Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 221800 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 200 PM EDT FRI AUG 22 2014 .UPDATE... ISSUED AT 140 PM EDT FRI AUG 22 2014 STORMS ARE STARTING TO POP OVER WESTERN WEST VIRGINIA IN ADDITION TO HINTS THAT SOME ARE STARTING TO FORM ALONG A WELL DEFINED OUTFLOW BOUNDARY DRIFTING SOUTH THROUGH CENTRAL AND PARTS OF EASTERN KENTUCKY. THE RAP MODEL IS STILL ON TRACK WITH EXPECTED DEVELOPMENTS OVER NORTHEASTERN PARTS OF THE AREA BUILDING SOUTH WITH TIME. HAVE MADE ONLY MINOR ADJUSTMENTS TO THE EXISTING FORECAST...PRIMARILY TO FINE TUNE POPS AND SKY COVER OVER THE NEXT FEW HOURS...IN ADDITION TO TWEAKING TEMPS AND DEWPOINTS PER THE LATEST OBS AND TRENDS. THESE FRESHENED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATE ISSUED AT 1200 PM EDT FRI AUG 22 2014 15Z SFC ANALYSIS SHOWS WEAK HIGH PRESSURE THROUGH THE DEEP SOUTH WITH GENERAL LOW PRESSURE TO THE NORTH AND WEST OF THIS AREA. THIS PLACES EAST KENTUCKY ON THE NORTHERN FRINGE OF THE SFC RIDGE AND ALSO THE NORTHEAST EDGE OF THE MID LEVEL ONE PARKED TO THE SOUTHWEST OF THE AREA. THE STORM TRACK...LIKE THOSE PAST COUPLE OF DAYS...IS PRETTY CLEAR AS CONVECTIVE CLUSTERS DEVELOP IN NORTHERN ILLINOIS AND INDIANA...ROLLING SOUTHEAST INTO OHIO BEFORE HITTING THE APPALACHIANS AT WEST VIRGINIA. THE BEST INSTABILITY REMAINS TO THE SOUTH AND WEST OF THIS TRACK...LEADING TO A TENDENCY FOR THESE SYSTEMS TO ARC TO THE SOUTH INTO EASTERN KENTUCKY OR KICKING OFF OUTFLOW BOUNDARIES STRONG ENOUGH TO INITIATE NEW DEVELOPMENT. THE LATEST HIGH RESOLUTION NEAR TERM MODELS INCLUDING THE HRRR AND 12Z NAM12 SUGGEST THAT BOTH SCENARIOS ARE POSSIBLE THIS AFTERNOON WITH THE FORMER FOCUSING ON SCATTERED DEVELOPMENT THROUGH THE CWA AFTER 18Z AND PERHAPS A MORE ORGANIZED SYSTEM ARRIVING FROM THE NORTHWEST AFTER 21Z. THE NAM12 FOCUSES ON THE NORTHWEST SYSTEM AND HAS IT PUSH INTO EAST KENTUCKY BETWEEN 18 AND 21Z WITH LESS AIR MASS CONVECTION AHEAD OF IT. ALOFT...THE GENESIS WAVE APPEARS TO PASS THROUGH THE SOUTHERN OHIO VALLEY BY 21Z SO THE NAM12 WITH ITS EARLIER ARRIVAL APPEARS TO BE REASONABLE. HIGH PWS AGAIN TODAY ALONG WITH GOOD INSTABILITY SUGGEST THE POTENTIAL FOR FLASH FLOODING...ESPECIALLY FOR PLACES THAT SEE TRAINING...ALONG WITH STRONG TO MARGINALLY SEVERE STORMS WITH DAMAGING WIND GUSTS AS THE MAIN THREAT. HAVE UPDATED TO CONVEY THIS IN THE SKY...POP...QPF...AND WX GRIDS. EAST KENTUCKY WILL ALSO HAVE A CONTINUANCE OF THE HOT AND HUMID CONDITIONS WITH HIGHS AROUND 90...SUBJECT TO THUNDERSTORM INDUCED COOL DOWNS...AND DEWPOINTS IN THE STEAMY LOW TO MID 70S. A NEW SET OF ZONES WERE ISSUED TO REFLECT THE ABOVE AND THE UPDATED GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATE ISSUED AT 810 AM EDT FRI AUG 22 2014 THE FORECAST REMAINS ON TRACK THIS MORNING. SHOWERS AND THUNDERSTORMS WILL LIKELY STEER CLEAR OF THE AREA UNTIL MAINLY THIS AFTERNOON. FRESHENED UP THE SKY COVER AND HOURLY TEMPERATURES AND DEW POINTS TO ALIGN BETTER WITH THE LATEST TRENDS IN OBSERVATIONS. && .SHORT TERM...(TODAY THROUGH SATURDAY) ISSUED AT 400 AM EDT FRI AUG 22 2014 THE LATEST SURFACE MAP FEATURES SURFACE HIGH PRESSURE ACROSS THE GULF COAST STATES...WITH BROADENING LOW PRESSURE ACROSS THE PLAINS. A STATIONARY FRONTAL BOUNDARY EXTENDS EAST FROM THE PLAINS INTO THE GREAT LAKES/OHIO VALLEY. ALOFT...AN UPPER LEVEL RIDGE IS CURRENTLY CENTERED NEAR LOUISIANA WITH ITS INFLUENCE EXTENDING FURTHER NORTH INTO THE MISSISSIPPI VALLEY. TROUGHING REMAINS POISED ACROSS THE WESTERN CONUS. THUNDERSTORM COMPLEXES CONTINUE TO GEN UP ON THE NORTHERN PERIPHERY OF THE RIDGE AXIS AND THEN PROCEED TO ADVANCE ESE ACROSS THE OHIO VALLEY. CURRENTLY...A WEAKENING COMPLEX IS SKIRTING NORTHEASTERN KENTUCKY...LIKELY CLEARING OUR FORECAST AREA IN THE NEXT 2 TO 3 HOURS. THE MODELS REMAIN IN GOOD AGREEMENT THROUGH THE SHORT TERM...WITH THE UPPER LEVEL RIDGE GRADUALLY AMPLIFYING ACROSS THE MISSISSIPPI VALLEY. DETAILS ASSOCIATED WITH CONVECTIVE INITIATION CONTINUE TO BE PROBLEMATIC HOWEVER...AND HAVE STUCK WITH A GENERAL MODEL BLEND...WHICH FAVORS MORE VIGOROUS CONVECTION DURING THE WARMER PART OF THE DAY. TODAY LOOKS TO BE SOMEWHAT OF A REPEAT OF YESTERDAY...WITH STOUT INSTABILITY BUILDING BY EARLY THIS AFTERNOON. WHILE THE MCS TRACK HAS SHIFTED A BIT FURTHER NORTHEAST TODAY COMPARED TO YESTERDAY...OUTFLOW BOUNDARIES CONTINUE TO BE THE MAIN PLAYER...LEAVING MOST LOCATIONS IN THE LINE OF FIRE AT SOME POINT. SOME SEVERE THUNDERSTORMS CAN NOT BE RULED OUT ONCE AGAIN TODAY...ALONG WITH ISOLATED FLASH FLOODING...WHERE STORMS CAN ALIGN ALONG OUTFLOW BOUNDARIES PARALLEL TO THE STEERING FLOW. ANOTHER HOT AND HUMID DAY LOOKS TO BE ON TAP...WITH A FEW SPOTS NEARING THE 100 DEGREE MARK IN HEAT INDICES. STORMS WILL GRADUALLY WEAKEN INTO THE EVENING HOURS...ALTHOUGH SOME NOCTURNAL ACTIVITY REMAINS AT LEAST SOMEWHAT OF A POSSIBILITY. LOWS WILL BE MUGGY ONCE AGAIN AROUND THE 70 DEGREE MARK. SATURDAY WILL FEATURE ANOTHER WARM AND HUMID DAY...ALONG WITH THE THREAT OF MORE SCATTERED CONVECTION ACROSS THE AREA. THERE WILL BE LESS INSTABILITY AVAILABLE AS MID-LEVEL WARMING TAKES PLACE FROM THE INFLUENCE OF THE UPPER RIDGE. THIS WILL KEEP THE SEVERE AND FLASH FLOOD THREAT LOWER. .LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY) ISSUED AT 400 AM EDT FRI AUG 22 2014 UPPER LEVEL RIDGING WILL REMAIN IN PLAY DURING THE DURATION OF THE EXTENDED...WITH HEIGHTS EXPECTED TO BUILD AS THE HIGH SHIFTS NEWARD ACROSS THE OHIO RIVER VALLEY. BUILDING HEIGHTS WILL THEN TRANSLATE TO RISING TEMPERATURES. HOWEVER...MID AND UPPER LEVEL WINDS WILL GENERALLY REMAIN OUT OF THE NORTH DURING THE FIRST FEW DAYS OF THE EXTENDED. THIS...COUPLED WITH CLOUD COVER THAT WILL HAMPER MAXIMUM SOLAR RADIATION...WILL KEEP HIGHS IN THE MID AND UPPER 80S THROUGH TUESDAY. TEMPS MAY THEN COOL DOWN A COUPLE DEGREES AFTER TUESDAY AS HIGH PRESSURE SITS OVERHEAD AND UPPER LEVEL HEIGHTS ASSOCIATED WITH THE RIDGE BECOME MORE STATIC. BASED ON THE LATEST FORECAST SOUNDINGS...WILL AGREE WITH PREVIOUS FORECAST THAT EACH DAY SHOULD POSE A SHOWER/THUNDERSTORM THREAT MAINLY IN THE AFTERNOON AND EVENING. GIVEN THE MID LEVEL DRYING FROM MONDAY ON...WOULDN/T BE SURPRISED IF SOME OF THESE STORMS PRODUCE SOME POTENTIAL HAIL. IN PROMISING NEWS...WITH THE RIDGING PATTERN IN PLACE...WE WILL EXPERIENCE NO BOUNDARY FORCING UNTIL VERY LATE IN THE FORECAST...SO THIS WILL HAMPER SOME OF THE BEST INSTABILITY AND WIDESPREAD INITIATION. WINDS WILL BE LIGHT AT THE SURFACE...AND REMAIN SO AS WE HEAD UP HIGHER INTO THE ATMOSPHERE. THAT BEING SAID...AFTERNOON CAPE VALUES WILL BE ABOVE THE 2K J/KG RANGE THROUGH MUCH OF THE EXTENDED...AND LAPSE RATES WILL RISE SLIGHTLY BY TUES/WED TO 6 TO 6.5 C/KM...SO AFTERNOON HEATING AND INSTABILITY MAY BE ALL THAT IS NECESSARY FOR SCATTERED CELL DEVELOPMENT EACH DAY. A BOUNDARY WILL FINALLY PUSH INTO THE AREA BY THURS/FRI DAY 7/8 /PER THE LATEST GFS MODEL RUN/. THIS WILL BRING A MORE WIDESPREAD CHANCE FOR RAIN AND THUNDERSTORMS ACROSS THE AREA. HOWEVER...THERE IS QUITE A BIT OF DISAGREEMENT IN THE EXTENDED MODELS THIS FAR OUT...SO DECIDED TO LEAN ON THE ALLBLEND FOR POPS AT THIS TIME. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON) ISSUED AT 200 PM EDT FRI AUG 22 2014 STILL AWAITING DEVELOPMENT OF STORMS THROUGH EAST KENTUCKY THIS AFTERNOON. WITHOUT A CLEAR INDICATION OF WHERE THEY WILL BE POPPING AND AFFECTING THE TAF SITES HAVE LEFT THEM WITH VCTS THROUGH THE REST OF THE DAY AND INTO THE EVENING BEFORE BACKING OFF TO JUST SOME VCSH AND LIGHT FOG LATER TONIGHT. WITH THE HIGH LEVEL OF MOISTURE OUT THERE SOME OF THE DECKS OF CLOUDS HAVE COME IN RATHER LOW FOR THE MIDDLE OF THE DAY...ESPECIALLY IN THE NORTHEAST PARTS OF THE AREA. EXPECT THIS TO BE THE CASE INTERMITTENTLY THROUGH THE FIRST PART OF THE EVENING AND ALSO WITH ANY STORM...HOWEVER...MUCH OF THE TIME AT THE SITES CIGS WILL BE VFR IF THERE AT ALL. A SIMILAR SET UP FOR TOMORROW WILL CONTINUE THE THREAT OF SHOWERS AND STORMS THROUGH THE DAY WITH A POTENTIAL FOR MVFR CIGS AND VIS WITH ANY CONVECTION. WINDS THROUGH THE PERIOD WILL BE LIGHT AND VARIABLE EXPECT DURING PEAK HEATING WHEN SOME MAINLY WESTERLY BREEZES WILL TOP OUT BETWEEN 5 AND 10 KTS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GEOGERIAN LONG TERM...JMW AVIATION...GREIF

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