Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 070557 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 157 AM EDT TUE JUL 7 2015 .UPDATE... ISSUED AT 1220 AM EDT TUE JUL 7 2015 QUICK UPDATE TO FRESHEN UP THE GRIDS AND ALIGN T/TD GRIDS WITH RECENT OBS. OTHERWISE FORECAST REMAINS ON TRACK FOR TONIGHT. UPDATE ISSUED AT 935 PM EDT MON JUL 6 2015 A NEW SET OF ZONES WAS JUST SENT OUT. THE FORECAST GRIDS AND FORECAST UPDATE WITH BOTH REFLECT THE REMOVAL OF PRECIPITATION FROM THE OVERNIGHT PERIOD. THE LATEST MODEL DATA STILL DOES NOT SUPPORT PRECIP FORMING OVERNIGHT AND THERE IS NOTHING DEVELOPING ANYWHERE DOWNSTREAM THAT WOULD MAKE IT INTO EASTERN KENTUCKY OVERNIGHT EITHER. ANY STALE WORDING IN THE PREVIOUS FORECAST TEXT PRODUCE WAS ALSO REMOVED. A NEW HAZARDOUS WEATHER OUTLOOK WILL ALSO BE ISSUED MOMENTARILY THAT MENTIONS ONLY PATCHY DENSE FOG FOR LATER TONIGHT AND TO CORRECT A TYPO. UPDATE ISSUED AT 755 PM EDT MON JUL 6 2015 JUST FINISHED INGESTING THE LATEST OBS DATA INTO THE FORECAST GRIDS TO ESTABLISH NEW TRENDS. NO MAJOR CHANGES TO THE FORECAST REQUIRED AT THIS TIME. TOWARD THE END OF THE SHIFT WILL BE CONSIDERING REMOVING PRECIPITATION FROM THE TONIGHT PERIOD OF THE FORECAST...AS THE LATEST SHORT TERM MODELS SIMPLY DO NOT SUPPORT IT DUE TO LACK OF ANY TRIGGERING MECHANISM. && .SHORT TERM...(THIS EVENING THROUGH TUESDAY NIGHT) ISSUED AT 350 PM EDT MON JUL 6 2015 THE MID AND UPPER LEVEL LOW PRESSURE SYSTEM CONTINUES TO DEPART TO THE NORTHEAST OF THE REGION THIS AFTERNOON. A WEAK MID LEVEL RIDGE IS BUILDING TOWARD THE REGION IN BETWEEN THIS DEPARTING SYSTEM AND A TROUGH MOVING ACROSS THE PLAINS STATES AND APPROACHING THE GREAT LAKES AND MS VALLEY. THERE HAVE BEEN A FEW SHOWERS ON THE OUTER EDGE OF THE DEPARTING LOW...AND OVER THE CUMBERLAND PLATEAU...BUT OVERALL MUCH LESS COVERAGE COMPARED TO 24 HOURS AGO. A MID LEVEL RIDGE WILL BRIEFLY WORK EAST ACROSS THE COMMONWEALTH THIS EVENING INTO THE OVERNIGHT...WITH THE AXIS OF THIS RIDGE MOVING EAST BY DAWN. THIS WILL ALLOW FOR THE NEXT SHORTWAVE TO BEGIN TO APPROACH THE REGION WITH THE CORRESPONDING COLD FRONT ALSO ENTERING THE OH VALLEY REGION. THIS SYSTEM SHOULD BE A FOCUS FOR CONVECTION MAINLY FROM TUE AFTERNOON INTO TUE EVENING AS DAYTIME HEATING AND A MOIST AIRMASS WILL BE IN PLACE ALONG AND AHEAD OF THE BOUNDARY. THE BEST DYNAMICS AND SHEAR HOWEVER SHOULD RESIDE GENERALLY NORTH OF THE REGION...BUT WEAK SHORTWAVES IN SW FLOW ALOFT WILL BRING A THREAT FOR CONVECTION THROUGH THE END OF THE PERIOD. COVERAGE OF CONVECTION SHOULD BE GREATEST ON TUE AFTERNOON AND TUE EVENING. THE BEST COMBINATION OF THE SHEAR AND INSTABILITY SHOULD BE ACROSS THE NW PART OF THE CWA...OR IN THE SPC MARGINAL CONVECTIVE RISK FOR DAY 2. A COUPLE OF STORMS COULD PRODUCE STRONG WINDS GUSTS. HOWEVER...GIVEN THE RECENT WET PERIOD...THE POTENTIAL FOR THE FRONT TO STALL OR SLOW DOWN AND GENERALLY BE ALIGNED PARALLEL TO THE UPPER LEVEL FLOW AND STORMS NOT EXPECTED TO MOVE ALL THAT SWIFTLY...FLASH FLOODING COULD AGAIN BECOME A CONCERN BY THE END OF THE PERIOD OR INTO THE LONG TERM PERIOD. PW IS NOT EXPECTED TO BE SUSTAINED INORDINATELY HIGH...BUT THE POTENTIAL FOR TRAINING OR REPEATED ROUNDS APPEARS TO BE THERE. AFTER ANY LINGERING SHOWERS DISSIPATE BY EARLY EVENING...THE DRIEST PART OF THE PERIOD WILL BE TONIGHT. MOST CONVECTION SHOULD HOLD OFF UNTIL THE DAYTIME PERIOD LATE TONIGHT...BUT STRAY CONVECTION CANNOT BE RULED OUT IN THE WARM SECTOR TOWARD DAWN. OUTSIDE OF CONVECTION...VALLEY FOG...DENSE IS EXPECTED WITH THE WET GROUND IN PLACE FORM RECENT RAINFALL. THE HIGHEST POPS WERE USED IN THE NORTH...LIKELY WITH SCATTERED POPS IN THE SOUTH. .LONG TERM...(WEDNESDAY THROUGH MONDAY) ISSUED AT 340 PM EDT MON JUL 6 2015 MODELS ARE IN DECENT AGREEMENT WITH THE OVERALL UPPER LEVEL PATTERN AS WE MOVE INTO THE LONG TERM PORTION OF THE FORECAST. THE TROUGHING ACROSS THE EASTERN CONUS BREAKS DOWN AND LEADS TO FAIRLY ZONAL FLOW ACROSS MUCH OF THE OHIO VALLEY INITIALLY...WHILE TROUGH BUILDS ACROSS THE WESTERN CONUS. THROUGH THE PERIOD SUB TROPICAL RIDGE BUILDS ACROSS THE SOUTHEASTERN CONUS SENDING MEAN FLOW NORTH OF EASTERN KENTUCKY. THEN THIS UPPER LEVEL RIDGE BEGINS TO SHIFT WEST AT THE END OF THE PERIOD AND WE GET BACK INTO A STORMIER NW FLOW. OVERALL SURFACE FEATURES LEAD TO A BIT LESS AGREEMENT FROM THE GUIDANCE SUITES. THIS IS DUE TO THE SURFACE BOUNDARY ACROSS THE OHIO VALLEY AND THE INTERACTION WITH BUILDING UPPER LEVEL RIDGE ACROSS THE SOUTHEASTERN CONUS. MOST MODELS BESIDE THE OPERATIONAL ECMWF KEEP THIS BOUNDARY NORTH OF EASTERN KENTUCKY GENERALLY DRAPED ALONG THE OHIO RIVER REGION...WITH THE OUTLIER ECMWF ALLOWING A BIT MORE SOUTHWARD PROGRESSION. GIVEN THE BUILDING RIDGE THIS MORE SOUTHERN SOLUTION SEEMS TO BE LESS LIKELY BUT WOULD TEND TO LEAN TOWARD A CONSENSUS BLEND APPROACH AT THIS POINT. THIS WOULD LEAD TO BETTER CHANCES OF POPS ACROSS THE NORTHERN PORTIONS OF EASTERN KENTUCKY...WHILE SLIGHT CHANCES WOULD BE POSSIBLE ACROSS THE SOUTHERN HALF OF THE REGION. ONE THING TO KEEP IN MIND IS OVERALL STEERING FLOW BECOMES QUIET WEAK ONCE THE RIDGING BUILDS NORTH. THIS WILL LEAD TO POTENTIAL OF SLOW MOVING STORMS AND LOCALLY HEAVY RAINFALL. THIS IS INDICATED WITH SOME MODEL SOUNDING SUGGESTING PWATS NEAR THE 2.00 INCH MARK AND SLOWER MEAN WINDS. WHILE TOWARD THE END OF THE LONG TERM THIS RIDGE SHIFTS WEST ACROSS THE PLAINS LEADING TO BETTER CHANCES OF STORMS IN THE EAST...WITH INCREASED POTENTIAL FOR SURFACE LOW/FRONTS AND MCS/S MOVING SOUTHEAST INTO THE REGION. GIVEN SUB TROPICAL/THERMAL RIDGE BUILDING ACROSS THE REGION EXPECT OVERALL TEMPERATURES TO CLIMB TO NEAR AND ABOVE NORMAL THROUGH THE PERIOD. THIS IS ALSO BACKED UP BY THE 6 TO 10 DAY FORECAST FROM THE CPC. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 155 AM EDT TUE JUL 7 2015 GENERALLY MVFR CONDITIONS PREVAIL ACROSS TAF SITES CURRENTLY...WITH A DROP TO NEAR IFR OR BELOW AT SME AND LOZ BY 09Z LIKELY. THE REMAINING SITES SHOULD STAY AT MVFR FOR THE REMAINDER OF THE NIGHT BEFORE IMPROVING TO VFR BY 13Z. THE FIRST SHOWERS AND STORMS OF THE DAY WILL LIKELY BEGIN MOVING ACROSS THE AREA AROUND 18Z SO HAVE INCLUDED VCTS AT SYM WHERE THERE ARE HIGHER CHANCES FOR POPS...WITH VCSH ELSEWHERE. ASSUMING THE TAF SITES SEE SOME RAIN TOMORROW...HAVE INTRODUCED BR NEAR THE END OF THE TAF PERIOD ACROSS ALL TAF SITES. WINDS WILL BE LIGHT AND VARIABLE THROUGH MOST OF THE PERIOD WITH HIGHER GUSTS ASSOCIATED WITH ANY THUNDERSTORMS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JVM SHORT TERM...JP LONG TERM...DJ AVIATION...JVM

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