483 FXUS63 KJKL 101409 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1009 AM EDT WED JUL 10 2013 .UPDATE... ISSUED AT 1000 AM EDT WED JUL 10 2013 UPDATED THE FORECAST TO BETTER REFLECT CURRENT CONDITIONS AND MODEL TRENDS. THE SATELLITE AND RADAR ARE INDICATING A LINE OF SHOWERS MOVING ACROSS THE AREA. THIS AREA SHOULD CONTINUE MOVING ACROSS THE AREA TO THE SOUTHEAST OVER TH NEXT COUPLE OF HOURS. THERE IS AN MCS OUT AHEAD OF THE COLD FRONT WITH ITS SIGHTS SET ON EASTERN KENTUCKY. THE SEVERE POTENTIAL IS A BIT INTERESTING TODAY DUE TO THE AMOUNT OF CLOUD COVER. IN GENERAL...THE SEVERE THREAT WILL NOT BE UNIFORM ACROSS THE AREA TODAY. THE THREAT WILL BE HIGHEST IN AREAS THAT SEE SOME CLEARING AND GOOD HEATING DURING THE REST OF THE MORNING AND EARLY AFTERNOON. THOSE AREAS MAY HAVE ENOUGH INSTABILITY TO GET SOME SEVERE ACTIVITY GOING THIS AFTERNOON AND EVENING. ANOTHER CONCERN FOR TODAY IS FOR SOME NUISANCE FLOODING WHICH MIGHT WILL BE POSSIBLE IN AREAS THAT SEE SLOW MOVING OR TRAINING STORMS. THE PRECIPITABLE WATER THIS AFTERNOON IS ABOUT 1.8 INCHES...SO THE POTENTIAL FOR HEAVY RAIN IS A REAL THREAT. A FLASH FLOOD WATCH IS CURRENTLY UNDER CONSIDERATION AND MAY BE NEEDED AND ISSUED BY NOON. UPDATE ISSUED AT 657 AM EDT WED JUL 10 2013 ORIGINALLY HAD SCT POPS TAPERING OFF TO ISOLATED OVER THE LAST HOUR WHEN MORNING FORECAST PACKAGE WAS SENT OUT. THOUGH SHRA SEEM TO BE WEAKENING...WENT AHEAD AND UPDATED FOR THE NEXT HOUR WITH SCT POPS INSTEAD OF ISOLATED BASED ON CURRENT RADAR TRENDS. SHOWERS SHOULD CONTINUE TO WEAKEN AND TAPER OFF TO MORE ISOLATED COVERAGE OVER THE NEXT COUPLE HOURS. && .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 404 AM EDT WED JUL 10 2013 AN UPPER LEVEL TROUGH JUST NORTH OF THE UPPER GREAT LAKES WILL CONTINUE TO MOVE EASTWARD TODAY...DRAGGING A SURFACE COLD FRONT FROM NW TO SE ACROSS KY OVERNIGHT TONIGHT INTO THE DAY THURSDAY. DRY AIR WILL FILTER IN BEHIND THE FRONTAL PASSAGE AS UPPER LEVEL RIDGING TAKES HOLD OF MUCH OF THE CONUS...WITH SE KY FINALLY DRYING OUT BY THE LATE AFTERNOON/EVENING THURSDAY. TEMPERATURES TODAY WILL BE SOME OF THE HOTTEST AND MOST HUMID WE/VE SEEN IN A WHILE AS WE AWAIT THE COLD FRONTAL PASSAGE. HEAT INDEXES ACROSS THE NORTHERN COUNTIES COULD REACH THE MID TO UPPER 90S...WITH MUCH OF THE REST OF THE CWA IN THE LOW TO MID 90S. NOT MUCH HAS CHANGED ON THE OVERALL FORECAST IDEA. MOIST AND UNSTABLE ATMOSPHERE IS ALREADY IN PLAY ACROSS MUCH OF THE SE AHEAD OF THIS APPROACHING FRONT. THIS HAS PRODUCED AN MCS TO OUR NE...WITH SCATTERED SHOWERS TRAVERSING MUCH OF THE CWA OVERNIGHT. WHILE THESE SHOWERS ARE LIGHT AND WILL HAVE LITTLE IMPACT ON THE REGION...FOCUS THEN TURNS TO THE TODAY/S EXPECTED DAYTIME CONVECTION AHEAD OF THE SURFACE FRONT. HI-RES MODELS ARE STILL IN GOOD AGREEMENT THAT CONVECTION WILL BEGIN BY LATE MORNING/EARLY AFTERNOON TODAY. HOWEVER...THIS IS ABOUT ALL THEY AGREE ON. AS A RESULT...ONLY FELT CONFIDENT ENOUGH TO GO WITH 30 TO 50 POPS THROUGH THE EARLY AFTERNOON...AS WHAT CONVECTION THAT DOES DEVELOP WILL LIKELY BE SCT IN NATURE ACROSS MUCH OF THE CWA. LATEST NAM12 FORECAST SOUNDINGS CONTINUE TO SHOW A WATER LOADED SOUNDING WITH TSRA DEVELOPMENT /CAP BREAKING/ BY 15Z THIS MORNING. INSTABILITY WILL CONTINUE TO INCREASE THROUGHOUT THE AFTERNOON WITH POPS BECOMING NUMEROUS ACROSS THE ENTIRE CWA. THERE IS GOOD POTENTIAL FOR SOME STORMS TO BECOME SEVERE...ESPECIALLY ACROSS THE NORTHERN HALF WHERE SOUNDINGS SHOW A POCKET OF MID LEVEL DRYING CONDUCIVE OF PRODUCING HAIL AND HIGH WINDS. REGARDLESS...ANY SHRA/TSRA THAT DOES DEVELOP WILL BE CAPABLE OF DUMPING A LARGE AMOUNT OF RAIN...SO WILL NEED TO CONTINUE TO BE ON GUARD AGAINST POSSIBLE FLOODING ISSUES ACROSS THE CWA. BY OVERNIGHT TONIGHT...SOME LINGERING TSRA WILL STILL BE POSSIBLE...BUT EXPECT THEM TO DIE DOWN AS STRONG LLVL INVERSION FORMS AND INSTABILITY DUE TO DAYTIME HEATING IS LOST. SHOWERS WILL CONTINUE THROUGHOUT THE NIGHT WITH A LARGE AMOUNT OF MOISTURE STILL IN PLACE ACROSS THE REGION. DRY AIR ALOFT AND IN THE MID LEVELS WILL START WORKING IN ACROSS THE NW BY LATE NIGHT AS FRONT BEGINS PUSHING THROUGH...REACHING THE SURFACE AND CUTTING OFF ANY LINGERING PRECIP CHANCES BY THURS MORNING. THE REST OF THE REGION WILL FOLLOW SUIT THROUGHOUT THE DAY THURS...WITH THE FAR SE COUNTIES DRYING OUT LAST. AS A RESULT...COULD SEE A FEW RUMBLES OF THUNDER IN THE SE DURING THE DAY AS WELL SINCE DAYTIME HEATING WILL ONCE AGAIN HAVE A CHANCE TO WORK WITH THE MOIST ENVIRONMENT AHEAD OF THE FRONT. HIGH PRESSURE AND DRY CONDITIONS WILL FINALLY TAKE HOLD OF THE CWA BY THURSDAY NIGHT BRINGING A MUCH NEEDED BREAK IN PRECIP AND HOT HUMID TEMPERATURES ACROSS MUCH OF KY FOR THE NEXT SEVERAL DAYS. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 447 AM EDT WED JUL 10 2013 THERE IS GOOD AGREEMENT BETWEEN THE GFS AND ECMWF IN THEIR 00Z RUNS...BUT SOME RUN TO RUN CHANGE TAKING PLACE CONCERNING DETAILS AT LONGER RANGE. THIS SUPPORTS GOOD CONFIDENCE EARLY ON...WITH A GRADUAL DECLINE WITH TIME. THE PERIOD SHOULD START WITH SURFACE HIGH PRESSURE OVER THE GREAT LAKES AND AN EASTERN CONUS UPPER TROUGH. THE SURFACE COLD FRONT ASSOCIATED WITH THE TROUGH WILL BE SLOWLY MOVING AWAY AND WEAKENING SOUTHEAST OF THE APPALACHIANS. DRIER AIR WILL BE MOVING INTO OUR LOCAL AREA OUT OF THE HIGH TO OUR NORTH. IT SHOULD PROVIDE MAINLY DRY WEATHER AT LEAST THROUGH SATURDAY NIGHT. THE DRIER AIR MASS WILL HAVE TROUBLE ADVANCING EAST OF THE APPALACHIANS. THE EASTERN CONUS UPPER TROUGH WILL WEAKEN...AND THE GREAT LAKES HIGH WILL ALSO WEAKEN AND SURRENDER ITS INFLUENCE TO A SUBTROPICAL HIGH OVER THE ATLANTIC DURING THE WEEKEND AND EARLY NEXT WEEK. WITH MORE HUMID AIR NEVER TOO FAR AWAY TO OUR SOUTHEAST...IT WILL MAKE A PUSH BACK TO THE NORTHWEST AS THE SUBTROPICAL HIGH BECOMES MORE DOMINANT. THE REMNANTS OF THE UPPER TROUGH IN SOME FORM WILL PERSIST. EXACTLY HOW THE DETAILS OF THIS WEAKNESS IN AN OTHERWISE BUILDING UPPER RIDGE PLAY OUT WITH TIME IS STILL IN QUESTION...WITH GOOD DAY TO DAY TEMPORAL CONSISTENCY IN THE MODELS STILL LACKING. AS LOW LEVEL MOISTURE RETURNS UNDER THE REMAINS OF THE UPPER TROUGH...HAVE USED SLIGHT CHANCE POPS BEGINNING ON SUNDAY...WITH SOME CHANCE POPS INTRODUCED FOR TUESDAY. THE FAVORED TIME FOR PRECIP WILL SHOW AN AFTERNOON/EARLY EVENING DIURNAL TREND. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING) ISSUED AT 701 AM EDT WED JUL 10 2013 SCT SHOWERS HAVE DEVELOPED ACROSS MUCH OF THE OHIO VALLEY OVERNIGHT AND CONTINUE TO MOVE SE ACROSS THE CWA. SHOWERS ARE QUITE LIGHT AND SHOULD NOT HAVE MUCH IN THE WAY OF IMPACTS ON THE TAF SITES. INCLUDED VCSH OVER THE NEXT FEW HOURS AS DIMINISHING NATURE MAKES IT SOMEWHAT UNCERTAIN AS TO WHETHER OR NOT THE TAF SITES WILL BE IMPACTED DIRECTLY. AS WE GO INTO THE DAYTIME HOURS...SCT TSRA WILL BEGIN TO DEVELOP ACROSS MUCH OF THE REGION IN RESPONSE TO AN APPROACHING FRONTAL SYSTEM. WENT WITH PREVIOUS FORECASTS MENTION OF VCTS INSTEAD OF PREDOMINATE TSRA SINCE IT IS STILL UNCERTAIN IF SCT CONVECTION WILL DIRECTLY IMPACT TAF SITES...AND IF SO WHEN AND HOW MUCH IMPACT WILL IT HAVE. AS THE FRONT CONTINUES TO NEAR LATER THIS AFTERNOON AND INTO THE OVERNIGHT...SHOWERS AND THUNDERSTORMS WILL BECOME MORE WIDESPREAD WITH BETTER CONFIDENCE OF IMPACTS BEING FELT AT ALL TAF SITES. FORECAST SOUNDINGS CONTINUE TO SUPPORT THE POTENTIAL FOR HEAVY DOWNPOURS WITH ANY OF THESE SHOWERS AND THUNDERSTORMS TODAY AND TONIGHT...SO COULD SEE VSBY LOWER SUBSTANTIALLY FOR A PERIOD OF TIME IF SHRA/TSRA PASSES OVERHEAD. UPDATES WILL NEED TO BE MADE AS WE NEAR THIS AFTERNOON AND SHRA/TSRA BEGIN TO DEVELOP...SINCE EXACT IMPACTS OF VSBY AND CIGS ARE NOT YET KNOWN AT THIS TIME. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJ SHORT TERM...JMW LONG TERM...HAL AVIATION...JMW