Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200757 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 357 AM EDT MON APR 20 2015 .SHORT TERM...
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(TODAY THROUGH TUESDAY) ISSUED AT 355 AM EDT MON APR 20 2015 THERE ARE TWO MAIN CONCERNS THIS FORECAST CYCLE. THE FIRST CONCERN IN THE CONVECTIVE LINE APPROACHING THE SOUTHWEST PART OF THE CWA THAT IS RUNNING OUT AHEAD OF AN APPROACHING COLD FRONT. SOME STRONG WIND GUSTS HAVE BEEN OBSERVED CLOSER TO THE I 65 CORRIDOR IN TN AND KY WITH THIS LINE. SPC MESOANALYSIS STILL INDICATED DECENT SHEAR AND SOME MARGINAL TO MODEST CAPE AHEAD OF THE LINE INTO THE LAKE CUMBERLAND REGION. THIS REGION WILL CONTINUE TO BE MONITORED FOR STRONG THUNDERSTORMS OVER THE NEXT COUPLE OF HOURS. THE REGION REMAINS IN A MARGINAL SEVERE THUNDERSTORM RISK FOR THE REST OF THE OVERNIGHT HOURS. OTHERWISE...THE REMNANTS OF THIS CONVECTION SHOULD MOVE ACROSS THE AREA WITHIN A COUPLE OF HOURS OF DAWN. THERE MAY BE A RELATIVE LULL IN ACTIVITY FOR A COUPLE OF HOURS AFTER THIS AREA PASSES...BEFORE ADDITIONAL SHOWER AND THUNDERSTORM DEVELOPMENT ALONG AND IN ADVANCE OF THE ACTUAL COLD FRONT ITSELF AND APPROACHING 500 MB TROUGH AXIS. THE STRENGTH OF THIS ACTIVITY WILL BE DETERMINED BY HOW MUCH THE EARLY DAY CONVECTION SUPPRESSES INSTABILITY AHEAD OF THE FRONT AND ANY HEATING THAT MAY BE ABLE TO OCCUR ACROSS THE CENTRAL AND EASTERN CWA. THE NAM HAS A BIT MORE WARMING AND THUS IS CONSIDERABLY MORE UNSTABLE WITH CAPE INTO THE 1000 TO 1500 J/KG RANGE DURING THE AFTERNOON WHILE THE GFS HAS MUCH LESS INSTABILITY. SPC HAS A MARGINAL RISK FOR SEVERE THUNDERSTORMS ACROSS THE EASTERN TWO THIRDS OF THE AREA FOR THE UPCOMING DAY ON MONDAY. STRONG WIND GUSTS WOULD BE THE PRIMARY THREAT FROM ANY AFTERNOON TO EARLY EVENING ACTIVITY AND HAIL WOULD ALSO BE POSSIBLE. THE THREAT FOR SHOWERS WILL WANE BEHIND THE FRONT THIS EVENING WITH SFC HIGH PRESSURE ACROSS THE SOUTHERN STATES NOSING INTO THE COMMONWEALTH OVERNIGHT AND INTO THE DAY ON TUESDAY. HOWEVER...A WEAK COLD FRONT OR SFC TROUGH IS EXPECTED TO APPROACH THE REGION LATE IN THE PERIOD...ALONG WITH A MID LEVEL SHORTWAVE. MOISTURE WITH THIS SYSTEM WILL BE RATHER LIMITED AND NOT MUCH MORE THAN AN INCREASE IN MID LEVEL CLOUDS IS EXPECTED BEFORE THE END OF THE PERIOD. A STRAY SHOWER OR SOME SPRINKLES CANNOT BE RULED OUT AT THE VERY END OF THE PERIOD NEAR THE I 64 CORRIDOR AND NORTH. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 332 AM EDT MON APR 20 2015 PERIOD WILL BEGIN WITH HIGH MOVING SOUTH OF THE REGION AND WEAK FRONTAL BOUNDARY DROPPING SOUTH ACROSS THE OHIO VALLEY. THIS WILL BRING SOME RAIN SHOWERS ACROSS PORTIONS OF THE REGION. GIVEN GUIDANCE CONTINUES TO HAVE SOME DISCREPANCIES ON EXACT TIMING...WILL STAY IN THE CHANCE TO SLIGHT AT THIS POINT. GIVEN THAT THIS FRONT IS WEAKER AND PWATS IN THE 0.50 TO 0.80 RANGE WOULD THINK QPF WILL BE GENERALLY LIGHT WITH THIS SYSTEM. DO KEEP RAIN SHOWERS AS WE MOVE INTO WEDNESDAY AND DO INTRODUCE AFTERNOON THUNDERSTORMS IN THE SOUTH NEAR THE TN/VA BORDE45R. THIS SEEMED WARRANTED GIVEN A BIT MORE INSTABILITY IN THE AFTERNOON HOURS AND FOR NOW CAPPED THIS AT SLIGHT CHANCE. CHANCES MAY NEED TO BE INCREASED IN SUBSEQUENT FORECAST RUNS DEPENDING ON HOW THIS FRONT PROGRESSES. DOES LOOK LIKE WE GET ANOTHER BREAK AS HIGH PRESSURE TRIES TO BUILD SOUTHEAST ACROSS THE REGION WEDNESDAY NIGHT INTO THURSDAY. THE FORECAST BECOMES LESS CLEAR AS WE MOVE FARTHER INTO THE LONG TERM...AS ALL EYES TURN TOWARD UPPER LEVEL SHORTWAVE EJECTING OUT OF THE DESERT SOUTHWEST. LATEST GFS MODEL RUN IS MUCH MORE PROGRESSIVE WITH THIS SYSTEM THAN THE ECMWF AND GEM. THE GFS IS ALSO STRONGER WITH THE SURFACE LOW AS IT BRINGS A LESS FLATTENED SHORTWAVE ACROSS THE TN AND OH VALLEYS. THE 00Z GFS AND 00Z GFS ENSEMBLE MEAN ARE IN DECENT AGREEMENT WITH PLACEMENT OF SURFACE LOW AND UPPER LEVEL PATTERN. HOWEVER GIVEN UNCERTAINTY WILL STICK CLOSE TO MODEL BLEND AT THIS POINT BEING THAT THIS IS DAY 5 AND 6. THIS WOULD YIELD THE BEST POPS FRIDAY NIGHT INTO SATURDAY. NOW THE FASTER GFS ALSO BRINGS TO QUESTION IF WE WILL SEE THE COLDER TEMPS FRIDAY MORNING THAT WERE PREVIOUSLY EXPECTED...SO HAVE BACKED OFF ON THIS NOTION GIVEN THAT BOTH MODELS HAVE TRENDED WARMER AT 850MB FROM PREVIOUS RUNS. HIGH TEMPS THROUGH THE PERIOD WILL GENERALLY BE AROUND 10 DEGREES BELOW NORMAL.
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&& .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 200 AM EDT MON APR 20 2015 SOME SCATTERING OUT OF THE LOW CLOUDS HAS OCCURRED AND SHOULD TRANSLATE NORTHEAST ACROSS THE AREA FOR SOME TIMES OF VFR OVER THE NEXT 3 TO 5 HOURS AT THE TAF SITES. AFTER THAT...ANOTHER ROUND OF SHOWERS AND POSSIBLY A STRAY THUNDERSTORM MAY MOVE THROUGH FROM WEST TO EAST BETWEEN ABOUT 09Z AND 14Z. A BETTER SHOT AT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL COME GENERALLY BETWEEN 18Z TO 00Z. ANY OF THE STRONGER SHOWERS OR THUNDERSTORMS WILL BE CAPABLE OF DROPPING CONDITIONS BELOW MVFR AT LEAST FOR A TIME. OTHERWISE...MAINLY VFR OR MVFR IS EXPECTED THROUGH THE PERIOD. WINDS WILL PICK UP OUT OF THE WEST AROUND 16Z AND AFTER...WITH SOME GUSTS TOPPING 20 KTS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...DJ AVIATION...JP

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