Area Forecast Discussion
Issued by NWS Jackson, KY

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687 FXUS63 KJKL 180230 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1030 PM EDT SUN MAY 17 2015 .UPDATE...
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ISSUED AT 1030 PM EDT SUN MAY 17 2015 THE EARLIER CLUSTER OF STORMS FELL APART AS THEY ENCOUNTERED CELLS RUNNING OUT AHEAD OF THEIR LINE AND IN THE FACE OF A WEAKENING COLD POOL. ACCORDINGLY...HAVE UPDATED THE FORECAST TO LOWER POPS THROUGH THE REST OF THE NIGHT AND FINE TUNE SKY COVER. ALSO ADJUSTED THE T AND TD GRIDS TO REFLECT THE LATEST SHORTBLEND GUIDANCE...OBS...AND TRENDS. THESE UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. FRESHENED ZONES HAVE ALSO BEEN ISSUED. UPDATE ISSUED AT 730 PM EDT SUN MAY 17 2015 23Z SFC ANALYSIS SHOWS A FAIRLY TIGHT GRADIENT OVER THE AREA BETWEEN HIGH PRESSURE TO THE SOUTHEAST AND BROAD LOW PRESSURE TO THE NORTHWEST. THE DIURNAL CYCLE BROUGHT ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS TO EAST KENTUCKY THAT HAVE NOW WANED. HOWEVER... AN ARC OF MORE ORGANIZED STORMS IS NOW MOVING EAST THROUGH CENTRAL KENTUCKY. THIS AREA HAS DEVELOPED A COLD POOL AND THIS SHOULD HELP IT HOLD TOGETHER AS IT APPROACHES THE SOUTHWEST PARTS OF THE CWA OVER THE NEXT COUPLE OF HOURS. A FEW STORMS HAVE POPPED UP AHEAD OF THESE AND MAY HELP TO BREAK UP THE LINE OR LOCALLY ENHANCE IT. THE NEAR TERM MODELS HAVE NOT CAPTURED THIS MESOSCALE FEATURE WELL AND FOR THE MOST PART DAMPEN IT OUT FAR TOO QUICK. FOR OUR FORECAST...HAVE BEEFED UP POPS ALONG THIS LINE OF STORMS...AND THE COLD POOL SHOWERS BEHIND IT...AS IT TRACKS THROUGH THE CWA BETWEEN NOW AND 04Z. THIS ENTAILED HIGHER QPF AS WELL AS GUSTIER WINDS AMID THE PASSAGE. LATER AS THE CLOUDS START TO BREAK UP IN THE WAKE OF THE STORMS AND STRATIFORM RAIN...EXPECT PATCHY FOG TO DEVELOP AND LINGER THROUGH DAWN...MAINLY IN THE VALLEYS. THE WHOLE FORECAST HAS BEEN UPDATED FOR THE NIGHT ALSO INCORPORATING THE LATEST SHORTBLEND GUIDANCE...OBS...AND TRENDS. THESE GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. ADDITIONALLY...A NEW SET OF ZONES IS FORTHCOMING.
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&& .SHORT TERM...(THIS EVENING THROUGH MONDAY NIGHT) ISSUED AT 300 PM EDT SUN MAY 17 2015 THE HRRR MODEL HAS HAD THE BEST HANDLE ON THIS AFTERNOONS SHOWER AND STORM ACTIVITY...WITH THE BULK OF CURRENT ACTIVITY OCCURRING IN OUR FAR WESTERN COUNTIES. THE NAM12 HAS BEEN KEEPING CONVECTIVE ACTIVITY MOST EXTENSIVE ACROSS OUR FAR EASTERN COUNTIES...WHICH IS THE OPPOSITE OF WHAT IS ACTUALLY HAPPENING. THEREFORE...THE HRRR SOLUTION WAS USED TO COMPOSE THE FIRST 12 HOURS OF THE SHORT TERM FORECAST...AFTER 12Z...THE CONSALL SOLUTION WAS USED FOR THE FORECAST. MORE SHOWERS AND STORMS WILL CONTINUE TO FORM WEST AND SOUTHWEST OF THE AREA THROUGH THIS EVENING...AND THIS ACTIVITY WILL SLOWLY MOVE WESTWARD INTO AND ACROSS EASTERN KENTUCKY THROUGH 0Z OR SO. AFTER THAT...ONCE THE SUN IS DOWN AND LOSS OF HEATING OCCURS...THE SHOWERS AND STORMS WILL DROP OFF IN COVERAGE PRETTY QUICKLY. AFTER HIGH RAIN CHANCES THIS AFTERNOON AND EVENING...THE OVERNIGHT HOURS ARE FORECAST TO SEE ONLY ISOLATED SHOWERS AND STORMS. SHOWERS AND STORMS WILL BE ON THE INCREASE AGAIN ON MONDAY...BEGINNING IN THE LATE MORNING HOURS...AS A COLD FRONT SLOWLY APPROACHES FROM THE WEST. THE PEAK OF ACTIVITY LOOKS TO BE DURING THE AFTERNOON AND EVENING HOURS ONCE AGAIN...DURING PEAK HEATING AND FRONTAL PASSAGE. SOME OF THE STRONGER STORMS COULD PRODUCE LOCALLY HEAVY RAINFALL AND CLOUD TO GROUND LIGHTNING. TEMPERATURES DURING THE SHORT TERM ARE STILL ON TRACK TO RUN WELL ABOVE NORMAL FOR THIS TIME OF YEAR...REMAINING IN STEP WITH CURRENT TRENDS AND A PERSISTENT SOUTHERLY FLOW PATTERN THAT HAS BEEN CONSISTENTLY PUMPING WARM MOIST AIR OFF THE GULF OF MEXICO INTO THE REGION. HIGHS ON MONDAY ARE STILL EXPECTED TO TOP OUT IN THE LOWER 80S ACROSS THE AREA...WITH OVERNIGHT LOWS TONIGHT AND TOMORROW NIGHT ONLY FALLING INTO THE LOW TO MID 60S. .LONG TERM...(TUESDAY THROUGH SUNDAY) ISSUED AT 300 PM EDT SUN MAY 17 2015 MODELS APPEAR TO BE IN GOOD AGREEMENT WITH THE MID AND UPPER LEVEL PATTERN OVER OUR REGION...BUT DIFFER MORE ON DETAILS OF SENSIBLE WEATHER WITH A SHORTWAVE DISTURBANCE LATE WEDNESDAY OR WEDNESDAY NIGHT INTO EARLY THURSDAY. IN GENERAL ZONAL FLOW WILL DOMINATE THE PATTERN UNTIL THE LAST 48 HOURS OF THE EXTENDED WHERE SHORT WAVE RIDGING WILL BUILD INTO AND ACROSS THE OHIO VALLEY IN RESPONSE TO EASTWARD MOVEMENT OF WEST COAST CUT OFF LOW. AT THE SURFACE A COOL CANADIAN AIR MASS...HIGH PRESSURE SYSTEM WILL SETTLE DOWN INTO THE HEART OF THE CONUS BEHIND AN EXITING COLD FRONT...NOSING ITS WAY INTO THE OHIO VALLEY. AS A RESULT WE CAN EXPECT DRY...PLEASANTLY COOL WEATHER FOR THE START OF THE EXTENDED. ALOFT...THE AFOREMENTIONED DISTURBANCE WILL ROUND A DEEP HUDSON BAY LOW WEDNESDAY NIGHT. WE APPEAR TO RECEIVE A GLANCING BLOW FROM THIS FEATURE AS IT TRACKS THROUGH THE GREAT LAKES REGION. A SECOND LESS IMPRESSIVE DISTURBANCE BRUSHES THE OHIO VALLEY BY LATE IN THE WEEK...DY6 FRI. THE MAIN FORECAST CHALLENGE IN THE EXTENDED WILL BE THE SHORT WAVE DISTURBANCE MOVING THROUGH THE AREA WEDNESDAY NIGHT INTO EARLY THURSDAY. THE 0Z AND 12Z ECMWF PRODUCE CONSIDERABLY MORE SENSIBLE WEATHER WITH THIS FEATURE THAN EITHER THE 0Z OR 12Z GFS. NOT SEEING MUCH IN THE WAY OF TRENDS TO HELP WITH PREFERENCE OF SOLUTIONS. THEREFORE RELIED STRONGLY ON MODEL BLENDS CONSIDERING THE MURKY DETAILS WITH SENSIBLE WEATHER. INCREASING HEIGHTS THROUGH THE END OF THE EXTENDED WILL MEAN A GRADUAL RISE IN TEMPS...INTO THE 80S BY THE END OF THE FORECAST WINDOW. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING) ISSUED AT 800 PM EDT SUN MAY 17 2015 THE MAIN CONCERN WITH THIS UPDATE TO THE TAFS REVOLVE AROUND THE DOWNSTREAM IMPACTS OF THE INBOUND ARC OF STORMS AND TRAILING RAINS HEADED FOR THE JKL CWA. HAVE TIMED THIS THROUGH THE TAF SITES WITH IFR AND MVFR VIS/CIGS ALONG WITH GUSTY WINDS AS IT PASSES... DIMINISHING WITH TIME AND DISTANCE WHILE PROGRESSING EAST. FOLLOWING THE BAND OF STORMS/RAINS...PATCHY FOG WILL BE THE NEXT CONCERN AND HAVE INCLUDED AT LEAST SOME MVFR VIS AT THE SITES THROUGH 13Z. FOR MONDAY...ANTICIPATE A SIMILAR DAY WITH CONVECTION DEVELOPING FROM THE HEATING MAKING STORMS POSSIBLE IN THE AFTERNOON. OUTSIDE OF ANY STORMS...THE WINDS WILL BE LIGHT FROM THE SOUTH TO SOUTHWEST TONIGHT BEFORE PICKING UP AT 5 TO 10 KTS BY MIDDAY MONDAY...ALONG WITH SOME GUSTS TO 15 KTS POSSIBLE IN THE AFTERNOON. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...AR LONG TERM...AR AVIATION...GREIF

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