Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200725 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 325 AM EDT SAT SEP 20 2014 .UPDATE... ISSUED AT 140 AM EDT SAT SEP 20 2014 HOURLY GRIDS HAVE BEEN FRESHENED UP BASED ON RECENT OBSERVATIONS AND TRENDS. THIS LED TO SLIGHTLY COLDER MIN T IN A COUPLE OF SPOTS ACROSS THE NORTH...WITH THE MAIN CHANGE BEING MORE FOG IN THE GRIDS FOR VALLEY LOCATIONS OUTSIDE OF THE HIGHEST TERRAIN WHERE THE PRESSURE GRADIENT WAS WEAKER. WE HAVE RECEIVED A SPOTTER REPORT OF DENSE FOG NEAR THE RED RIVER IN POWELL COUNTY AND 11-3.9 SAT IMAGERY SUPPORTS VALLEY FOG AT PRESENT IN PARTS OF THE LIKING...BIG SANDY...KENTUCKY AND RED RIVER VALLEYS. SOME OF THE FOG SHOULD AGAIN BE DENSE GENERALLY ALONG THE LARGER CREEKS AND STREAMS AND ESPECIALLY RIVERS AND LARGER LAKES. THE PRESSURE GRADIENT IS EXPECTED TO RELAX A BIT OVERNIGHT ACROSS THE SOUTHEAST PART OF THE CWA SO OUTSIDE OF WHERE SOME CLOUDS DEVELOP IN THE WARM SECTOR...VALLEY FOG SHOULD ALSO DEVELOP THERE TOWARD DAWN. SOME OF THE GUIDANCE INDICATES THE POTENTIAL FOR A FEW STRAY SHOWERS AS A WEAK DISTURBANCE APPROACHES...MAINLY ACROSS THE WESTERN AND NORTHWESTERN PARTS OF THE CWA LATER TONIGHT INTO EARLY ON SATURDAY. CONFIDENCE IN THIS IS NOT ALL THAT HIGH...BUT IT DOES HAVE SUPPORT FROM THE NAM...SOME OF THE RECENT HRRR RUNS AND SOME PRIOR BUT NOT THE MOST RECENT RAP RUN. WE WILL CONTINUE TO EVALUATE THIS POTENTIAL FOR THE SCHEDULED MORNING FORECAST RELEASE. UPDATE ISSUED AT 1027 PM EDT FRI SEP 19 2014 USED OBSERVED TEMPERATURES AND DEW POINTS TO ADJUST HOURLY GRIDS FOR TONIGHT...BLENDING TOWARD THE PREEXISTING FORECAST BY MORNING. NO SUBSTANTIVE CHANGES TO THE OVERALL FORECAST WERE MADE. UPDATE ISSUED AT 729 PM EDT FRI SEP 19 2014 HAVE UPDATED TO ALLOW FOR A FASTER DROP IN VALLEY TEMPS THIS EVENING. ALSO...REDUCED SKY COVER FOR MOST AREAS THIS EVENING. MESOSCALE MODELS ARE PERSISTENT IN SHOWING CLOUDS DEVELOPING NEAR OUR WESTERN BORDER LATE TONIGHT INTO SATURDAY MORNING...A WELL AS SOME SHOWERS. HAVE ACCOUNTED FOR A FEW CLOUDS...BUT KEPT THE FORECAST IN THE JKL FORECAST AREA DRY AT THIS POINT. && .SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT) ISSUED AT 307 PM EDT FRI SEP 19 2014 A LARGE DOME OF HIGH PRESSURE WILL REMAIN ANCHORED OVER THE EAST COAST INTO THE WEEKEND...PROVIDING A DRY START TO THE WEEKEND. STILL A REMOTE CHANCE OF AN ISOLATED SHOWER ACROSS PIKE COUNTY LATER THIS EVENING...BUT CHANCES SEEM TO BE DIMINISHING WITH EVERY HOUR THAT PASSES. THE CU JUST DOES NOT LOOK ALL THAT IMPRESSIVE. REGARDLESS...UNTIL INSTABILITY WANES THIS EVENING CANNOT RULE OUT A BRIEF POP UP SHOWER. SKIES WILL CLEAR OUT AGAIN TONIGHT. WITH DEW POINTS CLIMBING HIGHER TODAY...AND CLEARING SKIES...ANOTHER NIGHT OF FOG CAN BE EXPECTED ACROSS THE AREA. SHOULD BE A FAIRLY TYPICAL FOG FOR THIS TIME OF YEAR. HIGHS WILL CLIMB TO THE HIGHEST READINGS OF THE WEEK ON SATURDAY AS TEMPERATURES CLIMB INTO THE LOW 80S DURING THE AFTERNOON. CLOUDS WILL BE ON THE INCREASE SATURDAY NIGHT AS A COLD FRONT PUSHES SOUTH INTO THE OHIO RIVER VALLEY. PRECIPITATION ASSOCIATED WITH THIS BOUNDARY COULD MAKE IT INTO AREAS NORTH OF 1-64 PRIOR TO 12Z SUNDAY...BUT IT APPEARS THE MAIN PRECIPITATION WITH THE FRONT SHOULD COME COME LATER ON SUNDAY. WITH CLOUDS AND SURFACE MOISTURE INCREASING SATURDAY NIGHT...A MILDER NIGHT IS ON TAP WITH LOWS ONLY INTO THE 60S. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 324 AM EDT SAT SEP 20 2014 A QUICK MOVING COLD FRONT WILL BE EXITING THE REGION AS OF 0Z MONDAY. MODELS CONTINUE TO COME INTO A BETTER AGREEMENT FOR THE ENDING TIME OF PRECIP ASSOCIATED WITH THE FRONT...WITH THE NW EXPECTED TO CLEAR OUT BY 0Z...AND FINALLY THE SE JUST AFTER 6Z MONDAY. LATEST FORECAST SOUNDINGS ARE STILL ONLY SUPPORTING MARGINAL INSTABILITY FOR THE PRECIP ACCOMPANYING THIS FRONT...QUICKLY DISSIPATING AS WE LOSE DAYTIME HEATING...AND ONCE THE FRONTAL BOUNDARY HAS PASSED. AS SUCH...THUNDER WAS MENTIONED IN PREVIOUS FORECAST PAST 0Z...AND HAS ALSO BEEN INCLUDED BY SURROUNDING OFFICES THROUGH THE FIRST PART OF THE EVENING. DID NOT FEEL CONFIDENT ENOUGH TO YANK MENTION OF THUNDER COMPLETELY AT 0Z...SO KEPT MENTION OF SLIGHT CHANCE THUNDER WITH CHANCE POPS THROUGH 3Z...WHICH CONSEQUENTLY IS ABOUT THE SAME TIME CHANCE POPS EXIT THE REGION ANYWAYS. THERE IS SOME CONCERN THAT THE COMBINATION OF STRONG SUBSIDENCE BEHIND THE FRONT...IN ADDITION TO THE LINGERING MOISTURE ACROSS THE REGION...WILL LEAD TO A WIDESPREAD FOG EVENT BY LATE SUNDAY NIGHT...OR PERHAPS A LOW STRATUS EVENT. THE EXTENT OF EITHER OF THESE IS STILL SOMEWHAT UNCERTAIN. DECIDED TO INCREASE CLOUDS SLIGHTLY OVERNIGHT SUNDAY NIGHT/MONDAY MORNING...BUT DID NOT MENTION FOG AT THIS TIME. AS THE FRONT QUICKLY DEPARTS SUNDAY EVENING/NIGHT...KY WILL FIND ITSELF ON THE BACKSIDE OF THE UPPER LEVEL TROUGHING PATTERN...WITH STRONG NW FLOW BRINGING MUCH COOLER CANADIAN AIR INTO THE REGION. AS HIGH PRESSURE TAKES HOLD...DRY AND SUNNY SKIES WILL PREVAIL DURING THE DAY MONDAY...BUT HIGH TEMPERATURES WILL STRUGGLE TO MAKE IT TO THE 70 DEGREE MARK. AIRMASS MODIFICATION...NAMELY THE LESSENING OF STRONG PRESSURE GRADIENT/NW FLOW AS THE UPPER LEVEL RIDGE TAKES FULL CONTROL...WILL SLOWLY ALLOW TEMPS TO RISE THROUGHOUT THE REMAINDER OF THE EXTENDED FORECAST PERIOD. HOWEVER WE LIKELY WON/T SEE TEMPS HIT ABOVE THE 80 DEGREE MARK AGAIN UNTIL AT LEAST NEXT WEEKEND. MEANWHILE...WITH SUCH STRONG SUBSIDENCE IN CONTROL...THERE WILL BE LITTLE CONCERN FOR CLOUDS...LET ALONE PRECIP CHANCES. ALL IN ALL IT LOOKS TO BE A GORGEOUS AUTUMN-LIKE WEEK AHEAD. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT) ISSUED AT 150 AM EDT SAT SEP 20 2014 ASIDE FROM VALLEY FOG DEVELOPING...AND THEN LIFTING AND DISSIPATING THROUGH 13Z TO 14Z...VFR CONDITIONS WITH LIGHT WINDS WILL PREVAIL DURING THE PERIOD. A COLD FRONT AND ASSOCIATED INCREASE IN CLOUDS IS EXPECTED LATE IN THE PERIOD. THE FOG IS AGAIN EXPECTED TO FOLLOW ITS TYPICAL LATE SUMMER/EARLY AUTUMN PATTERN OF DEVELOPING FIRST IN DEEP VALLEYS AND THEN GROWING IN BREADTH AND DEPTH...WITH THE POTENTIAL TO BEGIN TO REACH SOME RIDGES AND OPEN TERRAIN BY DAWN...SUCH AS MVFR AT SJS IF WINDS SLACKEN AND POSSIBLY MVFR AT SME WHERE THE CURRENT DEWPOINT DEPRESSION IS LOW BUT THERE ARE SCT CLOUDS AS WELL. THE LARGER RECENT OBSERVED DEWPOINT DEPRESSION OF 7 AT LOZ POINTS TOWARD ANY FOG THAT DEVELOPS BEING IN THE VFR RANGE. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...KAS LONG TERM...JMW AVIATION...JP

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