Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 040528 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 128 AM EDT TUE AUG 4 2015 .UPDATE...
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ISSUED AT 1243 AM EDT TUE AUG 4 2015 SURFACE ANALYSIS THIS EVENING FEATURES A CLUSTER OF SHOWERS AND THUNDERSTORMS AHEAD OF A WEAK APPROACHING COLD FRONT TONIGHT. THIS ACTIVITY WAS ABLE TO TAP INTO SOME INSTABILITY FROM THE DAY AND AS THE FRONT APPROACHES WITH SOME...THOUGH WEAK FORCING...SOME OF THE ELEVATED INSTABILITY MAY BE TAPPED INTO. THEREFORE...WILL KEEP AT LEAST A LEAST CHANCE TO LOW CHANCE POPS THROUGH THE NIGHT INTO THE MORNING HOURS. THIS IS EVIDENT DUE TO THE FACT OF CONTINUED ISOLATED CELLS DEVELOPING ALONG THE OUT FLOW FROM THE STORMS UP NORTH AND EVEN BEHIND THE LINE OF STORMS AHEAD OF THE FRONT ITSELF. UPDATED THE FORECAST INTO THE DAY AS WELL WITH THE FRONT BEGINNING TO STALL AND BECOME A FOCUS FOR CONVECTION INTO THE DAY TOMORROW AND AFTERNOON. THOUGH WOULD THINK THE LACK OF FORCING AND SLOWLY BEING A SITUATION WHERE CONVECTION WILL RELY ON THE DAYS INSTABILITY...WENT WITH SLIGHT CHANCE TO LOW CHANCE...MAINLY ALONG THE HIGH TERRAIN IN THE EAST. SO WOULD EXPECT A GRADUAL SLOW DOWN IN ACTIVITY THROUGH DAWN BEFORE RAMPING UP AGAIN THROUGH THE DAY. A NEW ZFP HAS BEEN SENT AND GRIDS FRESHENED UP AND SENT SENT TO NDFD. UPDATE ISSUED AT 1058 PM EDT MON AUG 3 2015 SEVERAL STRONG TO SEVERE THUNDERSTORMS HAVE BEEN MOVING ACROSS THE NORTHERN PART OF THE FORECAST AREA SINCE AROUND 830...DOWNING TREES AND DUMPING HEAVY RAIN THAT HAS LEAD TO MAJOR FLOODING ISSUES IN ROWAN AND MONTGOMERY COUNTIES. A HASTILY PREPARED ZONE FORECAST UPDATE HAS JUST BEEN SENT OUT...FOCUSING ON GETTING THE ONGOING SHOWERS AND STORMS THROUGH OUR FORECAST AREA OVERNIGHT. UPDATE ISSUED AT 729 PM EDT MON AUG 3 2015 NO MAJOR CHANGES WERE MADE TO THE FORECAST AT THIS TIME. WILL CONTINUE TO MONITOR SHOWER AND STORM ACTIVITY THAT IS ONGOING ACROSS SOUTHERN OHIO AND NORTH CENTRAL KENTUCKY TO SEE HOW MUCH OF THIS MAKES IT INTO EASTERN KENTUCKY THIS EVENING. WILL ALSO CONTINUE TO LOOK FOR NEWLY FORMED SHOWERS AND STORMS AS OUTFLOW FROM EXISTING STORMS PROPAGATE SOUTH INTO OUR AREA. AT THE VERY LEAST WILL EVENTUALLY NEED TO REMOVE SOME OUTDATED WORDING FROM THE ZONE FORECAST TEXT PRODUCT.
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&& .SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT) ISSUED AT 319 PM EDT MON AUG 3 2015 THE OUTFLOW BOUNDARY FROM THE EARLY MORNING MCS TO OUR NORTH MOVED ACROSS AND OUT OF THE FORECAST AREA HELPING TO STABILIZE MUCH OF EASTERN KY. DESTABILIZATION HAS BEEN OCCURRING SLOWLY...BUT TO THIS POINT THE INSTABILITY AXIS HAS REMAINED WELL TO THE NORTHWEST OF THE AREA. THE 18Z MESOANALYSIS SHOWS MLCAPE FROM 2500 TO 3000 J/KG FROM WESTERN KY INTO CENTRAL INDIANA. AT THIS TIME CONVECTION IS BEGINNING TO DEVELOP OVER CENTRAL INDIANA OUT AHEAD OF A COLD FRONT THAT IS OVER NW INDIANA. THIS CONVECTION SHOULD DEVELOP FURTHER OVER THE NEXT COUPLE OF HOURS AND IT IS POSSIBLE THAT AT LEAST THE NORTHERN PART OF THE FORECAST AREA COULD SEE A FEW THUNDERSTORMS THIS EVENING. HOWEVER LATEST SHORT RANGE GUIDANCE TRENDS MAKE THIS A LOW CONFIDENCE PRECIPITATION FORECAST...AND THUS WILL KEEP PROBABILITIES FOR ANY SHOWERS AND THUNDERSTORMS LOW FOR THE OVERNIGHT PERIOD. THE BEST CHANCE...BUT STILL ONLY A 30 PERCENT PROBABILITY WILL BE PLACED IN THE NORTHEAST TWO THIRDS OF THE FORECAST AREA. THE WEAK COLD FRONT WHICH EXTENDS FROM LAKE HURON TO NORTHWEST INDIANA WILL MAKE SLOW SOUTHEAST PROGRESS TONIGHT...AND THE FRONT WILL MOVE INTO KY ON TUESDAY. HOWEVER ANY FORCING WILL REMAIN MARGINAL...AND WILL ONCE AGAIN CARRY ONLY 20 TO 30 PERCENT PROBABILITIES OF SHOWERS AND THUNDERSTORMS ON TUESDAY...BUT WITH THE SLIGHTLY HIGHER CHANCE ACROSS THE SOUTHERN PART OF THE FORECAST AREA. .LONG TERM...(WEDNESDAY THROUGH MONDAY) ISSUED AT 319 PM EDT MON AUG 3 2015 MODELS ARE SHOWING SOME SIGNIFICANT DIFFERENCES NOW IN THE STRENGTH AND TIMING OF SYSTEMS THROUGH THE REGION. IN GENERAL WE CAN EXPECT WEST SOUTHWEST FLOW THROUGH ROUGHLY THE FIRST HALF OF THE PERIOD... BEFORE UPPER LEVEL PATTERN BECOME MORE NORTHWESTERLY FOR THE REMAINDER OF THE EXTENDED. MODELS SUGGEST TWO MAIN DISTURBANCES THROUGH THE OHIO VALLEY...THE FIRST WED NIGHT...OR MORE LIKELY THU AND THE SECOND AT THE VERY END OF THE WEEK...OR POSSIBLY INTO THE WEEKEND. WHILE TIMING IS SIMILAR THE 12Z GFS IS MUCH LESS AMPLIFIED AND MORE DISORGANIZED WITH THE MID WEEK STORM SYSTEM WHEN COMPARED WITH THE 0Z ECMWF TO START OUT THE EXTENDED. A QUICK PEAK AT THE 12Z ECMWF SHOWS THAT IT HAS TRENDED TOWARDS THE GFS A BIT BUT REMAINS AMPLIFIED ENOUGH TO MAINTAIN A MORE ORGANIZED SFC SYSTEM WEDNESDAY NIGHT INTO THU. THE GFS IS CONSIDERABLY FASTER THAN THE 0Z ECMWF WITH THE SECOND MAIN DISTURBANCE TARGETING OUR AREA WITHIN THE EXTENDED WINDOW...BY 12 HOURS OR MORE AT THE END OF THE WEEK...BEGINNING OF THE WEEKEND. THE 12Z ECMWF HAS TRENDED WEAKER WITH THIS SECOND DISTURBANCE. A LOW CONFIDENCE FORECAST SUGGESTS THE BEST APPROACH IS TO RELY HEAVILY ON MODEL CONSENSUS AND GUIDANCE BLENDS UNTIL MODELS COME INTO BETTER AGREEMENT. AT THE SURFACE...UNTIL THE FIRST DISTURBANCE HAS PUSHED OFF TO OUR EAST LATE IN THE WEEK A LINGERING QUASI/STATIONARY SURFACE BOUNDARY DRAPED ACROSS THE OHIO VALLEY REGION WILL TEND TO KEEP OUR WEATHER MORE ACTIVE THAN THE PAST SEVERAL DAYS. MAIN CHALLENGE IS WHERE THIS BOUNDARY ACTUALLY SETS UP AS MODELS CONTINUE TO DISAGREE WITH SOUTHERN EXTENT OF THIS SFC FRONTAL ZONE. OVERALL CONFIDENCE IS LOW IN THE DETAILS OF SENSIBLE WEATHER THOUGH TEMPERATURES WILL MOST LIKELY BE NEAR TO SLIGHTLY BELOW NORMAL IN GENERAL...WITH A SLIGHTLY ELEVATED RISK OF POPS WHEN COMPARED WITH NORMS. && .AVIATION...
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(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 128 AM EDT TUE AUG 4 2015 SCATTERED SHOWERS AND THUNDERSTORMS FORMING AHEAD OF AN APPROACHING COLD FRONT AND FURTHER SOUTH...AN OUTFLOW FORM THE EARLIER CONVECTION OVER THE BLUEGRASS. THUS...OVER THE SOME OF THE SOUTHERN TAF SITES...HAVE MENTIONED VCTS IN THESE AREAS AS CONVECTION HAS WANED A BIT. MUCH OF THE AREA TONIGHT HAS RECEIVED A GOOD SHOT OF RAIN LEAVING A SATURATED BOUNDARY LAYER AND FOG DEVELOPMENT IS EXPECTED TONIGHT AD TOWARDS DAWN. WILL PUT SOME FIELD MINS AT THE TAF SITES WITH THE FOG LIFTING AFTER 13Z. HEADING INTO TUESDAY AFTERNOON...CONVECTION WILL AGAIN ERUPT ALONG THE STALLED BOUNDARY BUT CONVECTION SHOULD BE SPARSE AND WILL LEAVE THUNDER OUT OF THE TAFS FOR NOW. VFR CONDITIONS WILL BE EXPECTED THROUGH THE DAY WITH FOG DEVELOPING AGAIN AT THE TAF SITES TUESDAY NIGHT.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...SBH LONG TERM...RAY AVIATION...SHALLENBERGER

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