Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 191154 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 754 AM EDT SUN APR 19 2015 .UPDATE... ISSUED AT 740 AM EDT SUN APR 19 2015 HOURLY GRIDS HAVE BEEN FRESHENED UP BASED ON RECENT TRENDS IN OBSERVATION AS WELL AS RADAR AND SATELLITE TRENDS. THIS LED TO HOLDING OFF ANY THUNDER IN THE WEATHER GRIDS UNTIL ABOUT 14Z...OR 10 AM. UPSTREAM LITTLE IF ANY LIGHTNING HAS BEEN NOTED. OTHERWISE...RAIN SHOWERS...GENERALLY LIGHT CONTINUE TO GRADUALLY OVERSPREAD THE REGION. THIS SHOULD CONTINUE OVER THE NEXT COUPLE OF HOURS. SOME OF THE HEAVIER SHOWERS OR STRONGER RETURNS OVER THE CUMBERLAND PLATEAU OF TN SHOULD ROTATE UP ACROSS THE LAKE CUMBERLAND REGION THROUGH MID MORNING. OTHERWISE...THE POTENTIAL FOR SOME DESTABILIZATION IN THE AFTERNOON AND EVENING LEADING TO A FEW STRONG TO SEVERE THUNDERSTORMS WILL CONTINUE TO BE MONITORED. SOME OF THE HIGH RESOLUTION GUIDANCE HAS THUNDERSTORMS DEVELOPING OVER OR NEAR THE REGION AND WORKING ACROSS MAINLY WESTERN PORTIONS OF THE AREA INTO THE EVENING. HOWEVER...THIS GUIDANCE SUCH AS THE HRRR IS NOT CONSISTENT FOR RUN TO RUN WITH THE SFC LOW TRACK. ONE RUN IT IS CLOSER TO THE AREA AND HAS MORE MID AFTERNOON TO EVENING ACTIVITY...WHILE THE NEXT IS FURTHER NW WITH THE SURFACE LOW TRACKS AND KEEPS THE BULK OF THE ACTIVITY TO OUR NORTH AND WEST. THE POTENTIAL FOR THIS IS HIGHLIGHTED IN THE HWO. && .SHORT TERM...(TODAY THROUGH MONDAY) ISSUED AT 330 AM EDT SUN APR 19 2015 A CLOSED MID AND UPPER LEVEL LOW IS MOVING EAST INTO THE CENTRAL PLAINS STATES EARLY THIS MORNING WITH A TROUGH AXIS TRAILING INTO THE SOUTHERN PLAINS. AN UPPER LEVEL RIDGE AXIS EXTENDED NORTH FROM THE YUCATAN REGION NORTH INTO FL AND THEN FURTHER NORTH INTO THE GREAT LAKES REGION. FURTHER WEST ANOTHER RIDGE WAS IN PLACE OVER PARTS OF THE EASTERN PACIFIC. IN THE NORTHERN STREAM...A TROUGH WAS WORKING ACROSS THE CANADIAN PLAINS AND NEARING THE DAKOTAS. THERE WERE A FEW WEAKER SHORTWAVES MOVING WITHIN THE SOUTHWEST FLOW BETWEEN THE TROUGH AND THE RIDGING OVER THE SOUTHEASTERN STATES. IN ADVANCE OF THIS TROUGH...AND ASSOCIATED SFC LOW...MOISTURE WAS RETURNING NORTH AND NORTHEAST ACROSS THE SOUTHEASTERN STATES AND MS VALLEY REGION. AT THE SFC...PRESSURE PATTERN SOMEWHAT COMPLEX...WITH A NORTHERN STREAM COLD FRONT EXTENDING INTO THE NORTHERN PLAINS AND ROCKIES ASSOCIATED WITH THE NORTHERN STREAM SYSTEM. MEANWHILE...AN AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS. FURTHER SOUTHEAST ANOTHER AREA OF LOW PRESSURE WAS OVER THE MS VALLEY REGION...ALONG A QUASI WARM FRONT THAT EXTENDED SOUTHEAST FROM ORGANIZING LOW PRESSURE OVER THE PLAINS. AS THE TROUGH WORKS FURTHER EAST AND A LEAST ONE SHORTWAVE MOVE NORTHEAST IN THE SOUTHWEST FLOW ALOFT...THE SFC WAVE SHOULD TRACK TO OR REORGANIZE NEAR THE CONFLUENCE OF THE OH AND MS RIVERS OVER THE NEXT SEVERAL HOURS. AS THIS OCCURS...THE WARM FRONT WILL APPROACH EASTERN KY...BEFORE MOVING INTO THE AREA OVER THE UPCOMING DAY. THE SFC WAVE WILL TRACK BY TO OUR NORTHWEST...WITH THE WARM FRONT LIFTING INTO WV AND OH BY MID TO LATE EVENING. AS THE ASSOCIATED SFC LOW MOVES INTO THE GREAT LAKES...THE TRAILING COLD FRONT SHOULD APPROACH THE REGION LATE SUNDAY TONIGHT AND CROSS THE AREA ON MONDAY. OVER THE NEXT SEVERAL HOURS...AS THE WARM FRONT LIFTS NORTH ACROSS THE TN VALLEY REGION AND INTO THE LOWER OH VALLEY AND APPALACHIAN REGION...A BAND OF SHOWERS WITH SOME POSSIBLE EMBEDDED THUNDERSTORMS IS EXPECTED TO WORK NORTH FROM THE SOUTHEASTERN STATES FROM NEARER TO DAWN AND LIFT ACROSS THE AREA THIS MORNING THROUGH MID AFTERNOON. IN ADVANCE OF THIS BAND OF SHOWERS...SOME MORE ISOLATED TO SCATTERED SHOWER ACTIVITY IS EXPECTED TO CONTINUE. SOME MID LEVEL DRYING IS ANTICIPATED IN THE WARM SECTOR DURING THE LATE MORNING AND AFTERNOON OVER CENTRAL KY AND MIDDLE TN. THIS SHOULD EXTEND INTO EASTERN KY AS WELL...STARTING EARLY THIS AFTERNOON IN THE FAR SOUTHWEST AND THE GRADUALLY SPREADING NORTH AND EVENTUALLY EAST. SOME DESTABILIZATION SHOULD ALSO OCCUR DURING THE AFTERNOON TO EARLY EVENING. THIS SHOULD LEAD TO MORE SCATTERED SHOWERS AND SOME THUNDERSTORMS...ESPECIALLY ACROSS THE WESTERN HALF OR SO OF THE AREA CLOSER TO THE ACTUAL SFC LOW TRACK. INSTABILITY IS NOT EXPECTED TO BE ALL THAT HIGH...WITH CAPE SOMEWHAT LIMITED. MODEL FORECAST SOUNDINGS INDICATE SBCAPE MAY REACH THE 1000 TO 1500 J/KG RANGE WITH SOMEWHAT STRONG FLOW ALOFT. THIS COULD SUPPORT SOME STRONGER THUNDERSTORMS WITH LOCALLY HEAVY RAIN...GUSTY WINDS AND POSSIBLY HAIL. A STRAY STORM OR TWO COULD BECOME SEVERE WITH STRONG WINDS THE PRIMARY THREAT...PENDING HOW UNSTABLE OR NOT THE REGION EVENTUALLY BECOMES. SPC HAS PLACED THE ENTIRE REGION IN A MARGINAL RISK FOR SEVERE THUNDERSTORM WITH THE HIGHER RISKS REMAINING WELL SOUTH AND SOUTHWEST OF EASTERN KY. EAST OF THE SFC LOW TRACK...THERE MAY BE A EVER SO SLIGHTLY HIGHER PROBABILITY FROM MIDDLE TN NORTH INTO CENTRAL AND NORTHERN KY. WITH THE LOSS OF DAYTIME HEATING AND WEAK MID LEVEL RIDGING PROGGED TO WORK ACROSS THE REGION OVERNIGHT...THERE SHOULD BE A LULL IN SHOWER AND ANY THUNDERSTORM ACTIVITY FROM LATE EVENING THROUGH MUCH OF SUNDAY NIGHT. THE CHANCES FOR ACTIVITY SHOULD INCREASE AGAIN TOWARD DAWN AND PEAK ON MONDAY AS THE COLD FRONT WORKS ACROSS THE AREA. IF SOME HEATING CAN OCCUR ACROSS EASTERN SECTIONS OF THE AREA IN ADVANCE OF THE FRONT...A COUPLE OF STRONG TO POSSIBLY SEVERE THUNDERSTORMS WOULD BE POSSIBLE WITH STRONG WINDS BEING THE MAIN THREAT. THE PRECIPITATION CHANCES WILL BEGIN TO DECREASE FROM WEST TO EAST BY EARLY ON MONDAY EVENING. .LONG TERM...(MONDAY NIGHT THROUGH SATURDAY) ISSUED AT 334 AM EDT SUN APR 19 2015 PERIOD WILL BEGIN WITH RAIN SHOWERS MAINLY ACROSS THE SE PORTIONS...AS A COLD FRONT AND UPPER LEVEL SHORT WAVE PULL OUT OF THE REGION. HIGH PRESSURE WILL BUILD TO THE SOUTH OF THE REGION WITH COOLER AND DRIER AIR BUILDING INTO EASTERN KY. AFTER A WARM WEEKEND HIGHS ON TUESDAY WILL GENERALLY BE IN THE LOWER 60 UNDER SUNNY SKIES...WHICH WILL BE NEARLY 10 DEGREES BELOW NORMAL. THIS HIGH WILL MOVE EAST AND BRING SOME RETURN FLOW TO THE REGION TUESDAY NIGHT. HOWEVER TEMPS THROUGH THE PERIOD WILL STAY BELOW NORMAL. ALSO A WEAK FRONT AND WEAK UPPER LEVEL WAVE ROUNDING THE BASE OF THE UPPER LEVEL LOW CENTERED NEAR THE GREAT LAKES. THIS WILL BRING SLIGHT TO CHANCE POPS TUESDAY NIGHT INTO WEDNESDAY. HOWEVER THERE IS STILL SOME DIVERGENCE WITH THIS SETUP IN THE GUIDANCE...SO DID LEAN TOWARD THE BLEND MORE AT THIS POINT. THE ECMWF IS A BIT MORE INLINE WITH THE GFS THAN PREVIOUS RUNS FROM YESTERDAY...BUT REMAINS SLOWER THAN THE GFS IN THE LATEST RUNS. THE RAIN CHANCES DO WANE AS WE MOVE WEDNESDAY NIGHT INTO THURSDAY AS FRONT DROPS SOUTH OF THE REGION. THIS FRONT WILL BRING ANOTHER SHOT OF COLD AIR WITH 850 TEMPS IN THE 0 TO -4 RANGE THURSDAY NIGHT. THIS COUPLED WITH CLEARING SKIES COULD LEAD TO FROST DEVELOPMENT OVERNIGHT THURSDAY INTO FRIDAY MORNING ESPECIALLY ACROSS THE BLUEGRASS WHERE HIGH PLACEMENT IS BETTER. RIGHT NOW THE CONFIDENCE IS LOWER...SO WILL LEAVE OUT OF THE GRIDS FOR NOW. DID OPT TO LEAN TOWARD A RAW MODEL BLEND WHICH DID INTRODUCE SOME MID TO UPPER 30S ACROSS THE REGION. THIS HIGH PRESSURE IS EXPECTED MOVE EAST ACROSS THE REGION FRIDAY WITH INCREASING CLOUDS ACROSS THE CUMBERLAND VALLEY LATE FRIDAY AS NEXT SYSTEM APPROACHES. BOTH THE GFS AND ECMWF WANT TO KEEP A DEVELOPING SURFACE LOW TO THE SOUTH OF THE REGION. THIS WOULD SUPPRESS THE BETTER DYNAMICS WITH FORECAST SOUNDINGS SHOWING FAIRLY MEAGER INSTABILITY. DO INTRODUCE CHANCE POPS WITH BETTER CHANCES ACROSS THE SOUTHERN PORTIONS OF EASTERN KY. ALSO KEPT WITH PREVIOUS FORECAST IN TERMS OF NO THUNDER SATURDAY GIVEN THAT THE WARM SECTOR AND BETTER DYNAMICS WILL BE WELL SOUTH GIVEN LOW PLACEMENT. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING) ISSUED AT 750 AM EDT SUN APR 19 2015 LOW AND MID LEVELS CONTINUE TO GRADUALLY SATURATE ACROSS THE REGION...BUT AS OF 11Z...CIGS AND VIS WERE STILL VFR AT ASOS AND AWOS SITES IN EASTERN AND SOUTH CENTRAL KY. AS FURTHER SATURATION OCCURS THROUGH THE 15Z TO 16Z TIMEFRAME...THESE SHOULD LOWER FURTHER TO MVFR...EXCEPT PERHAPS A TAD LATER AT SJS. AN AREA OF SHOWERS SHOULD WORK ACROSS THE REGION THROUGH ABOUT 19Z. IF ANY OF THESE ARE HEAVY ENOUGH CIGS COULD BE REDUCED AT TIMES TO IFR...ESPECIALLY AT SME AND LOZ. THE DETERIORATION INTO MVFR SHOULD ARRIVE FIRST AT WESTERN LOCATIONS...WITH EASTERN LOCATIONS HOLDING OFF LONGER DUE TO INITIAL LOW LEVEL DOWNSLOPE FLOW OFF THE HIGH TERRAIN TO OUR SE. THUNDERSTORMS WITH GUSTY WINDS AND VIS TO IFR AND POSSIBLY BRIEFLY NEARING AIRPORT MINS WILL ALSO BE POSSIBLE...MAINLY 18Z AND LATER WEST OF INTERSTATE 75...WITH CHANCES POSSIBLY SPREADING NORTHEAST AS FAR AS SYM AND SJS BY 23Z OR SO. CHANCES FOR PRECIP SHOULD DIMINISH FROM SW TO NORTHEAST 22Z TO 3Z IN SOME DRY SLOTTING BETWEEN THE WARM FRONT AND AN APPROACHING COLD FRONT. VIS AND CIGS SHOULD RETURN TO THE VFR RANGE FOR SEVERAL HOURS IN MANY LOCATIONS DURING THE LAST 12 HOURS OF THE PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...JP LONG TERM...DJ AVIATION...JP

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