Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 290754 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 354 AM EDT WED JUL 29 2015 .UPDATE... ISSUED AT 1043 PM EDT TUE JUL 28 2015 CONVECTION IS DWINDLING...WITH ONLY A FEW SHOWERS LEFT IN THE SOUTHWEST. FORCING WILL BE LACKING OVERNIGHT...AND GIVEN THE WEAKENING TREND...DO NOT SEE MUCH REASON TO HANG ONTO TO EVEN ISOLATED POPS AT THIS POINT. BESIDES SOME PASSING HIGHER CLOUDS FROM THE NORTH...PARTLY CLOUDY TO MOSTLY CLEAR SKIES WILL RULE. HAVE THEREFORE HIT THE FOG A BIT HARDER. UPDATES HAVE BEEN SENT. UPDATE ISSUED AT 806 PM EDT TUE JUL 28 2015 MOST CONVECTION EAST OF I-75 HAS WANED...BESIDES A FEW STRAY LIGHT RETURNS AT TIMES. THE BEST COVERAGE IS CURRENTLY ALIGNED WEST OF I-75...ASSOCIATED WITH SOME WEAK LOW LEVEL CONVERGENCE AND A FAIRLY UNTAPPED ENVIRONMENT. THE HIGHER RESOLUTION SHORT TERM MODELS SHOW THIS AREA OF CONVERGENCE WEAKENING AFTER 01Z...SO HAVE CONTINUED TO ALIGN THE BEST POPS OVER THE SOUTHWEST FOR THE NEXT HOUR OR SO...BEFORE DWINDLING. WILL HANG ONTO SLIGHT POPS ELSEWHERE THROUGH AROUND MIDNIGHT...BEFORE GOING DRY. LOW TEMPERATURES AROUND 70 AND PLENTY OF FOG LOOK ON TRACK OVERNIGHT. UPDATES HAVE BEEN SENT. && .SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT) ISSUED AT 359 PM EDT TUE JUL 28 2015 CURRENT CONDITIONS ACROSS EASTERN KENTUCKY FEATURE SHOWERS AND THUNDERSTORMS ACROSS THE AREA SLOWLY SHIFTING OFF TO THE SOUTHEAST AS THEY DEVELOP. THE MAIN CONCERN THIS AFTERNOON BEING THE HEAVY RAINFALL POTENTIAL WITH PWATS IN THE 1.8 TO 2.2 RANGE AND PLENTY OF INSTABILITY. THIS HAS BEEN OCCURRING WITH A WEAK DISTURBANCE OVERHEAD WITH A FADED SURFACE BOUNDARY STRETCHING ACROSS THE AREA. DUE TO THE SATURATED AIR MASS IN PLACE AND INSTABILITY IN PLACE...WILL GO WITH CHANCE POPS WELL INTO THE EVENING TONIGHT AS PERSISTENCE WOULD ALSO SUGGEST THIS. WILL CONTINUE WITH THE MENTION OF HEAVY RAINFALL POSSIBLE IN THE HWO. THIS HAS ALSO TEMPERED THE HIGH TEMPERATURES THIS AFTERNOON. HEADING INTO TONIGHT...LINGERING CONVECTION IS EXPECTED TO CONTINUE INTO THE FIRST PART OF TONIGHT...ESPECIALLY WITH THIS SATURATED AIR MASS IN PLACE. WITH THIS INSTABILITY WILL BE SLOW TO WANE ALONG WITH PWATS STILL IN THE 2 INCH RANGE. A BRIEF BREAK IN PRECIP AND CLOUD COVER WILL LEAD TO FOG DEVELOPMENT LATE TONIGHT AND WITH DEW POINTS REMAINING IN THE LOWER 70S WITH SOME MID 70S...FOG WILL BE DENSE IN SOME AREAS. MOIST SOUTHERLY FLOW IS EXPECTED TO CONTINUE AND REMAIN PRONOUNCED WITH A BETTER DEFINED FEATURE ON THE WAY IN THE FORM OF A COLD FRONT. THIS WILL PROVIDE ENOUGH LIFT FOR CONTINUED SHOWER AND THUNDERSTORM DEVELOPMENT INTO THE AFTERNOON ON WEDNESDAY. IN FACT...INTO WEDNESDAY NIGHT...PWAT VALUES JUMP BEYOND THE 2 INCH RANGE WITH MODEL PROFILES SATURATED TO NEARLY 500MB IN MOST LOCATIONS. FOR THIS...HAVE PUT LIKELY POPS WEDNESDAY EVENING THROUGH WEDNESDAY NIGHT. SPC HAS ALSO MENTIONED A MARGINAL WIND THREAT WITH THIS ACTIVITY ALONG THE FRONT BUT THE MAIN IMPACT WILL AGAIN BE SLOW STORM MOTION WITH HEAVY RAINFALL POSSIBLY CAUSING SOME MINOR FLOODING ISSUES. IN ADDITION TO THE HEAVY RAINFALL...TEMPERATURES WILL REACH TO AROUND 90 ON WEDNESDAY AFTERNOON WITH HEAT INDEX VALUES REACHING AROUND 100 POSSIBLE IN SOME AREAS ADDING ANOTHER IMPACT TO BE MINDFUL OF. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 354 AM EDT WED JUL 29 2015 WE WILL BE IN A POST FRONTAL REGIME TO START OFF THE EXTENDED FORECAST AT 0Z FRIDAY. SURFACE HIGH PRESSURE WILL CONTINUE TO TAKE HOLD THROUGH THE DAY FRIDAY WITH SLIGHTLY COOLER NRLY WINDS AT THE SURFACE. MEANWHILE...A STRONG UPPER LEVEL LOW WILL BECOME NEARLY STATIONARY ACROSS HUDSON BAY...ROTATING AROUND THE BAY FROM FRIDAY THROUGH AT LEAST MONDAY. THIS WILL KEEP A LONGWAVE TROUGHING PATTERN ACROSS MUCH OF THE MIDWEST AND EASTERN CONUS...CONTINUING THE NW FLOW REGIME ACROSS THE OHIO RIVER VALLEY. THIS NW FLOW WILL PROVIDE THE PERFECT SCENARIO FOR SHORTWAVES TO TRACK SE ALONG THE TROUGH AND INTO THE OHIO VALLEY AS IT ROUNDS THE BASE OF THE TROUGH. HOWEVER...HIGH PRESSURE WILL HAVE HOLD AT THE SURFACE. THE QUESTION THROUGHOUT THE EXTENDED IS WHETHER OR NOT THIS HIGH PRESSURE WILL BE STRONG ENOUGH TO SWAY THE IMPACT OF THESE SHORTWAVES AS THEY MOVE THROUGH EASTERN KY. THE FIRST OF THESE SHORTWAVES WILL MOVE THROUGH SATURDAY INTO SUNDAY. AS OF 0Z FRIDAY...THE ACCOMPANYING SURFACE COLD FRONT IS POSED TO BE LOCATED ACROSS THE NORTHERN PLAINS AND UPPER GREAT LAKES REGION...AND WILL SHIFT SOUTHWARD THROUGHOUT THE DAY FRIDAY AS THE SHORTWAVE NEARS. HOWEVER...THIS BOUNDARY WILL BE MOISTURE DEPRIVED AND FAIRLY WEAK. LATEST MODELS ARE STILL SHOWING SOME DISAGREEMENT ON IF THIS BOUNDARY WILL BE ABLE TO SUSTAIN PRECIPITAL MOISTURE AS IT MOVES INTO THE OHIO RIVER VALLEY. JUST LIKE YESTERDAY...THE GFS IS POINTING TOWARDS A FEW SCATTERED SHOWERS MAKING IT INTO THE CWA...WHILE THE ECMWF IS KEEPING US DRY. MEANWHILE...DESPITE THE PLAN VIEW GFS OUTPUT...THE GFS FORECAST SOUNDINGS ARE ONLY POINTING AT A NARROW WINDOW OF MID LEVEL MOISTURE WITH ABUNDANT DRY AIR NEAR THE SURFACE. THIS IS MORE CHARACTERISTIC OF SOME SCT TO BKN CLOUD COVER RATHER THAN RAINFALL. AS SUCH...WILL CONTINUE TO TREND TOWARD THE DRIER ECMWF. THE NEXT SHORTWAVE AND SURFACE BOUNDARY WILL MOVE THROUGH TUESDAY INTO WEDNESDAY AS WE FINISH OUT THE 7 DAY FORECAST. GRANTED...THIS IS FAR OUT IN THE FORECAST...BUT MODELS ARE IN SURPRISINGLY GOOD AGREEMENT IN THE UPPER LEVELS...SO CONFIDENCE IS A BIT HIGHER. THIS PARTICULAR UPPER LEVEL SHORTWAVE WILL SHOW SIGNIFICANT DIGGING AS IT NEARS THE OHIO VALLEY REGION...LENDING TO A STRONGER SURFACE BOUNDARY. IF THIS PROVES TO BE TRUE...WE MAY SEE OUR NEXT BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS DURING THIS TIME. AS FOR TEMPERATURES... THE POST FRONTAL CONDITIONS AND DRIER NW FLOW WILL BRING IN SLIGHTLY COOLER TEMPERATURES TO START OFF FRIDAY. HOWEVER...STRONG SURFACE HIGH PRESSURE IN PLACE AND CLEAR SKIES WILL PROMOTE MAXIMUM DAYTIME RADIATION...SO THE TEMP DROP WILL NOT BE THAT GREAT...STILL MAINTAINING LOW TO MID 80S. PERHAPS MORE NOTICEABLE THAN THE SLIGHT CHANGE IN TEMPERATURES WILL BE THE DECREASE IN HUMIDITY...AS LIGHT WINDS AT THE SURFACE AND NW FLOW ALOFT WILL PROMOTE LOWER RH VALUES. AS HIGH PRESSURE REMAINS IN PLACE THROUGH MUCH OF THE EXTENDED...EXPECT TEMPS TO GRADUALLY WARM A DEGREE OR TWO EACH DAY...STAYING IN THE MID 80S THROUGH THE WEEKEND AND INTO NEXT WEEK. MEANWHILE...MAXIMUM RADIATIONAL COOLING DURING THE OVERNIGHT WILL KEEP OVERNIGHT LOWS IN THE LOW TO MID 60S THROUGH THE BEGINNING OF NEXT WEEK. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT) ISSUED AT 209 AM EDT WED JUL 29 2015 CONDITIONS VARIED WIDELY AT THE START OF THE PERIOD. HOWEVER...THE TREND WILL BE FOR WORSENING CONDITIONS...WITH A DESCENT TO LIFR OR VLIFR EXPECTED FOR MOST PLACES BEFORE DAWN. THERE WERE STILL SOME SLOW MOVING SHOWERS OVER THE SOUTHEAST PART OF THE STATE. FORECAST SOUNDINGS SHOW A POTENTIAL FOR THEM THROUGH THE EARLY MORNING HOURS...BUT WHERE AND WHEN THEY WILL DEVELOP IS TOO UNCERTAIN TO FORECAST. FOG AND ASSOCIATED LOW CLOUDS WILL LIFT AND DISSIPATE AFTER SUNRISE...GIVING WAY TO LARGELY VFR BY LATE MORNING. HOWEVER... THE DAYTIME WARMING SHOULD ALSO LEAD TO ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORM DEVELOPMENT BY AFTERNOON. THEY WILL BRING LOCALIZED IFR. THE SHOWERS AND THUNDERSTORMS SHOULD THEN LARGELY DIMINISH IN THE EVENING WITH LOSS OF HEATING. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...SHALLENBERGER LONG TERM...JMW AVIATION...HAL

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