Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 221145 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 745 AM EDT TUE APR 22 2014 .UPDATE...
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ISSUED AT 730 AM EDT TUE APR 22 2014 STILL WAITING ON THE THUNDER...IT DOES APPEAR THAT THE MAIN LINE OF RAIN IS CROSSING EAST KENTUCKY CURRENTLY...IN LINE WITH THE LATEST HRRR. HAVE HIGHLIGHTED THIS WITH THE HIGHEST POPS AND BEST CHANCE FOR THUNDER FOLLOWED BY LOWER POPS INTO THE EARLY AFTERNOON. ALSO FINE TUNED THE T AND TD GRIDS THROUGH MID MORNING BASED ON THE CURRENT OBS AND TRENDS. THESE GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS.
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&& .SHORT TERM...(TODAY THROUGH WEDNESDAY) ISSUED AT 340 AM EDT TUE APR 22 2014 06Z SFC ANALYSIS SHOWS A WEAK COLD FRONT APPROACHING KENTUCKY FROM A PARENT LOW CROSSING THE EASTERN GREAT LAKES. SCATTERED LIGHT SHOWERS ARE MOVING THROUGH EAST KENTUCKY EARLY THIS MORNING IN ADVANCE OF THIS FRONT BENEATH HIGH AND MID LEVEL CLOUDS. SO FAR...ACTUAL MEASUREMENT BY THE SHOWERS HAS BEEN HARD TO COME BY...BUT A FEW PROMISING CLUSTERS ARE DEVELOPING NORTH OF INTERSTATE CORRIDOR ON RADAR. DESPITE THE THREAT OF SHOWERS AND THE PERSISTENT CLOUD COVER...TEMPERATURES THROUGH THE AREA HAVE BEEN ABLE TO ESTABLISH A SMALL RIDGE TO VALLEY DIFFERENCE AS THE EASTERN VALLEYS ARE SITTING IN THE MID 50S WHILE LOW TO MID 60S ARE FOUND ON THE RIDGES. THIS SHOULD EVEN OUT AS THE AIR SATURATES LATER THIS NIGHT WITH A GRADUAL UPTICK IN SHOWER COVERAGE. DEWPOINTS HAVE COME UP INTO THE LOWER 50S FOR MOST OF THE AREA...THOUGH SOME 40S ARE FOUND ON THE RIDGES AND IN THE FAR EAST. MEANWHILE...WINDS ARE LIGHT AND GENERALLY FROM THE SOUTHWEST THROUGH THE AREA. THE MODELS ARE IN GOOD AGREEMENT ALOFT AS THEY ALL DEPICT A DEVELOPING TROUGH SWEEPING THROUGH THE NORTHEAST OHIO VALLEY LATER TODAY PROMPTING HEIGHT FALLS ACROSS EAST KENTUCKY. THE BEST ENERGY WITH THIS TROUGH STAYS WELL TO THE NORTH AND EAST OF KENTUCKY...WITH SOME WEAKER AMOUNTS PASSING THROUGH THIS MORNING. THE NORTHEAST TROUGH DOES EXIT THE REGION LATER WEDNESDAY ALLOWING HEIGHTS TO BUILD BACK OVER KENTUCKY AMIDST RIDGING INBOUND FROM THE SOUTHERN PLAINS. WITH THE AGREEMENT ALOFT...HAVE FAVORED A GENERAL MODEL BLEND FOR THE SHORT TERM PORTION OF THE FORECAST. HOWEVER...FOR WEATHER DETAILS HAVE LEANED MORE HEAVILY ON THE HIGHER RESOLUTION HRRR AND NAM12 THROUGH 00Z WEDNESDAY. SENSIBLE WEATHER WILL FEATURE A DAMP AND COOLER DAY AS THE FRONT GRADUALLY MAKES ITS WAY THROUGH EAST KENTUCKY. THE BEST CHANCE FOR SOME RAIN OF NOTE WILL BE RIGHT WITH THE BOUNDARY/S PASSAGE LATER THIS MORNING. THE THERMAL PROFILE STILL LOOKS UNSTABLE ENOUGH TO ALLOW FOR A THUNDERSTORM THROUGH NOON ACROSS THE AREA SO WILL KEEP THAT IN THE FORECAST. EVEN SO...THE LACK OF ANY ORGANIZATION WILL KEEP ANY STORMS THAT OCCUR TO A MORE GARDEN VARIETY LEVEL AND ALSO PREVENT MUCH IN THE WAY OF SOAKING RAINS FOR ALL BUT A FEW SPOTS. DRIER AND COOLER AIR MOVES INTO THE CWA LATER THIS AFTERNOON IN THE WAKE OF THE FRONT ENDING THE SHOWER THREAT AND EVENTUALLY CLEARING THE CLOUDS. THE DECENT CAA BEHIND THE BOUNDARY TONIGHT WILL COMPOUND RADIATIONAL COOLING IN THE MORE SHELTERED VALLEYS TO SEND TEMPERATURES THERE INTO THE MIDDLE 30S. THIS...COMBINED WITH LIGHT WINDS...WILL LEAVE THEM VULNERABLE TO PATCHY FROST BY DAWN. HAVE ADDED THIS TO THE WX GRIDS AND WILL CONTINUE ITS MENTION IN THE HWO. FOR WEDNESDAY...AFTER A CHILLY START...READINGS WILL CLIMB INTO THE MID 60S MOST PLACES... THOUGH THE ARRIVAL OF MID LEVEL CLOUDS LATE IN THE DAY WILL DO LITTLE TO HELP TEMPS RISE IN THE AFTERNOON. STARTED OUT WITH THE BC/CONSSHORT GUIDANCE FOR THE TEMPS... DEWPOINTS...AND WIND GRIDS FOR THE FIRST 24 HOURS OF THE FORECAST FOLLOWED BY THE BC/CONSALL THEREAFTER. THE DEWPOINTS WERE ADJUSTED LOWER FOR MIDDAY AND EARLY AFTERNOON ON WEDNESDAY FOR EXTRA DRY AIR MIXDOWN. DID MAKE SOME FINE TUNE ADJUSTMENTS TO THE CONSALL FOR LOWS TONIGHT AND HIGHS ON WEDNESDAY. AS FOR POPS...ENDED UP SIMILAR TO THE MOS GUIDANCE TODAY AND ALSO WITH ITS LOW SINGLE DIGIT VALUES TONIGHT AND WEDNESDAY. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 330 AM EDT TUE APR 22 2014 THE MODELS WERE IN DECENT AGREEMENT IN THE EXTENDED THIS TIME AROUND. THE MODEL CONSENSUS IS FOR LARGE TROUGH OF LOW PRESSURE TO MOVE EASTWARD OFF THE PACIFIC OCEAN AND ACROSS THE CONUS WEDNESDAY NIGHT THROUGH FRIDAY NIGHT. THE MODELS DISPLAYED SOME SMALL DIFFERENCES IN THE STRENGTH OF THIS SYSTEM AND ITS EXACT TIMING...BUT OVERALL AGREEMENT WAS SOLID. THE SURFACE REFLECTION OF THE UPPER TROUGH AND ITS ASSOCIATED AREA OF LOW PRESSURE WILL BE AN AREA OF LOW PRESSURE THAT IS FAIRLY INTENSE FOR THIS TIME OF YEAR...ALONG WITH A TRAILING COLD FRONT. BASED ON THE LATEST MODEL DATA...IT APPEARS THAT THE FRONT ITSELF WILL NOT BE ALL THAT IMPRESSIVE IN AND OFF ITSELF. HOWEVER...THE BOUNDARY SHOULD BE WELL DEFINED ENOUGH...AND HAVE ENOUGH GULF MOISTURE TO TAP INTO...TO PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS AS IT MOVES ACROSS THE REGION THURSDAY NIGHT INTO EARLY FRIDAY MORNING. WITH A VIGOROUS UPPER TROUGH STEERING IT...THE SURFACE SYSTEM SHOULD MOVE ACROSS THE AREA FAIRLY QUICKLY. THAT BEING SAID...ADJUSTED THE FORECAST GRIDS TO REFLECT ABOUT A 20 HOUR PERIOD OF PRECIPITATION BEGINNING LATE THURSDAY AFTERNOON AND LASTING INTO LATE FRIDAY MORNING. THE LATEST MODEL DATA SUGGESTS MODEST INSTABILITY AT BEST DURING FRONTAL PASSAGE...SO THUNDER SHOULD BE FAIRLY ISOLATED. TEMPERATURES IN OUR DEEPEST VALLEYS COULD DROP ENOUGH TO ALLOW FOR SOME FROST FORMATION AROUND THE AREA. BASED ON HOW WARM IT HAS BEEN LATELY...AND HOW WARM IT WILL BE LEADING INTO WEDNESDAY NIGHT...WILL CONTINUE WITH MENTION OF PATCHY VALLEY FROST IN THE GRIDS FOR EARLY THURSDAY MORNING. A SECOND WEATHER IS PROGGED TO AFFECT THE AREA OVER THE WEEKEND AND INTO THE BEGINNING OF THE UPCOMING WORK WEEK. THE ISSUE WITH THIS SYSTEM LIES IN THE AMOUNT OF UNCERTAINTY BETWEEN THE MODELS AS TO THE TIMING AND INTENSITY OF THIS WEATHER SYSTEM. AS IT STANDS...THE GFS MODEL IS PRODUCING STRONG AND MORE SLOWLY EVOLVING AREA OF LOW PRESSURE THAN THE ECMWF. BASED ON THE LATEST RUN OF THE ECMWF...EASTERN KENTUCKY COULD EXPERIENCE ISOLATED INSTANCES OF PRECIPITATION BEGINNING AS EARLY AS SATURDAY AFTERNOON AND LASTING THROUGH THE END OF THE PERIOD ON MONDAY. THE GFS...ON THE OTHER HAND...HOLDS OFF ON INTRODUCING PRECIPITATION TO THE AREA UNTIL LATE SATURDAY NIGHT. THE SOLUTION FOR THIS PORTION OF THE FORECAST WAS TO GO WITH A BLEND OF THE TWO MODELS...GFS AND ECWMF...TO TRY AND ACCOUNT FOR THE AMOUNT OF DIFFERENCE BETWEEN THEM. THAT BEING SAID...THE FORECAST SOLUTION FOR LATE SATURDAY ONWARD IS OF LOW CONFIDENCE...WITH A SLIGHT BIAS TOWARD THE NORMALLY MORE RELIABLE ECMWF SOLUTION. THAT BEING SAID...WENT WITH A SLIGHT CHANCE OF SHOWERS AND STORMS BEGINNING SATURDAY AFTERNOON IN ASSOCIATION WITH A SLOW MOVING WARM FRONTAL BOUNDARY. THE REST OF THE WEEKEND AND FIRST COUPLE OF DAYS OF THE WORK WEEK WILL FEATURE A MEANDERING SURFACE FRONTAL BOUNDARY WITH SCATTERED SHOWERS AND STORMS FIRING ALONG IT FROM TIME TO TIME. WITH INSTABILITY ONCE AGAIN LIMITED...DECIDED TO GO WITH MENTION OF ISOLATED THUNDER ACROSS THE AREA. TEMPERATURES THROUGHOUT THE PERIOD...WITH THE POSSIBLE EXCEPTION OF THURSDAY MORNINGS LOWS...SHOULD BE AT OR SLIGHTLY ABOVE NORMAL FOR THIS TIME OF YEAR. THE WARMEST DAYS WILL LIKELY BE THURSDAY THROUGH SATURDAY...AS THE GULF OPENS UP AS WE BECOME FIRMLY ENTRENCHED IN THE WARM SECTOR OF A PASSING CYCLONE. HIGHS IN THE LOW TO MID 70S WILL BE COMMON ON THESE DAYS. ONCE THE SECOND AREA OF LOW PRESSURE BEGINS TO INFLUENCE THE REGION AND THE SURFACE FRONTS STALLS OUT ACROSS THE AREA...TEMPERATURES WILL BE QUITE A BIT A COOLER DUE TO THE INFLUENCE OF CLOUDS AND PRECIPITATION. HIGHS FROM SUNDAY ONWARD WILL AVERAGE MOSTLY IN THE 60S AND SHOULD HOVER AROUND NORMAL VALUES EACH DAY. && .AVIATION...
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(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING) ISSUED AT 745 AM EDT TUE APR 22 2014 VFR CONDITIONS WILL SPLIT TIME WITH SOME MVFR CIGS AND VIS OVER THE NEXT FEW HOURS AS THE MAIN LINE OF SHOWERS MOVES THROUGH. HAVE YANKED THE THUNDER CHANCES AS THE SHOWERS ARE NOT SHOWING MUCH SIGNS OF BEING TOO ROBUST...SO FAR. TO COVER LINGERING SHOWERS THROUGH THE FIRST PART OF THE AFTERNOON AND WHEN THE ACTUAL COLD FRONT GOES THROUGH HAVE INCLUDED A VCSH MENTION IN THE TAFS. DRY AIR WILL THEN FILTER IN LATER THIS AFTERNOON...WITH ISOLATED SHOWERS COMING TO AN END AND CIGS RISING TO VFR AGAIN BEFORE DISSIPATING. WEST TO NORTHWEST WINDS WILL PICK UP AT 10 TO 15 KTS FROM THE WEST THIS MORNING...BECOMING MORE NORTH WITH TIME.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GREIF LONG TERM...AR AVIATION...GREIF

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