Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 010705 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 305 AM EDT SAT AUG 1 2015 .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 305 AM EDT SAT AUG 1 2015 06Z SFC ANALYSIS SHOWS THAT HIGH PRESSURE REMAINS IN CONTROL OF EAST KENTUCKY/S WEATHER THIS EARLY MORNING. THIS HIGH HAS KEPT CLOUD COVER TO A MINIMUM AND IS SUPPORTING A DECENT RIDGE TO VALLEY TEMPERATURE SPLIT ON THE ORDER OF 5 TO 10 DEGREES. AT THE SAME TIME DEWPOINTS ARE RUNNING IN THE LOWER 60S. AS TEMPERATURES CONTINUE TO RADIATE LOWER FOR THE REST OF THE NIGHT THE DEWPOINTS WILL ALSO CREEP DOWN...BUT IN THE DEEPER VALLEYS PROBABLY NOT FAST ENOUGH TO PREVENT THE DEVELOPMENT OF FOG...ESPECIALLY NEAR RIVERS AND BODIES OF WATER. WINDS WILL BE LIGHT THROUGH DAWN PERHAPS CONTRIBUTING TO THE LOCALLY DENSE FOG IN THE MORE SHELTERED RIVER VALLEY SPOTS. THE MODELS ARE IN GOOD AGREEMENT ALOFT WITH THE LONGWAVE PATTERN AS THEY ALL DEPICT A SLOWLY DEEPENING...LARGE TROUGH THROUGH THE NORTHEAST PORTION OF THE CONTINENT STRETCHING SOUTH THROUGH THE OHIO VALLEY OVER THE WEEKEND. THE NORTHWEST FLOW ASSOCIATED WITH THIS WILL BRING MINOR SHORTWAVES OVER KENTUCKY DURING THE PERIOD BUT NOT MUCH IN THE WAY OF MESOSCALE AMPLIFICATION UNTIL PERHAPS SUNDAY AFTERNOON WHEN A HEALTHIER ONE PASSES BY TO THE NORTH. THE NAM CONTINUES TO BE ON THE STRONGER SIDE OF THE MODEL SPECTRUM WITH THE LARGER TROUGH AND THIS WAVE LATE IN THE PERIOD. ACCORDINGLY...HAVE GONE WITH MORE OF A MODEL BLEND FAVORING A MIX OF THE ECMWF AND GFS OUTSIDE OF THE NEAR TERM WHERE THE HRRR AND NAM12 ARE REASONABLE. SENSIBLE WEATHER WILL FEATURE A VERY PLEASANT MID SUMMER WEEKEND AS THE AFTERNOON WARMTH IS KEPT COMFORTABLE BY RELATIVELY LOW HUMIDITIES WROUGHT BY A MIDDAY AND AFTERNOON MIX DOWN OF DRIER AIR FROM THE MID LEVELS. THIS WILL KEEP CLOUD COVER TO A MINIMUM THROUGH THE PERIOD AND ALSO LEAD TO ANOTHER NIGHT OF GOOD RADIATIONAL COOLING FOR SUNDAY MORNING. SIMILARLY...PATCHY FOG WILL LIKELY BE LIMITED TO THE DEEPER RIVER VALLEY LOCATIONS BOTH THIS MORNING AND SUNDAY MORNING...THOUGH LOCALLY DENSE POCKETS WILL BE POSSIBLE AS WELL. AGAIN USED THE SHORTBLEND MODEL AS A STARTING POINT FOR THE T/TD/WIND GRIDS THROUGH THE DAY FOLLOWED BY THE SUPERBLEND INTO SUNDAY. DID MAKE SOME SIGNIFICANT ADJUSTMENTS TO TEMPERATURES THIS MORNING AND TONIGHT WITH RESPECT TO RIDGE AND VALLEY DIFFERENCES ONCE...AND AS...THE INVERSION IS IN PLACE. AS FOR POPS...KEPT THEM LOW AND IN LINE WITH THE DRIER MET GUIDANCE. .LONG TERM...(SUNDAY THROUGH FRIDAY) ISSUED AT 344 PM EDT FRI JUL 31 2015 THE PERIOD IS EXPECTED TO BEGIN WITH A RIDGE EXTENDING FROM THE SOUTHERN PLAINS INTO THE CENTRAL ROCKIES AND A TROUGH TROUGH OVER MUCH OF THE EASTERN CONUS EXTENDING SOUTH FROM A CLOSED LOW OVER THE SOUTHERN HUDSON BAY REGION. AT THAT POINT...A FEW SHORTWAVES WILL BE MOVING INTO THE TROUGH ACROSS THE GREAT LAKES REGION. A FEW SHORTWAVES WILL ALSO BE WORKING AROUND THE RIDGE ACROSS THE WESTERN CONUS TO START THE PERIOD...WITH ANOTHER FURTHER NORTH MOVING INTO SOUTHWESTERN CANADA. AT THE SFC...HIGH PRESSURE IS EXPECTED TO BE CENTERED OVER THE CENTRAL APPALACHIANS AT THAT POINT...WITH SFC LOW PRESSURE ALSO CENTERED OVER THE SOUTHERN HUDSON BAY REGION AND A COLD FRONT EXTENDING SOUTH INTO THE NORTHERN GREAT LAKES AND NORTHERN PLAINS...BEFORE BECOMING STATIONARY AND EXTENDING NORTHWEST INTO THE NORTHERN ROCKIES. THE CLOSED LOW INITIALLY NEAR SOUTHERN HUDSON BAY SHOULD MEANDER SOUTH AND SOUTHEAST INTO ONTARIO AND QUEBEC AND OPEN UP A BIT THROUGH THE EARLY TO MIDDLE PART OF NEXT WEEK. A SHORTWAVE OR TWO ROTATING AROUND THIS LOW SHOULD WORK INTO THE NORTHERN GREAT LAKES TO END THE WEEKEND AND ROTATE THROUGH THE GREAT LAKES AND INTO THE NORTHEASTERN STATES THROUGH TUESDAY. THEN A SHORTWAVE WORKING AROUND THE RIDGE SHOULD APPROACH THE MS RIVER VALLEY. THE MODELS ARE NOT IN AGREEMENT WITH THE EVOLUTION AND TIMING OF THE SHORTWAVE ENTERING SOUTHWEST CANADA EARLY IN THE PERIOD WORKING INTO SOUTHWEST CANADA THE CORRESPONDING SFC AREA OF LOW PRESSURE SHOULD TRACK INTO QUEBEC WITH THE TRAILING COLD FRONT GRADUALLY DROPPING SOUTH OF THE GREAT LAKES DURING THE MONDAY INTO TUESDAY PERIOD...BEFORE STALLING OUT AND BECOMING NEARLY STATIONARY NEAR THE OHIO RIVER. THE SHORTWAVE MOVING INTO THE MS VALLEY AROUND MIDWEEK SHOULD LEAD TO A SFC WAVE OR WAVES DEVELOPING ALONG THIS BOUNDARY AND MOVING THROUGH THE OHIO VALLEY REGION. THE FRONTAL ZONE ITSELF COULD ALSO PASS THROUGH THE AREA LATE IN THE PERIOD. OVERALL...THE EXPECTED SFC AND UPPER AIR PATTERN WILL LEAVE THE REGION SUSCEPTIBLE TO AT LEAST DIURNALLY DRIVEN CONVECTION AND POSSIBLE MCS OR NOCTURNAL ACTIVITY. THE NORTHERN AND EASTERN PARTS OF THE AREA MAY BE IMPACTED EARLY IN THE WEEK...POSSIBLY AS EARLY AS THE START OF THE WORK WEEK. AS FOR POPS...SUNDAY IS EXPECTED TO BRING A DRY END TO THE WEEKEND. ISOLATED TO SCATTERED CONVECTION CANNOT BE RULED OUT AT ANY POINT FROM MONDAY TO POSSIBLY AS LATE AS FRIDAY. THE TRACK AND TIMING OF THE SHORTWAVE THAT ENTERS SW CANADA EARLY IN THE PERIOD WILL PLAY A KEY ROLE IN THE DURATION OF THE THREAT FOR CONVECTION. WITH THE MODELS RELATIVELY IN GOOD AGREEMENT THROUGH ABOUT THURSDAY WITH THE SFC AND UPPER AIR PATTERN AND THE SHORTWAVE EXPECTED TO NEAR AT MIDWEEK...CHANCES FOR CONVECTION APPEAR GREATEST FROM WED INTO THU. TEMPERATURES SHOULD MODERATE TO A FEW DEGREES ABOVE NORMAL DURING THE MONDAY INTO WEDNESDAY PERIOD...BEFORE THE COLD FRONT GRADUALLY SLIPS SOUTH. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT 230 AM EDT SAT AUG 1 2015 HIGH PRESSURE WILL KEEP VFR CONDITIONS IN THE TAF FORECAST FOR MOST OF THE SITES THROUGH THE PERIOD. THE EXCEPTION MAY BE AT SME LATE THIS NIGHT AS THEIR DEWPOINT DEPRESSION IS CURRENTLY THE SMALLEST. ACCORDINGLY...HAVE ADDED A PERIOD OF MVFR FOG TO THAT SITE WHILE LEAVING THE REST CLEAN. OUTSIDE OF THE FORMAL TAF SITES...PATCHY FOG WILL BE FOUND IN THE LOWER ELEVATIONS TOWARDS DAWN...BECOMING LOCALLY DENSE FOR A BRIEF TIME. ANY FOG WILL CLEAR OUT BY MID MORNING WITH VFR CONDITIONS CONTINUING INTO SATURDAY NIGHT AT THE AIRPORTS. WINDS THROUGH THE PERIOD WILL BE LIGHT AND VARIABLE. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...JP AVIATION...GREIF

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