Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 290817 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 417 AM EDT MON JUN 29 2015 .SHORT TERM...
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(TODAY THROUGH TUESDAY) ISSUED AT 417 AM EDT MON JUN 29 2015 HIGH AMPLITUDE PATTERN ALOFT WILL MEAN EASTERN CONUS TROUGH WILL DOMINATE OUR WEATHER THROUGH THE SHORT TERM. BAND OF SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A SFC FRONTAL SYSTEM CONTINUES TO MOVE EASTWARD ACROSS THE COMMONWEALTH THIS MORNING. MODELS...AND ESPECIALLY THE HRRR SUGGEST THAT THIS ACTIVITY WILL GRADUALLY WEAKEN AS IT MOVES INTO OUR AREA AROUND DAWN...DUE TO UPPER LEVEL SUPPORT SHEARING OUT. HOWEVER...ADDITIONAL SHORTWAVE ENERGY ALOFT ROUNDING THE BASE OF AN EASTERN CONUS TROUGH SHOULD HELP REGENERATE ACTIVITY THROUGH THE AFTERNOON. SHEAR AND INSTABILITY APPEAR SUFFICIENT FOR THE THREAT OF SOME STRONG TO SEVERE THUNDERSTORMS...MAINLY THROUGH THE AFTERNOON AND EARLY EVENING. BUT THERE ARE SOME LIMITING FACTORS FOR EXAMPLE... CLOUD COVER...LESS THAN IMPRESSIVE MID LEVEL LAPSE RATES...AND FORCING...THE STRONGEST OF WHICH MAY REMAIN FURTHER NORTH AND WEST OF OUR AREA. THEREFORE SEVERE THREAT MAY BE MORE ISOLD IN NATURE WITH RESPECT TO COVERAGE. JUST THE SAME WITH SPC PLACING OUR AREA IN A SLIGHT RISK TODAY WILL CONTINUE TO ADVERTISE THE POTENTIAL. WITH THE APPROACH OF THE SFC TROUGH TO OUR WEST AND MID LEVEL CLOUD COVER CURRENTLY MOVING INTO OUR AREA EXPECT TEMPERATURES TO BEGIN TO REBOUND ACROSS MUCH OF THE AREA BETWEEN NOW AND SUNRISE. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 351 AM EDT MON JUN 29 2015 UPPER LEVEL MODELS CONTINUE TO SUPPORT A LONGWAVE TROUGH ACROSS MUCH OF THE EASTERN CONUS TO START OFF THE PERIOD...KEEPING THE OHIO RIVER VALLEY IN NW FLOW REGIME FROM TUESDAY NIGHT THROUGH FRIDAY. THE AXIS OF THE TROUGH WILL THEN SHIFT DIRECTLY OVER KY AS ANOTHER SHORTWAVE DIGS SOUTHWARD FROM CANADA TO START OFF THE WEEKEND. FINALLY...THE UPPER LEVEL LONGWAVE PATTERN WILL SLOWLY DAMPEN AS WE HEAD INTO THE END OF THE EXTENDED PERIOD SUNDAY INTO MONDAY. HOWEVER...BY THE WEEKEND MODELS SHOW QUITE A BIT OF DISCONTINUITY...SO THE EXACT TIMING AND MAGNITUDE OF THE UPPER LEVEL TROUGH WILL BE SOMEWHAT LOW CONFIDENCE. WITH THE GENERAL NW FLOW...EXPECT SHORTWAVES TO CONTINUE TO TRAVEL SE AND INTO THE OHIO RIVER VALLEY. THIS WILL RESULT IN SEVERAL SURFACE LOW PRESSURE CENTERS AND FRONTAL BOUNDARIES PASSING THROUGH THE REGION...CREATING THE ENERGY AND LIFT TO PRODUCE SHOWERS AND THUNDERSTORMS. AS HAS BEEN THE CASE OVER THE LAST FEW WEEKS...EXPECT MOST WIDESPREAD ACTIVITY TO BE RIGHT ALONG AND JUST AHEAD OF THE FRONTAL BOUNDARY...PEAKING IN SEVERITY DURING THE AFTERNOON AND EARLY EVENING HOURS IN CONJUNCTION WITH THE PEAK HEATING. THE FIRST OF THESE BOUNDARIES WILL BE EXITING TUESDAY NIGHT AS THE NEXT BOUNDARY TO OUR NORTH MAKES A SHIFT SOUTHWARD. THIS SECOND BOUNDARY IS EXPECTED TO MAKE IT INTO THE REGION WEDNESDAY NIGHT...AND ACCORDING TO THE LATEST 00Z RUN OF THE GFS40...SHOULD BECOME STALLED OUT ACROSS THE REGION THROUGH THE DAY FRIDAY AS THE UPPER LEVEL TROUGH BACK-BUILDS ACROSS THE OHIO RIVER VALLEY. ALONG THIS BOUNDARY...EXPECT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS...WITH ANY UPPER LEVEL WAVES OF ENERGY ENHANCING CHANCES FOR A MCS TO PASS THROUGH THE REGION. THE FRONTAL BOUNDARY WILL FINALLY SHIFT SE OF THE STATE BY FRIDAY EVENING...ASSUMING MODEL TIMING PANS OUT. UNFORTUNATELY...ANOTHER WEAK FRONTAL BOUNDARY WILL HAVE FORMED TO OUR NORTH...AND WE WILL STILL BE IN VERY CLOSE PROXIMITY TO THE EXITING FRONT. UNDER SW FLOW BY THIS POINT...AND STILL IN AN UPPER LEVEL LOW PRESSURE TROUGHING PATTERN...EXPECT LESS ORGANIZED SCATTERED CONVECTION TO CONTINUE INTO THE WEEKEND...WITH BEST CHANCES STILL EXPECTED OVER THE SE CWA CLOSER TO THE EXITING FRONT. BY SUNDAY...MODEL CONFIDENCE IN CONVECTION STARTS TO DECLINE AS THERE IS LITTLE AGREEMENT IN THE PATTERN ALOFT. IF THE GFS IS CORRECT...THE UPPER LEVEL TROUGH WILL BEGIN DAMPENING/WEAKENING... BUT CONTINUED WARM SW FLOW AND A PASSING SHORTWAVE COULD BE THE SPARK FOR YET MORE SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON/EVENING HOURS. BOTH THE ECMWF AND THE GFS DO SUPPORT A LARGE UPPER LEVEL CLOSED LOW PUSHING SOUTH FROM NW CANADA TO CENTRAL CANADA BY LATE IN THE WEEKEND. THIS ENERGY WILL TRANSLATE TO THE SURFACE WITH A STRONG LOW PRESSURE SYSTEM DEVELOPING ACROSS SOUTHCENTRAL CANADA...PULLING A STRONG FRONTAL BOUNDARY WHICH WILL SWEEP ACROSS MUCH OF THE CENTRAL AND EVENTUALLY EASTERN CONUS. EXACT TIMING IS STILL OBVIOUSLY IN LOW CONFIDENCE...BUT IF THIS PANS OUT ANOTHER GOOD CHANCE OF WIDESPREAD SHOWERS AND THUNDERSTORMS WILL IMPACT THE REGION AHEAD OF THE FRONTAL ZONE AS WE END THE EXTENDED PERIOD MONDAY. WITH A NW FLOW REGIME...COOLER AIR WILL BE PULLED IN FROM CANADA TO START OUT THE EXTENDED PERIOD. THEN AS THE TROUGH BACK-BUILDS AND GENERALLY SW FLOW TAKES HOLD DURING A PORTION OF THE PERIOD...WE WILL ACTUALLY CONTINUE TO PULL COOLER AIR IN FROM THE NORTH...AS WINDS BECOME MORE NW JUST TO OUR WEST. THIS...IN CONJUNCTION WITH CLOUD COVER AND POTENTIAL RAIN...WILL KEEP TEMPERATURES MODERATED THROUGH MUCH OF THE EXTENDED...AT LEAST INTO THE WEEKEND. EXPECT HIGHS IN THE UPPER 70S TO LOW 80S. BY MONDAY...ENERGY WILL BE REDIRECTED TOWARDS THE INCOMING UPPER LEVEL HIGH...CAUSING A BREAK IN THE UPPER LEVEL WIND FLOW ACROSS THE REGION. THIS WILL ALLOW FOR A BETTER PULL OF TRUE SW WIND FLOW IN THE MID AND LOW LEVELS...WHICH COMBINED WITH ANY SUNSHINE...WILL BOOST TEMPS BACK UP INTO THE MID AND MAYBE EVEN UPPER 80S FOR THE DAY. WITH PARTLY TO MOSTLY CLOUDY SKIES EXPECTED TO STICK AROUND DURING THE NIGHT...EXPECT TEMPERATURES TO REMAIN MODERATED AS WELL...STAYING AROUND THE MID AND UPPER 60S FOR EARLY MORNING LOWS.
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&& .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 215 AM EDT MON JUN 29 2015 IN GENERAL EXPECTING VFR CONDITIONS THROUGH THE FORECAST PERIOD. AN AREA OF SCATTERED SHOWERS ASSOCIATED WITH AN APPROACHING COLD FRONTAL SYSTEM WILL OVERSPREAD THE REGION FROM WEST TO EAST AROUND DAWN THIS MORNING. SCATTERED THUNDERSTORMS ARE THEN EXPECTED TO REDEVELOP DURING THE AFTERNOON. THE PRECIPITATION MAY BRING TEMPORARY LOCALIZED IFR CONDITIONS...ESPECIALLY IN AFTERNOON THUNDERSTORMS. SOME OF THE THUNDERSTORMS MAY CONTAIN MARGINALLY LARGE HAIL AND STRONG WINDS. OTHERWISE...LIGHT SOUTHERLY WINDS WILL GRADUALLY VEER TO THE SOUTHWEST AND INCREASE TO AROUND 10 KTS...WITH HIGHER GUSTS TO AROUND 20 KTS IN THE AFTERNOON. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...RAY LONG TERM...JMW AVIATION...HAL/RAY

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