Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 231130 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 730 AM EDT WED JUL 23 2014 .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 342 AM EDT WED JUL 23 2014 SURFACE ANALYSIS ACROSS THE REGION AS OF 07Z FEATURE MOSTLY CLEAR SKIES WITH SOME INCREASING CLOUD COVER OVER THE SOUTHEAST AS SOUTHERLY MOIST FLOW CONTINUES TO MOVE INTO THE AREA. THIS IS AIDED BY HIGH PRESSURE CENTERED OVER THE CAROLINAS. WITH DEW POINTS IN THE LOWER 70S ACROSS MUCH OF THE AREA AND TEMPS ONLY DROPPING TO AROUND 70 FOR LOWS...MUGGY CONDITIONS WILL CONTINUE INTO DAWN AS WELL WITH SOME FOG DEVELOPMENT IN THE VALLEYS. THIS FOG SHOULD DISSIPATE AS CLOUD COVER INCREASES DURING THE MORNING HOURS. HEADING INTO THE DAY...MODELS CONTINUE TO SHOW THE CLOSED LOW WILL CONTINUE TO MEANDER ALONG THE LA/MS GULF COAST WITH A TROUGH AXIS EXTENDING INTO THE CENTRAL APPALACHIANS AND WILL ASSIST IN SOME EARLY DEVELOPMENT TODAY OF SOME SHOWERS AND THUNDERSTORMS. THIS WILL STILL BE HINDERED WITH SOME MID LEVEL WARM AIR BUT THE CAP SHOULD BECOME BUSTED IN SOME AREAS ALONG THE COUNTIES BORDERING VIRGINIA. MEANWHILE...THE MUCH ANTICIPATED COLD FRONT WILL BEGIN TO IMPACT THE AREA INTO THIS AFTERNOON. THE INCREASED FORCING AND SOUTHWEST FLOW WILL ALLOW FOR INCREASED DEVELOPMENT DURING THE 18Z TO 00Z TIME FRAME THIS AFTERNOON INTO THE EVENING. MODEL SOUNDINGS AGREE WITH A DETERIORATING CAP THROUGH THE AFTERNOON...INCREASED LIFT...AND PWATS IN THE 1.6 INCH TO 1.8 INCH RANGE WILL RAISE SOME CONCERN FOR SOME CELLS WITH HEAVY RAINFALL AND A FEW DOWN BURSTS ACROSS THE AREA. ALSO THERE IS STILL A 5% SEVERE RISK ACROSS THE AREA THIS AFTERNOON AND INTO THE EVENING ISSUED BY SPC. SO WILL MENTION SOME STRONG STORMS IN THE HWO WITH SOME HEAVY RAIN POTENTIAL AND POSSIBLY AN ISOLATED DAMAGING WIND FROM A DOWN BURST. WILL KEEP LIKELY POPS BEGINNING THIS AFTERNOON AND INTO THE EVENING CENTERED AROUND THE FORCING FROM THE FRONT ITSELF. SINCE IT IS POSSIBLE THAT WITH THE MORNING CAP...THERE MAY NOT BE ANY DEVELOPMENT AT ALL. HEADING INTO TONIGHT...ASSISTED BY THE FRONT...PRECIP WILL CONTINUE INTO TONIGHT WITH DIMINISHING CHANCES TOWARDS DAWN AS INSTABILITY DECREASES. THE FORECAST CHALLENGE FOR THE PERIOD WILL BE HEADING INTO LATE TONIGHT AND THURSDAY. MODELS HAVE THE FRONT PUSHING THROUGH BUT THE HIGH PRESSURE TO THE EAST MAY HINDER THE APPROACH OF THE FEATURE SO BRINGING AN END TO PRECIP MAY BE A BIT LATER ON THE DAY THURSDAY SO WILL GO WITH A LOWER CHANCE BUT KEEPING CONFIDENCE RESERVED. A FEW INSTANCES OF HEAVY RAIN MAY EXIST AFTER 06Z TONIGHT BUT THE SEVERE THREAT...IF ANY SHOULD BE OVER. QUITE A COOLER AIR MASS EXISTS BEHIND THIS FRONT WITH HIGHS IN THE UPPER 70S EXPECTED ON THURSDAY...NEARLY 10 DEGREES BELOW NORMAL. SO AN UNUSUALLY OVERALL COOL JULY CONTINUES. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 342 AM EDT WED JUL 23 2014 THE MODELS ARE IN A BIT BETTER AGREEMENT TONIGHT WITH RESPECT TO THE PATTERN ALOFT THROUGH THE EXTENDED. THEY ALL DEPICT A STRONG RIDGE OVER THE SOUTHWEST PART OF THE NATION AND A DEEP TROUGH OVER THE NORTHEAST PART OF THE CONTINENT. THIS EASTERN TROUGH EXTENDS SOUTH THROUGH THE APPALACHIANS TO THE GULF COAST KEEPING EAST KENTUCKY IN A PROLONGED PERIOD OF NORTHWEST FLOW. HOWEVER...THE WESTERN RIDGE DOES EXTEND EAST FOR A TIME ON FRIDAY SHIFTING THE SHORTWAVE TRACK TO THE NORTH OF THE STATE AS HEIGHTS RISE LOCALLY. THIS RIDGE QUICKLY RETREATS...THOUGH...SO THAT BY SATURDAY MORNING THE NORTHWEST FLOW...AND ITS PERIODIC WAVES OF ENERGY...WILL AGAIN ENGULF EAST KENTUCKY. THIS IS WHERE THE MODELS CONTINUE TO DISPLAY THE DIFFERENCES THEY HAVE EXHIBITED FOR THE PAST 24 TO 48 HOURS. THE PROBLEMS CENTER ON THE HANDLING OF THE WESTERN PART OF THE DEEP NORTHEAST TROUGH AS IT SHIFTS SOUTHEAST AND INTO THE STATES. THE 00Z GFS AND GEM CONTINUE TO BE QUICKER THAN THE 12Z ECMWF WITH THIS DEVELOPMENT....BUT THE LATEST 00Z ECMWF HAS NARROWED THIS GAP. THIS CONTINUES THE UNCERTAINTY ABOUT THE EXACT EVOLUTION PROCESS OF THE TROUGH/S RENEWED SHIFT INTO THE GREAT LAKES AND OHIO VALLEY. HOWEVER...THE END POINT IS FAIRLY CLEAR BY MONDAY MORNING AS ALL MODELS ARE ON BOARD WITH AN UNSEASONABLY VERY DEEP AND LARGE TROUGH PIVOTING THROUGH THE REGION. THE CORE OF THIS TROUGH DESCENDS WELL SOUTH INTO THE GREAT LAKES AND OHIO VALLEY IN ALL THE MODELS... THOUGH THE GFS ENDS UP BETWEEN 5 AND 10 DECAMETERS LOWER OVER THE CWA BY TUESDAY EVENING OWING TO ITS MORE SOUTHERN CENTERING OF THE TROUGH. THIS GYRE THEN STAYS BASICALLY PARKED OVER THE AREA WITH ABNORMALLY LOW SUMMERTIME HEIGHTS THROUGH THE END OF THE EXTENDED. GIVEN THE UNCERTAINTY WITH THE MID PART OF THE EXTENDED WILL NOT DEVIATE FAR FROM A GENERAL MODEL BLEND AND CONTINUITY FOR THE FORECAST. SENSIBLE WEATHER WILL FEATURE A FAIRLY ACTIVE EXTENDED PERIOD WITH TIMES OF STORMS...A THREAT OF HEAVY RAIN...AND MUCH COOLER TEMPERATURES BY THE START OF NEXT WEEK. FOR THURSDAY NIGHT...SHOWERS AND STORMS WILL CLEAR OUT TO THE EAST WITH A DEPARTING COLD FRONT IN TIME FOR THE START OF THE EXTENDED. THIS WILL BE FOLLOWED BY 24 TO 36 HOURS OF DRY AND COOLER WEATHER BEFORE THE FRONT SURGES BACK NORTH WITH PERIOD OF CONVECTION ANTICIPATED...NOT NECESSARILY CONFORMING TO THE DIURNAL CYCLE SHOULD MCS ACTIVITY SET UP JUST NORTHWEST OF THE CWA. WITH THIS...LOCALLY HEAVY RAIN WILL BE A CONCERN SHOULD ANY ORGANIZED THUNDERSTORMS AFFECT THE SAME AREAS ON CONSECUTIVE DAYS. AFTER A WEEKEND OF STORMY WEATHER BENEATH A QUASI STATIONARY FRONTAL BOUNDARY AND AMPLE HEAT/HUMIDITY...A COLD FRONT WILL LOOK TO SETTLE THINGS DOWN BY MONDAY EVENING AS IT DRIVES SOUTH THROUGH THE AREA IN RESPONSE TO A FAIRLY DEEP SFC LOW MOVING THROUGH THE EASTERN GREAT LAKES. COOLER WX ACCOMPANIES AND FOLLOWS THIS FRONT WITH TUESDAY...POSSIBLY ENDING UP SIMILAR TO THE RECORD SETTING COOLDOWN OF LAST WEEK...ESPECIALLY IF THE SKIES CLEAR QUICK ENOUGH DURING MONDAY NIGHT AND STAY THAT WAY FOR TUESDAY NIGHT. THE CR GRID LOAD PROVIDED A GOOD START TO THE FORECAST FOR THE EXTENDED...THOUGH THE INGEST OF THE 12Z ECMWF HAS LIKELY HURT THE CONSENSUS BLEND. ACCORDINGLY...DID ADJUST THE POPS TO HONE IN ON THE PRIME CHANCES FOR CONVECTION OVER THE WEEKEND AND INTO MONDAY WITH SPECIAL ATTENTION GIVEN TO THE ECMWF AND GFS SOLUTIONS. ALSO... ADJUSTED THE LOW TEMPERATURE GRIDS A TAD TO REFLECT RIDGE AND VALLEY DIFFERENCES THURSDAY AND FRIDAY NIGHT. FINALLY...WENT A BIT LOWER ON MAXES AND MINS FROM MONDAY NIGHT THROUGH TUESDAY...FIGURING THE MODELS ARE PLAYING CATCHUP ON THE UPCOMING UNSEASONABLE WX. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING) ISSUED AT 730 AM EDT WED JUL 23 2014 LOCALIZED MVFR AND IFR VISIBILITIES IN FOG EXISTED EARLY THIS MORNING...INCLUDING AT SME. VISIBILITIES WILL IMPROVE QUICKLY THROUGH 14Z WITH VFR CONDITIONS PREVAILING INTO THE AFTERNOON. A COLD FRONT APPROACHING FROM THE NORTHWEST WILL RESULT IN INCREASING CLOUDS AND THEN NUMEROUS SHOWERS AND THUNDERSTORMS THIS AFTERNOON. COVERAGE OF SHOWERS AND THUNDERSTORMS SHOULD INCREASE CONSIDERABLY AFTER 20Z...WITH MAINLY ISOLATED TO SCATTERED STORMS IN THE LATE MORNING AND EARLY AFTERNOON. THE COLD FRONT WILL MOVE SOUTH OF THE AREA BETWEEN 06Z AND 12Z ON THURSDAY. HOWEVER...AFTER THUNDERSTORMS AND RAIN MOVE OUT OF THE AREA TONIGHT...LOW CLOUD AND FOG IS EXPECTED TO RESULT IN IFR TO MVFR CONDITIONS INTO EARLY THURSDAY MORNING. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SHALLENBERGER LONG TERM...GREIF AVIATION...SBH

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