Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200241 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1041 PM EDT TUE MAY 19 2015 .UPDATE...
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ISSUED AT 1041 PM EDT TUE MAY 19 2015 SOME OF THE MORE SHELTERED VALLEYS HAVE STARTED TO DECOUPLE...WITH SOME SPOTS DOWN INTO THE MID 50S. GIVEN THE CURRENT TRENDS...EXPECT UP TO ANOTHER 10 DEGREE DROP OR SO THROUGH THE REST OF THE NIGHT. AS SUCH...DID NUDGE UP SOME OF THE READINGS...PARTICULARLY THE RIDGETOPS AND BROADER VALLEYS...WHERE MIXING WILL BATTLE THE RADIATIONAL COOLING. THIS WILL LIKELY KEEP MOST OF THESE SITES ABOVE THE 50 DEGREE MARK...WHILE THE MORE SHELTERED LOCATIONS DIP INTO THE 40S. UPDATES WILL BE SENT SHORTLY. UPDATE ISSUED AT 809 PM EDT TUE MAY 19 2015 FLATTENED CUMULUS HAVE DISSIPATED AS WE HEAD TOWARDS SUNSET. FORECAST LOWS LOOK REASONABLE AND WILL ONLY ALLOW FOR SOME TOUCH UPS ON THE HOURLY TEMPERATURE AND DEW POINT CURVES TO ACCOUNT FOR THE CURRENT TRENDS IN OBSERVATIONS.
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&& .SHORT TERM...
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(THIS EVENING THROUGH WEDNESDAY NIGHT) ISSUED AT 314 PM EDT TUE MAY 19 2015 A COLD FRONT CONTINUES TO DEPART TO THE SOUTH AND EAST OF THE REGION AS OF MID AFTERNOON WITH LOW LEVEL MOISTURE LEFT BEHIND WEST OF THE CREST OF THE APPALACHIANS. SKIES HAVE CLEARED FROM NEAR THE INTERSTATE 64 CORRIDOR NORTHWEST WHILE CU AND STRATOCU REMAIN ACROSS THE REMAINDER OF THE AREA. DRIER AIR CONTINUES TO GRADUALLY FILTER INTO THE REGION AS SFC HIGH PRESSURE CENTERED OVER THE NORTHERN PLAINS REGION NOSES INTO THE LOWER OH VALLEY REGION. AT MID LEVELS...A WEAK SHORTWAVE RIDGE WAS WORKING INTO THE REGION AS WELL. MEANWHILE... FURTHER TO THE WEST...A MID LEVEL SHORTWAVE WAS WORKING FROM THE ROCKIES INTO THE PLAINS STATES. THROUGH THE PERIOD...THE SFC HIGH IS EXPECTED TO SHIFT SOUTH INTO THE CENTRAL PLAINS WITH RIDGING EXTENDING EAST INT THE OH VALLEY REGION. MEANWHILE...THE MID LEVEL WAVE IS EXPECTED TO MOVE EAST THROUGH THE PERIOD AND APPROACH THE LOWER OH VALLEY AS IT MOVES WITHIN A GENERALLY ZONAL PATTERN FROM THE ROCKIES INTO THE EASTERN CONUS. THIS SHORTWAVE WILL WORK ACROSS THE REGION AT THE END OF THE PERIOD INTO VERY EARLY IN THE LONG TERM PERIOD. CU SHOULD CONTINUE TO LIFT AND MIX OUT FOR THE REMAINDER OF THE AFTERNOON INTO THE EVENING HOURS. THE MID LEVEL RIDGING AND SFC HIGH SHOULD BRING CLEAR OR MOSTLY CLEAR SKIES TO THE REGION TONIGHT ALONG WITH SLACKENING WINDS. THIS WILL SET THE STAGE FOR A SMALL TO POSSIBLY MODERATE RIDGE/VALLEY SPLIT...ESPECIALLY ACROSS THE NORTH AND WESTERN PARTS OF THE REGION. WITH THE DRIER AIR HAVING ALREADY ADVECTED INTO THE NORTHWESTERN PART OF THE REGION AND THE DRIER AIR BEING SLOWER TO WORK INTO THE SOUTHEAST...IT APPEARS THAT THE STAGE WILL LIKELY BE SET FOR SOME RIVER VALLEY FOG IN THE NORTHWEST AND VALLEY FOG IN THE SOUTHEAST. SOME OF THE VALLEY FOG IN THE SOUTHEAST COULD BE DENSE SINCE DEW POINTS ACROSS MUCH OF THAT AREA ARE STILL IN THE UPPER 50S TO LOWER 60S. THE COLDEST LOWS TONIGHT SHOULD BE IN VALLEY LOCATIONS GENERALLY NORTH OF THE MTN PARKWAY...WHERE SOME LOW TO MID 40S WILL BE POSSIBLE... WHILE FURTHER SOUTH VALLEY LOCATIONS SHOULD RANGE FROM THE MID 40S TO AROUND 50. RIDGETOP LOCATIONS ARE EXPECTED TO REMAIN AROUND 50 OR IN THE LOWER 50S. MID AND HIGH LEVEL MOISTURE WILL BEGIN TO INCREASE TOMORROW... ESPECIALLY LATE IN THE DAY AHEAD OF THE APPROACHING SHORTWAVE TROUGH. THE CLOUDS SHOULD THICKEN MORE QUICKLY ACROSS THE NORTH AND WEST AND GIVEN A NORTH TO SOUTH GRADIENT IN 850 MB TEMPERATURES IN THE ZONAL PATTERN...HIGHS ON WED ARE EXPECTED TO HAVE A GENERAL NORTH TO SOUTH GRADIENT OF POSSIBLY MORE THAN 10 DEGREES...REACHING THE UPPER 60S TO AROUND 70 IN THE FAR NORTH AND NEARING THE 80 DEGREE MARK NEAR THE TN BORDER. THERE REMAINS MODEL DISAGREEMENT BETWEEN THE CONSTANTLY DRIER GFS AND MUCH OF THE OTHER GUIDANCE SUCH AS THE NAM AND ECMWF FOR RAIN CHANCES AS THE SHORTWAVE WORKS THROUGH THE AREA ON WED NIGHT. WITH ALL THE NON GFS GUIDANCE STILL BRINGING IN SOME PRECIPITATION TO THE REGION...THE SREF POPS RATHER HIGH...AND THE MODEL BLENDS HIGHER THAN THE PREVIOUS FORECAST...POPS WERE RAISED TO ABOUT 40 PERCENT FOR WED NIGHT. IF THE GFS GUIDANCE ALSO FALLS IN LINE WITH BEING A BIT WETTER POPS MAY NEED TO BE RAISED FURTHER. ATTM...THE PRECIP TYPE WAS KEPT AS JUST SHOWERS AS INSTABILITY APPEARS TO LOW FOR ANY CHANCES OF THUNDER. RAINFALL WHERE RAIN DOES OCCUR WITH THIS SYSTEM SHOULD BE RATHER LIGHT...NO MORE THAN A TENTH TO QUARTER OF AN INCH IF THAT. WITH CLOUDS AND RAIN CHANCES LOWS ON WED NIGHT SHOULD BE IN GENERAL MORE UNIFORM ACROSS THE AREA AND MILDER THAN TONIGHT. .LONG TERM...(THURSDAY THROUGH TUESDAY) ISSUED AT 250 PM EDT TUE MAY 19 2015 THE EXTENDED PERIOD STARTS WITH AN UPPER LEVEL TROUGH PASSING TO OUR NORTH ON THURSDAY MORNING...BRINGING A CHANCE FOR PRECIP TO OUR AREA. STILL SOME DIFFERENCES IN THE MODELS BUT NOW THE DRY GFS IS THE OUTLIER...SO HAVE DECIDED TO TRANSITION OVER TO SLIGHT POPS FROM WEST TO EAST INTO THURSDAY EVENING. HIGHER HEIGHTS THEN BUILD INTO THE REGION ON FRIDAY AS A SFC AND UPPER LEVEL RIDGE TAKES HOLD OF THE EASTERN US. THIS WILL ALLOW FOR BEAUTIFUL WEATHER FOR THE FIRST HALF OF MEMORIAL DAY WEEKEND. BY SUNDAY...SOUTHERLY FLOW SETS UP AHEAD OF A DEVELOPING SOUTHERN PLAINS LOW PRESSURE SYSTEM. THIS RETURN FLOW INCREASES MOISTURE IN THE REGION AND ALLOWS FOR DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS EACH AFTERNOON THROUGH THE END OF THE PERIOD. TEMPERATURES WILL GENERALLY HOVER AROUND THE 80 DEGREE MARK THROUGH THE PERIOD WITH THE EXCEPTION OF THURSDAY AND FRIDAY WHERE LOWS WILL BE IN THE UPPER 40S/LOW 50S AND AFTERNOON HIGHS WILL REACH THE LOW TO MID 70S. OTHERWISE...OVERNIGHT LOWS WILL BE ON THE MILD SIDE...IN THE LOWER 60S...SUNDAY ONWARD.
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&& .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING) ISSUED AT 809 PM EDT TUE MAY 19 2015 HIGH PRESSURE WILL BUILD IN ACROSS THE OHIO VALLEY TONIGHT... ALLOWING FOR MAINLY VFR CONDITIONS. THERE WILL LIKELY BE SOME PATCHY IFR OR WORSE FOG BETWEEN 06 AND 13Z...HOWEVER THIS WILL BE RESTRICTED TO THE DEEPER RIVER VALLEYS. HIGH CLOUDS WILL BE ON THE INCREASE DURING THE DAY ON WEDNESDAY...AS AN UPPER LEVEL DISTURBANCE APPROACHES FROM THE NORTHWEST. WINDS WILL REMAIN IN THE 5 TO 10 KT RANGE...GENERALLY FROM THE NORTHEAST. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...JVM AVIATION...GEOGERIAN

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