH PRESSURE CLINGING ON IN THE FAR EAST IN THE FACE OF AN APPROACHING AREA OF LOW PRESSURE...POISED TO BRING SVR WX TO KY LATER ON SATURDAY...FROM THE WEST. THIS WESTERN LOW/S WARM FRONT WILL SWING TOWARD THE AREA BY DAWN... AFFECTING THE FAR SOUTHWEST INITIALLY THEN LIFTING DEEPER INTO EAST KENTUCKY THROUGH MIDDAY SATURDAY. THE PCPN WILL HAVE A TOUGH TIME REACHING THE GROUND ACROSS THE AREA THROUGH THE BULK OF THE NIGHT AS THE VERY DRY LOWER ATMOSPHERE ONLY SLOWLY SATURATES... DESPITE THE HRRR/NAM12 INDICATIONS. IN THIS ENVIRONMENT...EXPECT THE EASTERN VALLEYS TO DROP OFF QUICKLY FOLLOWING SUNSET...EVEN WITH THE THIN HIGH CLOUDS NOW IN PLACE OVERHEAD. ELSEWHERE... TEMPERATURES WILL STAY UP THROUGH THE NIGHT...MUCH WARMER THAN LAST NIGHT. HAVE UPDATED THE FORECAST TO NUDGE TEMPS IN THE EASTERN VALLEYS DOWN A BIT...BUT EXPECT THEM TO MIX OUT BY DAWN AS THE AIR SATURATES AND SHOWERS PUSH OVER THIS PART OF THE STATE. IN ADDITION TO THE SEVERE THREAT FOR SATURDAY...THE LATEST MODEL RUNS CONTINUE TO INDICATE THAT THERE IS ALSO A POTENTIAL FOR EXCESSIVE RAINFALL DEPENDING ON THE TRACKS OF THE INDIVIDUAL CELLS AND/OR AN MCS TRACKING ACROSS THE CWA IN THE AFTERNOON/EVENING THAT CERTAINLY LOOKS POSSIBLE. THESE UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. && .SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT) ISSUED AT 350 PM EDT FRI APR 24 2015 CURRENT CONDITIONS ACROSS THE AREA FEATURE SURFACE HIGH PRESSURE SLOWLY SLIDING OFF TO THE EAST TODAY. MID AND UPPER LEVEL CLOUD COVER AT THIS TIME IS BEGINNING TO STREAM INTO EASTERN KENTUCKY THIS EVENING. THIS IS AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM OUT WEST OVER THE CENTRAL PLAINS. CLOUD COVER OVER THE AREA WILL LIKELY KEEP TEMPERATURES OVERNIGHT NEARLY UNIFORM WITH SOUTHERLY WARM AIR MOVING INTO THE AREA THROUGH THE NIGHT. AT THIS TIME OVERNIGHT...THE SURFACE LOW SLIDES EAST AS A WARM FRONT DEVELOPS IN THE LOWER MS VALLEY AND MOVING NORTHEAST. THIS WILL BRING SHOWERS INTO EASTERN KENTUCKY BY MIDNIGHT OR SHORTLY AFTERWARD. HEADING INTO THE PREDAWN HOURS SATURDAY MORNING...THE MAIN SURFACE LOW BEGINS TO MOVE INTO THE MID MS RIVER VALLEY AND INTO THE MIDWEST WITH SOME INSTABILITY BEGINNING TO ENTER THE SOUTHWESTERN COUNTIES AND THIS MAY LEAD TO A FEW EARLY NON SEVERE STORMS AND MAY NEED TO ADD THUNDER TO THE TONIGHT PERIOD OF THE HWO. HEADING INTO THE DAY ON SATURDAY...AFTER EARLIER RAINFALL HAS MOVED THROUGH...SOME CLEARING SKIES AND RECOVERING ENERGY AND DESTABILIZATION WILL THEN OCCUR WITH MOST UNSTABLE CAPE AROUND 1000 TO 1500 J/KG OVER SOUTHEASTERN KENTUCKY BY THE 18Z TIME FRAME. THIS ALSO WITH SOME 60 KNOT SFC TO 6KM BULK SHEAR WILL BE ENOUGH FOR SOME ROTATING STORMS TOMORROW AFTERNOON. DUE TO THIS THREAT SPC HAS PUT THE SOUTHERN AREA IN AN ENHANCED THREAT OF SEVERE WEATHER AND HAVE PUT THIS THREAT IN THE HWO AND MAY NEED AN SPS TO HIGHLIGHT THE THREAT IN DETAIL. THE ONLY THREAT THAT IS A BIT QUESTIONABLE TOMORROW WILL BE THE FLASH FLOOD THREAT. THOUGH THE LAST HEAVY RAINFALL WAS LONG ENOUGH AGO THAT MOST PLACES HAVE BEEN ALLOWED TO DRAIN AND DRY OUT. AS WELL...GREEN HAS GONE INTO FULL SWING ACROSS THE AREA ALLEVIATING THE RUNOFF POTENTIAL. HOWEVER...THE DISCRETE SUPER CELL POTENTIAL WILL ADD TO THE THREAT OF FLASH FLOODING AS WELL AS IF AN MCS DEVELOPS BY LATE IN THE EVENING ON SATURDAY. MAY NEED TO EVALUATE THIS DURING THE NEXT MODEL RUN. HEADING INTO SATURDAY EVENING...THE WARM FRONT MOVES THROUGH TO THE NORTHEAST AND THEN THE SURFACE LOW TRACKS RIGHT ACROSS EASTERN KENTUCKY WITH ANOTHER STRONG SHOT OF RAINFALL WHICH MAY BE ENOUGH TO INITIATE THE FLASH FLOOD THREAT. HAVE ADJUSTED THE QPF FOR THE 00Z TO 06Z SUNDAY NIGHT PERIOD FOR THIS RAINFALL. RAINFALL AMOUNTS WILL BE LESSENING BY 06Z TO 12Z RANGE SUNDAY NIGHT AS THE EVENT WILL BE WINDING DOWN. FOR NOW...WILL HIGHLIGHT THE SEVERE AND FLOOD THREAT IN THE HWO AND MAY NEED AN SPS TO FURTHER HIGHLIGHT THIS. THE ZFP WILL HAVE SEVERE POTENTIAL AND HEAVY RAINFALL MENTIONED AS WELL. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 335 AM EDT SAT APR 25 2015 THE MODELS WERE IN GOOD AGREEMENT IN THE EXTENDED. THE PERIOD IS SET TO BEGIN WITH A LARGE RIDGE OF HIGH PRESSURE MOVE OUT OF THE NORTH CENTRAL PLAINS AND ACROSS THE LOWER GREAT LAKES AND OHIO AND TENNESSEE VALLEY REGIONS SUNDAY NIGHT THROUGH TUESDAY. THE PATTERN IS THEN FORECAST TO CHANGE TUESDAY NIGHT AND WEDNESDAY...AS BOTH NORTHERN AND SOUTHERN STREAM WEATHER SYSTEMS MAKE THEIR WAY ACROSS THE GREAT LAKES AND GULF COAST REGIONS. THE SOUTHERN STREAM SYSTEM APPEARS TO BE THE STRONGER OF THE TWO...AND THEREFORE WOULD HAVE TO GREATER INFLUENCE ON AREA WEATHER MID WEEK. AS IT STANDS...A ROUGHLY 60 40 BLEND OF THE ECMWF AND GFS MODELS WAS USED TO CREATE THE FORECAST FROM TUESDAY NIGHT ONWARD. THE SOUTHERN STREAM TROUGH IS PROGGED TO BRING MOISTURE OFF THE GULF OF MEXICO NORTHWARD INTO CENTRAL AND EASTERN KENTUCKY WEDNESDAY AND WEDNESDAY NIGHT. AS THIS OCCURS...THE NORTHERN STREAM SYSTEM IS FORECAST TO DIVE SOUTHWARD AND PHASE WITH THE TENNESSEE VALLEY SOUTHEASTERN CONUS LOW. THE GFS DOES DIFFER SLIGHTLY FROM THE ECMWF MODEL DURING THIS PERIOD...AS ITS NORTHERN STREAM LOW PUSHES ON EASTWARD INTO NEW ENGLAND...AS OPPOSED TO PHASING WITH THE SOUTHERN SYSTEM...AS THE ECMWF IS DEPICTING. THAT BEING SAID...THIS IS WHERE THE USUALLY MORE CONSISTENT ECMWF MODEL SOLUTION WAS FAVORED. THERE WILL BE A CHANCE OF RAIN IN THE FORECAST FOR THE ENTIRE AREA FROM LATE TUESDAY NIGHT THROUGH THURSDAY NIGHT. HOWEVER...DUE TO THE DIFFERING MODEL SOLUTIONS...DECIDED TO STAY WITH SLIGHT CHANCE TO CHANCE POPS...WITH 40 BEING THE HIGH END DURING THE WET PERIOD. FRIDAY AND FRIDAY NIGHT LOOK TO BE DRY AS THE SOUTHERN STREAM WEATHER SYSTEM EXITS TO OUR EAST AND ANOTHER RIDGE OF HIGH PRESSURE BUILDS ACROSS THE SOUTHERN AND SOUTHEASTERN CONUS. TEMPERATURES NEXT WEEK WILL LIKELY BE BELOW NORMAL THROUGH THURSDAY...DUE TO THE INFLUENCE OF CLOUD COVER AND PRECIPITATION AND THE FACT THAT THIS WEEKENDS TEMPERATURES WILL ALSO REMAIN WELLBELOW NORMAL DUE WIDESPREAD CLOUD COVER AND PRECIPITATION. WHAT THIS AMOUNTS TO IS THE ATMOSPHERE WILL STARTING OFF BEHIND THE EIGHT BALL TO START THE WEEK TEMPERATURE WISE...MAKING IT DIFFICULT FOR THINGS TO WARM UP AS MUCH AS NORMAL DUE TO THE SHORT BREAK BETWEEN WEATHER SYSTEMS. HIGHS ON FRIDAY SHOULD BE RIGHT AROUND NORMAL ACROSS THE ENTIRE AREA. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT 202 AM EDT SAT APR 25 2015 VFR CONDITIONS WERE PRESENT AT TAF ISSUANCE...BUT WILL DEGRADE TO MVFR FROM SW TO NE BETWEEN ABOUT 06Z AND 14Z AS RAIN DEVELOPS. IFR IS ALSO EXPECTED AT TIMES THROUGH EARLY AFTERNOON. STEADY PRECIPITATION WILL TAPER OFF FROM SW TO NE DURING THE LATE MORNING AND EARLY AFTERNOON...AND WILL BE REPLACED BY SCATTERED SHOWERS AND THUNDERSTORMS. THEY WILL BECOME MORE NUMEROUS LATE IN THE DAY AND THIS EVENING. SOME LOCATIONS MAY DESCEND BACK TO IFR WITH THE SHOWERS AND STORMS THIS EVENING. SOME OF THESE STORMS COULD PRODUCE HAIL AND HIGH WINDS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...SHALLENBERGER LONG TERM...AR AVIATION...HAL

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