Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 280248 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1048 PM EDT SAT SEP 27 2014 .UPDATE...
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ISSUED AT 1048 PM EDT SAT SEP 27 2014 MOSTLY CLEAR SKIES ARE HOLDING ACROSS EASTERN KENTUCKY. THICKER HIGH CLOUDS ARE BEGINNING TO STREAM IN ACROSS SOUTHWEST TN/KY...AND THESE WILL EVENTUALLY MOVE IN ACROSS OUR AREA DURING THE OVERNIGHT. THE FORECAST LOWS LOOK TO BE IN GOOD SHAPE OVERALL AND HAVE ONLY MADE A FEW MINOR ADJUSTMENTS...MAINLY AT SOME OF THE RIDGETOP LOCATIONS. LIGHT WINDS ARE ALREADY ALLOWING FOR A DECENT RIDGE/VALLEY TEMPERATURE SPLIT IN PLACES...SO HAVE ADJUSTED SOME OF THE RIDGETOP LOWS UP A BIT...GENERALLY IN THE LOW 60S...WHILE THE VALLEYS DIP DOWN INTO THE MID AND UPPER 50S. UPDATE ISSUED AT 820 PM EDT SAT SEP 27 2014 THE FORECAST REMAINS ON TRACK TONIGHT. MERELY FRESHENED UP THE HOURLY TEMPERATURES AND DEW POINTS TO ACCOUNT FOR THE LATEST TRENDS IN OBSERVATIONS.
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&& .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 328 PM EDT SAT SEP 27 2014 AS OF MID AFTERNOON...MUCH OF THE EASTERN CONUS WAS UNDER THE INFLUENCE OF A RIDGE OF HIGH PRESSURE EXTENDING FROM OFF THE SOUTHEASTERN US COAST NORTH INTO THE GREAT LAKES REGION. MEANWHILE AN UPPER LEVEL TROUGH WAS IN PLACE ACROSS THE WESTERN CONUS. A WEAK UPPER LEVEL TROUGH/LOW WAS CENTERED OVER WESTERN IA WITH ANOTHER WEAK TROUGH IN PLACE ACROSS THE SOUTHERN PLAINS REGION. A MORE SIGNIFICANT TROUGH IS WORKING THROUGH THE NORTHERN STREAM...WELL TO THE NORTH OF THE US/CANADIAN BORDER. AT THE SFC...HIGH PRESSURE WAS IN PLACE ACROSS THE CENTRAL GREAT LAKES REGION...WITH RIDGING INTO THE MID MS VALLEY REGION AND SOUTH ALONG ALONG THE EASTERN SEABOARD. AN INVERTED TROUGH EXTENDED NORTH INTO THE MIDDLE TN REGION AND NORTH INTO CENTRAL KY. THE UPPER LEVEL RIDGE AXIS WILL SHIFT TO THE EASTERN SEABOARD WITH UPPER LEVEL TROUGH OVER IA BEGINNING TO MERGE WITH THE NORTHERN STREAM TROUGH AND THE SOUTHERN PLAINS TROUGH BEGINNING TO MOVE EAST NORTHEAST TONIGHT. HEIGHTS ARE EXPECTED TO FALL ACROSS THE WESTERN GULF OF MEXICO AND WEAK SFC LOW PRESSURE BEGINNING TO DEVELOP. ON SUNDAY THE AXIS OF THE UPPER LEVEL TROUGH/THE COMBINATION OF THE TWO UPPER LEVEL SYSTEMS NW TO OUR NW AND SW WILL MOVE TO THE MS VALLEY REGION. THE UPPER LEVEL TROUGH AXIS WILL MOVE TO A LINE FROM WESTERN LAKE ERIE SOUTH INTO THE MS DELTA REGION ON SUNDAY NIGHT...WITH THE AXIS OF THE TROUGH NEARING CENTRAL KY BY THE END OF THE PERIOD. AT THE SFC...LOW PRESSURE IS EXPECTED TO ORGANIZE AND TRACK INTO THE SOUTHERN MS/NW FLORIDA REGION BY DAWN ON MONDAY. AN INVERTED TROUGH IS EXPECTED TO EXTEND NORTH INTO THE COMMONWEALTH FROM THIS LOW. AS THE LOW PRESSURE SYSTEM BEGINS TO DEVELOP TO OUR SOUTH AND THE UPPER LEVEL TROUGH APPROACHES AND THE UPPER LEVEL RIDGE DEPARTS...A GRADUAL INCREASE IN CLOUDS IS EXPECTED TONIGHT THROUGH MID AFTERNOON ON SUNDAY. PATCHY VALLEY FOG SHOULD AGAIN DEVELOP TONIGHT...AND MAY BECOME DENSE IN A FEW LOCATIONS. OTHERWISE...THE INCREASE IN CLOUDS WILL INITIALLY BE MOSTLY OF THE HIGH VARIETY...WITH LOWER LEVEL MOISTURE INCREASING ON SUNDAY AND INTO SUNDAY NIGHT. THE MODELS CONTINUE TO VARY AS TO HOW FAR NORTH AND WEST RAIN ASSOCIATED WITH THE EASTERN GULF OF MEXICO/SOUTHEASTERN CONUS LOW WILL GET. EVEN THE 12Z ECMWF TRENDED MORE TO THE SOUTHEAST COMPARED TO BEING MORE AGGRESSIVE ON ITS 0Z RUN. AT THIS POINT...POPS WERE KEPT NEARLY THE SAME FOR SUNDAY...WITH SOME SLIGHT CHANCE POPS FROM LATE AFTERNOON INTO THE EVENING...ACROSS THE SOUTHWEST AND WEST. THE MAIN RAIN CHANCES FROM THIS SYSTEM WILL COME LATER ON SUNDAY NIGHT AND INTO THE START OF THE LONG TERM PERIOD. A COMPROMISE OF LOWER POPS ACROSS NW AND CENTRAL THIRD OF THE CWA...AND SHARPENED UP THE POP GRADIENT CLOSER TO THE VA BORDER. THIS CONFINED 50 TO 60 PERCENT POPS CLOSER TO THE VA BORDER. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 316 PM EDT SAT SEP 27 2014 THE MODELS WERE PRETTY GOOD AGREEMENT TO BEGIN THE EXTENDED PERIOD. THE BULK OF THE MODELS ARE DEVELOPING AN AREA OF LOW PRESSURE ALONG THE CENTRAL GULF COAST SUNDAY NIGHT...AND MOVING THIS FEATURE ACROSS THE SOUTHEASTERN CONUS AND THEN OUT TO SEE OF THE SOUTHEAST COAST TUESDAY NIGHT. THE ISSUE AT HAND IS HOW FAR NORTHWEST THE MODELS ARE TRACKING THIS AREA OF LOW PRESSURE. MOST OF THE MODELS KEEP MOST OF THE PRECIPITATION ASSOCIATED WITH THIS SYSTEM OFF TO OUR SOUTHEAST. THE SREF AND ECMWF MODELS...HOWEVER...ARE ALLOWING A BIT OF PRECIPITATION TO WORK INTO THE AREA ON MONDAY. THAT BEING SAID...THE DECISION WAS MADE TO GO WITH THE COMBINED SREF AND ECMWF SOLUTIONS TO CONSTRUCT THE FORECAST FOR PRECIPITATION CHANCES...RAINFALL AMOUNTS...AND CLOUD COVER TO BEGIN THE PERIOD. WITH GOOD AGREEMENT AMONGST THE MODELS FROM TUESDAY ONWARD...THE REMAINDER OF THE WEEKS WEATHER WAS HANDLED BY THE TRIED AND TESTED ECMWF MODEL. THE HIGHEST RAIN CHANCES WILL LIKELY OCCUR ALONG THE VIRGINIA AND WEST VIRGINIA BORDERS WHERE THE PREFERRED MODELS WERE SUGGESTING. THE PRECIPITATION WE RECEIVE ON MONDAY SHOULD REMAIN IN THE FORM OF ORDINARY RAIN SHOWERS...AS WE WILL BE ON THE COOL SIDE OF THE PASSING LOW PRESSURE AND INSTABILITY WILL BE QUITE LACKING. AFTER MONDAY EVENING...A RIDGE OF HIGH PRESSURE IS EXPECTED BUILD OVER THE REGION THROUGH THE END OF THE WEEK. THE WEATHER LOOKS TO BE WARM BUT SEASONABLE DURING THIS TIME...WITH HIGHS EACH DAY TOPPING IN THE MID TO UPPER 70S. A SECOND WEATHER SYSTEM IS THEN PROGGED TO MOVE ACROSS THE AREA ON FRIDAY IN THE FORM OF A STRONG SURFACE COLD FRONT. THE ECMWF AND GFS MODELS BOTH WERE IN DECENT AGREEMENT WITH THE HANDLING OF THIS SYSTEM...WITH THE ECMWF BEING ONLY SLIGHTLY FASTER WITH THE EASTWARD PROGRESSION OF THIS FRONT THAT THE GFS. ALL IN ALL IT APPEARS THAT ISOLATED RAIN SHOWERS COULD BEGIN MOVING INTO THE AREA EARLY FRIDAY MORNING...WITH SCATTERED SHOWERS AND A FEW THUNDERSTORMS POSSIBLE ONCE THE SUN IS UP AND BEGINS HEATING THE LOWER LEVELS OF THE ATMOSPHERE GIVING US A BIT OF INSTABILITY AHEAD OF THE APPROACHING FRONT. THE FRONT ITSELF SHOULD PUSH ACROSS THE AREA FAIRLY QUICKLY...WITH THE WIND SHIFTING FROM THE SOUTH TO WEST BY EARLY FRIDAY EVENING AS THE FRONT PASSES BY. DUE TO THIS...AND THE INFLUENCE OF CLOUDS AND PRECIPITATION...DAY TIME HIGHS ON FRIDAY WOULD LIKELY BE QUITE A BIT COOLER THAN THE REST OF THE WEEK. HIGHS ON FRIDAY MIGHT ONLY MAKE IT INTO THE LOW TO MID 70S AREA WIDE AS COOLER AIR ASSOCIATED WITH A LARGE RIDGE OF CANADIAN HIGH PRESSURE BUILDS INTO THE AREA FROM THE NORTHWEST. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING) ISSUED AT 820 PM EDT SAT SEP 27 2014 PATCHY DENSE FOG WILL BE THE FIRST CONCERN THROUGH THE OVERNIGHT. EXPECT MOST OF THE LIFR OR WORSE FOG TO STEER CLEAR OF THE MAJORITY OF THE TAF SITES AND STAY MORE CONFINED TO THE DEEPER RIVER VALLEYS. ONE EXCEPTION MAY BE SJS AND WILL MAINTAIN A SMALL PERIOD OF LIFR FOG...HOWEVER WITH THE WINDS VEERING AROUND TO THE SOUTHEAST OVERNIGHT...COULD SEE EVEN THIS LOCATION AVOIDING THE LIFR OR WORSE CONDITIONS AS WELL. ONCE THE FOG BURNS OFF THROUGH 13Z...CLOUDS WILL BE LOWERING OUT AHEAD OF AN APPROACHING MID-LEVEL DISTURBANCE. A FEW SHOWERS WILL BE POSSIBLE DURING THE DAY...ESPECIALLY ALONG AND SOUTH OF THE HAL ROGERS PARKWAY AND HIGHWAY 80 CORRIDORS. WILL MAINTAIN VFR CONDITIONS FOR NOW. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...AR AVIATION...GEOGERIAN

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