Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 250730 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 330 AM EDT FRI JUL 25 2014 .SHORT TERM...
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(TODAY THROUGH SATURDAY) ISSUED AT 330 AM EDT FRI JUL 25 2014 07Z SFC ANALYSIS SHOWS COOL AND DRIER HIGH PRESSURE IN CONTROL OVER THE OHIO VALLEY AND EAST KENTUCKY. THIS HAS CLEARED THE SKY OF THE MID AND LOW LEVEL CLOUDS FROM EARLIER IN THE EVENING. AS A RESULT... WHEN COMBINED WITH THE MOIST BOUNDARY LAYER...FOG FORMED EARLY IN THE NIGHT AND HAS BECOME DENSE OVER MUCH OF THE AREA. AN SPS HAS BEEN ISSUED TO ADDRESS THIS...THOUGH A DENSE FOG ADVISORY APPEARS IN ORDER JUDGING FROM THE LATEST OBS AND WEB CAMS. THIS WILL BE ISSUED WITH THE ZONES AND GRID PACKAGE. OTHERWISE...WINDS ARE LIGHT THROUGH THE AREA WITH TEMPERATURES AND DEWPOINTS ALL WITHIN A COUPLE OF DEGREES OF 60. THE EXCEPTION IS FAR NORTHWEST PARTS OF THE AREA WHERE THERE REMAINS A DEWPOINT SPREAD OWING TO LOWER LEVELS OF MOISTURE. WILL LEAVE THESE PLACES OUT OF THE DENSE FOG ADVISORY...BUT MENTION PATCHY FOG IN THEIR GRIDS AND ZONES. THE MODELS ARE IN GOOD AGREEMENT ALOFT THROUGH THE SHORT TERM WITH A BRIEF RETREAT OF THE EASTERN TROUGH IN THE FACE OF THE STRONG WESTERN RIDGE FLATTENING OUT AND PUSHING HIGHER HEIGHTS EAST INTO KENTUCKY THROUGH MIDDAY SATURDAY. THIS WILL KEEP THE BULK OF ANY SHORTWAVE ACTIVITY NORTHEAST OF THE CWA THROUGH SATURDAY MORNING. HOWEVER...THE RIDGE PULLS BACK LATER SATURDAY UNDER THE INFLUENCE OF A MORE SIGNIFICANT MID LEVEL WAVE THAT WILL CROSS INTO THE WESTERN OHIO VALLEY THAT EVENING. THIS WAVE HAS BEEN A KEY ONE FOR THE PAST SEVERAL RUNS THAT THE MODELS BLOW UP WITH INDICATIONS OF A HEALTHY MCS. SPC HAS PLACED THE NORTHERN PART OF OUR CWA IN A SLIGHT RISK FOR THIS POTENTIAL LATER SATURDAY NIGHT...WITH DAMAGING WINDS THE GREATEST THREAT. GIVEN THE MODEL SIMILARITIES HAVE GONE WITH THE HIGHER RESOLUTION NAM12 MOST CLOSELY. SENSIBLE WEATHER WILL FEATURE A PLEASANT DAY WITH LOW AFTERNOON HUMIDITIES AND MOSTLY SUNNY SKIES...ONCE THE DENSE FOG BURNS OFF THIS MORNING. ALTHOUGH THE STORM TRACK WILL STAY NORTH OF THE AREA THROUGH MIDDAY SATURDAY...THE CLOUDS ASSOCIATED WITH ANY CONVECTIVE DEVELOPMENT WILL LIKELY DRIFT INTO OUR AREA AND KEEP TEMPS FROM BOTTOMING OUT TONIGHT AND LIKELY KEEP FOG CONFINED TO JUST THE VALLEYS. FOR SATURDAY...THE HEAT AND HUMIDITY RETURN TO THE AREA WITH A POTENTIAL FOR STORMS BY EVENING...MAINLY IN THE NORTH... DEPENDING ON THE MCS ACTIVITY TO THE NORTHWEST OUT AHEAD OF THE MAIN DEVELOPMENT ANTICIPATED LATER IN THE NIGHT. AGAIN USED THE CONSSHORT AS A STARTING POINT FOR TEMPERATURES... DEWPOINTS...AND WINDS THROUGH THE FIRST 24 HOURS AND THE CONSALL THEREAFTER. DID FINE TUNE LOWS TONIGHT FOR SOME SMALL RIDGE AND VALLEY DIFFERENCES. AS FOR POPS...WENT A TAD HIGHER THAN THE MOS NUMBERS FOR SATURDAY AFTERNOON...AND JUST SINGLE DIGITS...IN LINE WITH MOS...UNTIL THEN. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 451 PM EDT THU JUL 24 2014 THE MAIN FEATURE DURING THE PERIOD WILL BE A LARGE LONGWAVE TROUGH WHICH AMPLIFIES OVER EASTERN NORTH AMERICA DURING THE FIRST FEW DAYS. LOW LEVEL SOUTHWESTERLY FLOW WILL BRING ADVECTION OF VERY WARM AIR INTO THE REGION ON SATURDAY. SIGNIFICANT MOISTURE OFF THE GULF OF MEXICO WILL LAG BEHIND...BUT WILL EVENTUALLY ARRIVE SATURDAY NIGHT AND SUNDAY TO SUPPORT HIGHER POPS. IN ADDITION...MID LEVEL TEMPS SHOULD COOL ON SATURDAY NIGHT AS THE MID/UPPER LEVEL TROUGH BEGINS TO TAKE SHAPE. THIS WOULD YIELD STEEP LAPSE RATES THROUGH ABOUT 700MB AND SIGNIFICANT CAPE LATE SUNDAY AND SUNDAY EVENING...POSSIBLY SUPPORTING A SEVERE WX THREAT...ESPECIALLY CONSIDERING THE FAVORABLE WIND FIELDS IN FORECAST SOUNDINGS. THE COLD FRONT ASSOCIATED WITH THE LONGWAVE TROUGH IS EXPECTED TO PASS SUNDAY NIGHT...ALLOWING A MUCH COOLER AIR MASS TO ARRIVE. EVEN SO...WITH MUCH COOLER AIR ALOFT...FORECAST SOUNDINGS STILL SUGGEST SHOWERS OR THUNDERSTORMS COULD DEVELOP WITH HEATING ON MONDAY AS RESIDUAL LOW LEVEL MOISTURE MIXES AWAY AND GETS SCOURED OUT. HAVE CARRIED 20-30 PERCENT POPS ON MONDAY INTO MONDAY EVENING. DRIER AIR WILL FINALLY MAKE IT HERE AT MIDWEEK...AND PLEASANT AND UNSEASONABLY COOL WEATHER IS FORECAST FOR TUESDAY INTO THURSDAY. MODELS SHOW ANOTHER SHORTWAVE DROPPING INTO THE LARGE TROUGH...AND PASSING THROUGH OUR AREA ON THURSDAY. MODELS GENERATE PRECIP...BUT WITH LITTLE MOISTURE RECOVERY...HAVE OPTED TO USE NOTHING HIGHER THAN 20 PERCENT POPS...AND ONLY IN OUR SE COUNTIES.
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&& .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED AT 125 AM EDT FRI JUL 25 2014 ALTHOUGH IT WILL BE HALTING AND STAGGERED THROUGH THE NIGHT...THE TREND IN THE CONDITIONS AT THE TAF SITES WILL BE DOWNWARD. ACCORDINGLY...HAVE TAKEN THEM DOWN TO VLIFR FOR A TIME TOWARD DAWN WITH SOME TEMPOS ON THE WAY DOWN. THE FOG WILL CLEAR BY MID MORNING WITH JUST SOME VFR FAIR WEATHER CU LEFT BEHIND INTO THE AFTERNOON. WINDS WILL REMAIN LIGHT AND VARIABLE THROUGH THE FORECAST PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...HAL AVIATION...GREIF

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