Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 230539 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 139 AM EDT WED JUL 23 2014 .UPDATE... ISSUED AT 139 AM EDT WED JUL 23 2014 CONDITIONS ACROSS THE AREA REFLECT THE CURRENT FORECAST QUITE WELL. PERHAPS SOME LESSENING OF THE CLOUD COVER IS IN ORDER AS THE MORE WIDE SPREAD COVER IS STILL UP STREAM. OTHERWISE...THE CURRENT FORECAST REMAINS ON TRACK AND HAVE UPLOADED THE CURRENT OBS INTO THE GRIDS. UPDATE ISSUED AT 1040 PM EDT TUE JUL 22 2014 THE SHOWERS HAVE DRIED UP ACROSS THE ENTIRE AREA BESIDES A SMALL CELL OVER NORTHERN PULASKI COUNTY. THIS WILL DIMINISH THROUGH 11 PM...LEAVING MOSTLY CLEAR TO PARTLY CLOUDY SKIES OVERHEAD FOR THE MAJORITY OF THE OVERNIGHT. EXPECT MOISTURE TO INCREASE BETWEEN 4 AND 8 AM...WITH PERHAPS A SMALL UPTICK IN CONVECTIVE ACTIVITY THREATENING ALONG THE SOUTHEAST TERRAIN. THE LATEST HRRR IS SUGGESTING SOME ACTIVITY MAKING IT IN FROM THE NORTHWEST BEFORE DAWN...HOWEVER THE CONVECTIVE OUTCOME LOOKS A BIT QUICK ACCORDING TO THE LATEST SATELLITE TRENDS...SO STUCK WITH THE INHERITED DRY POPS IN THE BLUEGRASS FOR NOW. BALMY LOWS OF AROUND THE 70 DEGREE MARK FOR MOST LOCATIONS STILL LOOK ON TARGET. DID INCORPORATE THE LATEST HOURLY OBSERVATIONS INTO THE DIURNAL DROP OFF FOR THE REST OF THE NIGHT. UPDATES HAVE BEEN SENT. UPDATE ISSUED AT 817 PM EDT TUE JUL 22 2014 CONVECTION IS ON THE DECLINE WITH THE LOSS OF HEATING. WILL HANG ONTO ISOLATED SHOWERS AND A RUMBLE OF THUNDER FOR ANOTHER HOUR OR TWO... BEFORE A LULL IS THEN EXPECTED INTO THE OVERNIGHT. AS WEAKER SOUTHWEST FLOW ENGAGES IN TH LOW LEVELS TOWARDS DAWN...THERE MAY BE A SMALL INCREASE IN CONVECTION ONCE AGAIN...WHICH THE CURRENT FORECAST ALREADY HAS WELL IN HAND. UPDATES HAVE BEEN SENT. && .SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT) ISSUED AT 420 PM EDT TUE JUL 22 2014 AS OF LATE AFTERNOON...AN UPPER LEVEL LOW IS MEANDERING ALONG THE GULF COAST WHILE THE EASTERN EXTENT OF AN UPPER LEVEL RIDGE CENTERED NEAR THE FOUR CORNERS REGION EXTENDS INTO THE LOWER OH VALLEY REGION. A SHORTWAVE IS ROTATING ACROSS THE NORTHERN GREAT LAKES AND ONTARIO WITH ANOTHER UPSTREAM ENTERING NORTHWEST ONTARIO. THE SHORTWAVES WILL COMBINE TO HELP FORM AN EASTERN CONUS TROUGH THROUGH THE PERIOD WHILE THE RIDGE AMPLIFIES ACROSS THE ROCKIES. A SFC LOW ASSOCIATED WITH THE DEVELOPING TROUGH WILL TRACK FROM JUST NORTH OF THE NORTHERN GREAT LAKES AND INTO THE MARITIMES THROUGH WED NIGHT WITH THE DEVELOPING TROUGH AND NORTHWEST FLOW PUSHING THE TRAILING COLD FRONT INTO THE OH VALLEY LATE TONIGHT INTO THE DAY ON WED. THIS FRONT WILL GRADUALLY CROSS THE REGION LATE ON WED AFTERNOON INTO WED EVENING. IN THE MEANTIME...ISOLATED SHOWERS AND POSSIBLY A STRAY THUNDERSTORM WILL REMAIN POSSIBLE MAINLY UNTIL NEAR SUNSET AND DAYTIME HEATING IS LOST. THERE WILL BE SOME MINOR HEIGHT FALLS OVERNIGHT AND WITH A MOIST AIR MASS IN PLACE...A STRAY SHOWER CANNOT BE RULED OUT OVERNIGHT...BUT THIS WOULD BE FEW AND FAR BETWEEN OTHERWISE...THE CONSECUTIVELY DRIVEN CU SHOULD DISSIPATE OVERNIGHT AND PATCHY RIVER VALLEY FOG IS AGAIN ANTICIPATED. MORE ORGANIZED CONVECTION IS ANTICIPATED AS THE FRONT APPROACHES AND CROSSES THE REGION AND THE UPPER LEVEL TROUGH DEVELOPS OVER THE EASTERN CONUS. THIS FRONT AND UPPER LEVEL FORCING FROM THE DEVELOPING TROUGH WILL INTERACT WITH A MOIST PREFONTAL AIR MASS TO BRING MORE ORGANIZED CONVECTION TO THE REGION FROM WED AFTERNOON INTO WED NIGHT. MORNING HEATING WILL BE DE PENDANT ON HOW MUCH CLOUD COVER THERE IS IN THE AM AND THIS WILL ULTIMATELY DETERMINE INSTABILITY. MODERATE INSTABILITY IS ANTICIPATED WITH TEMPS IN THE MID 80S TO AROUND 90 AND DEWPOINTS IN THE UPPER 60S TO AROUND 70. THE LOW LEVEL GRADIENT WILL BE RATHER WEAK AND SO WILL THE WINDS WHILE THE UPPER LEVEL WINDS WILL NOT BE ALL THAT STRONG SO SHEAR WILL BE WEAK. PWS IS PROGGED TO CLIMB 1.5 TO 1.8 INCH RANGE FROM MIDDAY WED INTO WED NIGHT...SO STORMS SHOULD BE ABLE TO PRODUCE LOCALLY HEAVY RAIN. A STRONGER STORM OR TWO MIGHT ALSO BE ABLE TO PRODUCE STRONG WIND GUSTS. ONCE THE FRONT CROSSES THE REGION...INSTABILITY WILL DIMINISH AND THE THREAT FOR THUNDER SHOULD ALSO DIMINISH LATE WED NIGHT. TEMPS WILL CONTINUE TO BE ABOVE NORMAL THROUGH THE PERIOD...BUT A COLDER AND DRIER AIR MASS WILL ALREADY BE STARTING TO ADVECT INTO THE AREA LATE IN THE PERIOD. .LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY) ISSUED AT 348 AM EDT TUE JUL 22 2014 THE MODELS ARE IN ONLY FAIR AGREEMENT ALOFT THROUGH THE EXTENDED PORTION OF THE FORECAST. WHILE THEY ALL DEPICT THE ABNORMAL PATTERN OF A STRONG FOUR CORNERS REGION RIDGE AND DEEP TROUGHING IN THE EAST CONTINUING THROUGH THE END OF THE WEEK AND INTO THE START OF THE NEXT WEEK...THEY DIFFER ON THE MAGNITUDE AND TIMING OF THE EVOLVING EASTERN TROUGH...PARTICULARLY OVER THE WEEKEND AND INTO MONDAY. SPECIFICALLY...FALLING HEIGHTS OVER KENTUCKY WILL BE THE RULE INTO THURSDAY NIGHT AS THE RETROGRADING LOW TO THE SOUTH PULLS AWAY AND THE NORTHERN STREAM SENDS A SERIES OF SHORTWAVES THROUGH THE AREA IN NORTHWEST FLOW. THIS EASTERN TROUGH PULLS AWAY TO START THE WEEKEND WITH HEIGHTS CLIMBING TEMPORARILY BEFORE THEY FALL AGAIN IN THE FACE OF A NODE OF THE LARGE NORTHEAST TROUGH GEARING UP FOR A DIVE INTO THE UPPER MIDWEST AND OHIO VALLEY. THE 00Z GFS IS MOST AGGRESSIVE WITH THIS EVOLUTION WHILE THE 12 ECMWF KEEPS ITS CORE WAVE FURTHER TO THE NORTHWEST AND LAGS THE GFS DEVELOPMENT. HOWEVER...THE LATEST CMC AND ECMWF ARE TRENDING MORE TOWARD THE GFS. REGARDLESS... NORTHWEST FLOW WILL DOMINATE THE LOCAL PATTERN AS HEIGHTS FALL INTO MONDAY MORNING. EVENTUALLY...THE ECMWF CATCHES UP...WITH THE DEEPER AND MORE WESTERN TROUGH IDEA OF THE GFS BUT SOME SIGNIFICANT DIFFERENCES REMAIN WITH THE PATTERN OVER THE OHIO VALLEY TO CLOSE OUT THE WEEK. THE BETTER AGREEMENT EARLIER IN THE EXTENDED SUPPORTS A BLENDED SOLUTION WHILE THE LARGER SPREAD LATER ON LOWERS CONFIDENCE SO THAT THE ENSEMBLES AND A SLIGHT LEAN TOWARD THE GFS ARE PREFERRED SOLUTIONS. SENSIBLE WEATHER WILL FEATURE AN APPROACHING COLD FRONT SERVING AS A FOCUSING MECHANISM FOR SHOWERS AND THUNDERSTORMS WEDNESDAY NIGHT INTO THURSDAY. COOLER AND DRIER AIR WILL FILTER INTO THIS PART OF THE STATE LATER IN THE DAY THURSDAY PUTTING AN END TO THE CONVECTIVE CHANCES FROM NORTHWEST TO SOUTHEAST. DRY AND RELATIVELY COOL WEATHER FOLLOWS INTO THE START OF THE WEEKEND THANKS TO A BRIEF VISIT OF HIGH PRESSURE. HOWEVER...THE COLD FRONT THAT BROUGHT THE DRIER WEATHER WILL START TO SURGE NORTH OVER THE WESTERN PARTS OF THE REGION AND BRING WARMTH...MOISTURE...AND BETTER CONVECTIVE CHANCES BACK INTO THE AREA ON SATURDAY. A SERIES OF SHORT WAVES AT MID LEVELS...THE DEVELOPING TROUGH...AND THE SFC FRONTAL STRUCTURE OVER THE OHIO VALLEY KEEP SHOWER AND THUNDERSTORM CHANCES GOING INTO SUNDAY AND MONDAY. THE CR GRID LOAD PROVIDED A DECENT START TO THE FORECAST FOR THE EXTENDED...THOUGH DID ADJUST THE POPS TO ADD A TINGE OF DIURNAL TO THE TIMING OF THE CONVECTION. ALSO...TWEAKED THE LOW TEMPERATURE GRIDS A TAD TO REFLECT RIDGE AND VALLEY DIFFERENCES WEDNESDAY AND THURSDAY NIGHT. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT) ISSUED AT 139 AM EDT WED JUL 23 2014 SKIES ARE CLEARING OUT ACROSS THE AREA AND WITH SOUTHWESTERLY FLOW BRINGING IN MOIST AIR...SOME FOG WILL DEVELOP IN THE MORNING HOURS. TAF SITES SHOULD GO DOWN TO AT LEAST MVFR IF NOT SOME IFR TOWARDS DAWN. JKL IS MORE LIKELY TO SOME VALLEY FOG ADVECTED IN ON STATION. HEADING INTO THE DAY...CLOUD COVER WILL BE ON THE INCREASE AS A COLD FRONT MOVES THROUGH. HAVE PUT THUNDER IN THE TAF SITES AND ON STATION BY 19Z AS THE BEST CHANCE FOR THUNDERSTORMS WILL BE DURING THE AFTERNOON TOWARDS THE EVENING WITH THE FRONT APPROACHING AS WELL. MOST LOCATIONS SHOULD GO DOWN TO IFR CONDITIONS WITH THIS DURATION OF PRECIP. CEILINGS SHOULD THEN BE IFR THROUGH THE REST OF THE TAF PERIOD AS WELL. WINDS SHOULD BR LIGHT BUT INCREASE OUT OF THE WEST WITH THE FRONT. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...JP LONG TERM...GREIF AVIATION...SHALLENBERGER

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