Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 281931 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 331 PM EDT THU AUG 28 2014 .SHORT TERM...
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(THIS EVENING THROUGH FRIDAY NIGHT) ISSUED AT 331 PM EDT THU AUG 28 2014 SURFACE HIGH PRESSURE CURRENTLY REIGNS FROM THE GREAT LAKES INTO THE OHIO VALLEY. BROAD LOW PRESSURE CENTERED ACROSS THE PLAINS HAS A WARM FRONT BRANCHED OUT TO THE ESE...BECOMING MORE STATIONARY AND ILL- DEFINED ACROSS SOUTHERN KENTUCKY. ALOFT...AN UPPER LEVEL RIDGE AXIS REMAINS POISED ACROSS THE MISSISSIPPI VALLEY...WITH AN UPPER LOW/TROUGH CRUISING INTO THE PLAINS. CONVECTION HAS POPPED UP ALONG THE STATIONARY BOUNDARY...MAINLY ACROSS THE SOUTHWESTERN PORTION OF THE COMMONWEALTH...WHERE BETTER INSTABILITY HAS BUILT UP DURING THE AFTERNOON. SO FAR...ONLY A FEW SHOWERS HAVE DOTTED PORTIONS OF THE CUMBERLAND VALLEY WITHIN EASTERN KENTUCKY. THE MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM...WITH THE UPPER LEVEL RIDGE AMPLIFYING AND SHIFTING EAST WITH TIME AS THE UPPER TROUGH DAMPENS AND RIDES NORTHEAST ACROSS THE PLAINS...REACHING NEAR THE GREAT LAKES REGION BY EARLY SATURDAY MORNING. THIS WILL KEEP PLENTY OF HEAT AND HUMIDITY ACROSS EASTERN KENTUCKY INTO THE START OF THE HOLIDAY WEEKEND...WITH THE THREAT OF SOME ISOLATED CONVECTION... MAINLY DURING THE FAVORED AFTERNOON AND EARLY EVENING HOURS. ANY ISOLATED SHOWERS AND A STRAY THUNDERSTORM WILL WIND DOWN QUICKLY THROUGH EARLY THIS EVENING AS WE LOSE INSTABILITY. FOG WILL LIKELY SET IN ONCE AGAIN...ALTHOUGH IT SHOULD BE MORE RESTRICTED TO THE VALLEYS COMPARED TO LAST NIGHT. OVERNIGHT LOWS WILL GENERALLY RANGE FROM THE LOW TO MID 60S. FOR FRIDAY...HIGH TEMPERATURES WILL APPROACH THE 90 DEGREE MARK...WITH ISOLATED CONVECTION THREATENING DURING THE AFTERNOON AND EVENING HOURS. FRIDAY NIGHT WILL FEATURE A MORE BALMY NIGHT...WITH VALLEY FOG AND LOWS IN THE MID TO UPPER 60S FOR MOST. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 331 PM EDT THU AUG 28 2014 THE EXTENDED WILL BEGIN WITH A BROAD BUT WEAKENING RIDGE OF HIGH PRESSURE PARKED OVER THE SOUTHEASTERN CONUS ON SATURDAY. AT THE SAME TIME...THE MODELS HAVE A RATHER POTENT LOW PRESSURE SYSTEM ALOFT APPROACHING FROM THE PLAINS. THE FRONT TRAILING FROM THIS SYSTEM WILL PROVIDE OUR NEXT GOOD CHANCE OF RAIN SATURDAY NIGHT INTO SUNDAY. THE PRIMARY CONCERNS WITH THIS NEXT WEATHER PATTERN WILL BE THE LARGE AMOUNTS OF GULF MOISTURE THAT ARE LIKELY TO STREAM INTO THE TENNESSEE AND OHIO VALLEY REGIONS...AND THE SLOWNESS OF THE FRONT TO EXIT THE AREA. BASED ON THE CURRENT DATA...THE FRONT SHOULD STALL OUT ACROSS THE AREA THROUGH MONDAY NIGHT. A SECOND MUCH LESS WELL DEFINED BOUNDARY WILL THEN AFFECT THE AREA ON THE HEELS OF THE ORIGINAL FRONT FROM THE WEEKEND. THE ISSUE WITH THE SECOND BOUNDARY IS TIMING AND MOISTURE AVAILABILITY...WHICH THE GFS AND ECMWF WERE HANDLING QUITE DIFFERENTLY. IN FACT...DURING THE MIDDLE OF THE WEEK...THE ECMWF STALLS OUT ANOTHER FRONT ACROSS THE AREA...WITH AMPLE MOISTURE INTERACTING WITH THE BOUNDARY. THE GFS...HOWEVER...KEEPS ITS BOUNDARY MOSTLY TO OUR NORTH...ALONG WITH MOST OF THE MOISTURE ASSOCIATED WITH IT. THAT BEING SAID...THE ECMWF SOLUTION WAS USED FOR SYSTEM EVOLUTION AND PRECIPITATION COVERAGE AND AMOUNTS FROM SATURDAY THROUGH MONDAY NIGHT. AFTER THAT...A BLEND OF THE TWO MODELS WAS USED TO CREATE THE NEW FORECAST...WITH LOWER THAN MEXMOS VALUES FOR POPS EACH OF THOSE DAYS AND NIGHTS DO TO THE UNCERTAINTY. THE BEST TIME FRAME FOR RAIN LOOKS TO BE SATURDAY NIGHT THROUGH MONDAY NIGHT DUE TO THE STALLED FRONT. THERE WILL ALSO BE THE POTENTIAL FOR LOCALLY HEAVY RAINFALL TO START THE PERIOD AS THE LATEST FORECAST SOUNDINGS ARE PREDICTING BETWEEN 1.8 TO JUST OVER 2 INCHES OF PRECIPITABLE WATER AND A TALL SKINNY CAPE PROFILE. THIS WILL BEAR WATCHING OVER THE NEXT COUPLE OF DAYS. BASED ON THIS TYPE OF INSTABILITY PROFILE...THE POTENTIAL FOR THUNDERSTORM ACTIVITY SHOULD BE A LITTLE LESS THAN WE HAVE SEEN OVER THE PAST WEEK OR SO. TEMPERATURES THROUGHOUT MOST OF THE PERIOD LOOK TO BE SLIGHTLY WARMER THAN NORMAL DUE TO PERSISTENT SOUTHERLY FLOW ASSOCIATED WITH EACH OF THE PASSING WEATHER SYSTEMS AND THE LARGE AMOUNT OF WARM MOIST AIR THAT WILL BE TRANSPORTED INTO THE AREA OFF THE GULF OF MEXICO. HIGHS EACH DAY WILL AVERAGE IN THE MID TO UPPER 80S...WITH OVERNIGHT LOWS BOTTOMING OUT AROUND 70. THE ONE EXCEPTION TO THIS RULE WOULD BE SUNDAY...WHICH SHOULD SEE COOLER THAN NORMAL TEMPERATURES DUE TO THE EXTENSIVE CLOUD AND LONG LASTING PRECIPITATION THAT IS EXPECTED.
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&& .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON) ISSUED AT 208 PM EDT THU AUG 28 2014 MVFR STRATOCU WILL SCATTER OUT AND LIFT THROUGH 19Z. A FEW SHOWERS AND A STRAY THUNDERSTORM WILL BE SEEN GENERALLY ALONG AND SOUTH OF THE HAL ROGERS PARKWAY AND HIGHWAY 80 CORRIDORS THROUGH EARLY THIS EVENING. GIVEN THE ISOLATED AREAL COVERAGE...DECIDED TO LEAVE OUT ANY CONVECTIVE MENTION AT LOZ AND SME. ANY ACTIVITY WILL DIMINISH QUICKLY BY AROUND 01Z...WITH FOG DEVELOPING ONCE AGAIN BETWEEN 05 AND 10Z. HAVE KEPT THINGS MVFR FOR THE TAF SITES...AS WINDS WILL BE VEERING AROUND TO A LIGHT SOUTHEASTERLY COMPONENT. IFR OR WORSE FOG IS EXPECTED ONCE AGAIN IN THE DEEPER RIVER VALLEYS. THE FOG WILL BE BURNING OFF BY AROUND 13Z FRIDAY...WITH SOME ISOLATED CONVECTION THREATENING ONCE AGAIN BY FRIDAY AFTERNOON. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GEOGERIAN LONG TERM...AR AVIATION...GEOGERIAN

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