Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 271845 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 245 PM EDT THU AUG 27 2015 .SHORT TERM...
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(THIS EVENING THROUGH FRIDAY NIGHT) ISSUED AT 245 PM EDT THU AUG 27 2015 SURFACE HIGH PRESSURE OVER THE GREAT LAKES AND OHIO VALLEY WILL CONTINUE TO SLIDE EAST. THIS WILL ALLOW A WARMING TREND TO BEGIN ON FRIDAY...ALONG WITH A GRADUAL INCREASE IN DEW POINTS. WITH THE HIGH SLIPPING EAST WE SHOULD SEE LARGER RIDGE VALLEY DIFFERENCES FOR MINIMUM TEMPERATURES TONIGHT AND FRIDAY NIGHT. THE CU AND SC THAT HAVE DEVELOPED ACROSS THE NORTHERN HALF OF THE FORECAST AREA WILL DISSIPATE THIS EVENING ALLOWING FOR A MOSTLY CLEAR NIGHT...AND WE WILL HAVE A MOSTLY SUNNY DAY ON FRIDAY. THE TYPICAL RIVER VALLEY FOG WILL FORM LATE TONIGHT AND AGAIN FRIDAY NIGHT. .LONG TERM...(SATURDAY THROUGH THURSDAY) ISSUED AT 245 PM EDT THU AUG 27 2015 MODELS CONTINUE TO SHOW SIGNIFICANTLY DIFFERENT SOLUTIONS WITH REGARD TO A SHORT WAVE ROUNDING A WESTERN CONUS RIDGE AND MOVING EASTWARD ACROSS THE UPPER MIDWEST AND OHIO VALLEY. THE 0Z ECMWF REMAINS CONSIDERABLY SLOWER AND MORE AMPLIFIED WITH THIS FEATURE AND WEAKER WITH ENERGY MOVING NORTHWARD OUT OF THE GULF OF MEXICO. PER THE ECMWF SOLUTION...THE NORTHERN STREAM DISTURBANCE ONLY JUST REACHES LAKE ONTARIO BY SUNDAY MORNING. ON THE OPPOSITE EXTREME THE 06/12Z GFS CONTINUES ITS CONSIDERABLY MORE PROGRESSIVE SOLUTION... TAKING THE BULK OF THE ENERGY ASSOCIATED WITH THE SHORT WAVE TO THE EAST THROUGH THE GREAT LAKES AND OUT INTO THE ATLANTIC BY EARLY SUNDAY. THIS ACTUALLY SEEMS TO BE A FASTER TREND THAN PREVIOUS RUNS. THE GFS TAKES WHAT IS LEFT OF THIS SHORT WAVE SYSTEM AND TENDS TO DIG/CARVE OUT A POSITIVELY TILTED TROUGH OVER THE EASTERN CONUS... WITH SOME HELP FROM SOME SOUTHERN STREAM ENERGY AS IT LIFTS NORTHWARD OUT OF THE GULF. OTHERWISE...THE EVOLUTION AND END RESULT OF THE MID AND UPPER LEVEL PATTERNS ARE QUITE SIMILAR. POSITIVELY TILTED TROUGH OVER THE EASTERN CONUS SUN-MON FILLS AS STRONG WESTERN CONUS RIDGE EVENTUALLY BUILDS ACROSS THE EASTERN HALF OF THE NATION IN A RATHER AUTHORITATIVE MANNER. FLOW ALOFT MAY EVENTUALLY EVOLVE INTO AN EASTERN CONUS REX BLOCK TYPE PATTERN BY THE END OF THE EXTENDED...ATTM SUPPORTED MORE BY THE GFS WITH ITS STRONGER TROUGHINESS OVER THE DEEP SOUTH THROUGH THE PERIOD. AT PRESENT BOTH THE ECMWF AND GFS KEEP ERIKA WELL TO OUR EAST/SOUTHEAST. HOWEVER... OCCASIONAL RUNS OF THE GFS HAVE HINTED AT THE POSSIBILITY OF ERIKA TAKING A WESTERLY TURN...ALLOWING MOISTURE TO OVERSPREAD INTO THE TN VALLEY AND COMMONWEALTH OF KENTUCKY. INTERESTINGLY...A QUICK GLANCE AT THE 12Z ECMWF HINTS AT A MORE WESTERLY TREND FOR ERIKA. WITH SUCH LOW CONFIDENCE IN THE OVERALL EVOLUTION OF THE FORECAST ANYTHING IS POSSIBLE...THOUGH BASED ON ENSEMBLE MEMBERS FEEL IT IS MORE LIKELY ERIKA WILL HAVE LITTLE IF ANY IMPACT ON OUR AREA. FOR SENSIBLE WEATHER...WILL CONTINUE TO BROAD BRUSH THE FORECAST TO ACCOUNT FOR THE DIFFERENCES/INCONSISTENCIES IN THE MID/UPPER LEVEL PATTERNS. WE APPEAR TO BE HEADING INTO A MORE SEASONABLE LATE SUMMER TIME TYPE WEATHER PATTERN. LOOK FOR THE RETURN OF HEAT AND MOISTURE THROUGH THE PERIOD ALONG WITH AN INCREASING THREAT OF MAINLY DIURNALLY DRIVEN AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS THROUGH THE FIRST HALF OF THE EXTENDED...WITH SUNDAY BEING THE MOST LIKELY WINDOW OF SEEING SOME RAINFALL. THERE HAS BEEN A TENDENCY THIS SUMMER FOR THE MODELS TO BE TOO AGGRESSIVE WITH RIDGING SCENARIOS...AND WARMTH. WITH THAT CAVEAT...IF THE CURRENTLY ADVERTISED STRONG RIDGING PANS OUT THROUGH THE LATTER HALF OF THE PERIOD IT SHOULD KEEP CONVECTION AT A MINIMUM...AND DRIVE TEMPERATURES ABOVE NORMAL LEVELS. IN GENERAL WENT WITH ISOLD ISOLD TO SCT POPS THROUGH MONDAY THEN DRY UNTIL THURSDAY...THOUGH WE MAY SEE SOME ISOLD ACTIVITY OVER THE HIGHER TERRAIN TUESDAY. TEMPERATURES WILL RETURN TO NEAR OR SLIGHTLY ABOVE NORMAL LEVELS THROUGH THE PERIOD...WITH HIGHS IN THE LOW TO MID 80S TO START AND MID TO UPPER 80S TOWARDS THE END OF THE FORECAST WINDOW. A FEW LOCATIONS MAY CLIMB TO AROUND 90 BY THE END OF THE PERIOD. EXPECT MID 60S FOR MORNING LOWS.
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&& .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON) ISSUED AT 118 PM EDT THU AUG 27 2015 HIGH PRESSURE OVER THE GREAT LAKES AND OHIO VALLEY WILL CONTINUE TO CONTROL OUR WEATHER INTO FRIDAY...WITH VFR CONDITIONS PREVAILING. SCATTERED TO BROKEN CU AND SC HAVE DEVELOPED OVER THE NORTHERN HALF OF THE FORECAST AREA EARLY THIS AFTERNOON. MOST CEILINGS ARE ABOVE 4K FEET...BUT A FEW LOCAL CEILINGS AROUND 3K FEET ARE BEING OBSERVED. ANY MVFR CEILINGS WILL LIFT TO VFR BY MID AFTERNOON. SKIES WILL CLEAR THIS EVENING...AND RIVER VALLEY FOG WILL FORM LATE TONIGHT. FOG IS NOT EXPECTED TO IMPACT THE TAF SITES. A FEW N TO NE WIND GUSTS OF 12 TO 18 KNOTS FROM CAN BE EXPECTED THIS AFTERNOON...BUT OVERALL LIGHT WINDS WILL PREVAIL THROUGH THE FORECAST PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SBH LONG TERM...RAY AVIATION...SBH

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