Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 181202 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 802 AM EDT SAT OCT 18 2014 .UPDATE... ISSUED AT 801 AM EDT SAT OCT 18 2014 MADE ONLY MINOR ADJUSTMENTS BASED ON LATEST OBS TRENDS AND MODEL RUNS...WITH NO SUBSTANTIVE CHANGES TO THE OVERALL FORECAST. && .SHORT TERM...(TODAY THROUGH SUNDAY) ISSUED AT 400 AM EDT SAT OCT 18 2014 A COLD FRONT PASSED THROUGH ON FRIDAY EVENING. COLD AIR ADVECTION WILL PERSIST BEHIND THE FRONT TODAY AND TONIGHT. THE CHANGE IN AIR MASS WILL STEEPEN LOW LEVEL LAPSE RATES ENOUGH THAT LOW CLOUDS WILL DEVELOP SOUTHWARD OVER THE AREA ON SATURDAY. MEANWHILE...A SHORTWAVE TROUGH WILL MOVE SOUTHEAST...APPROACHING THE REGION THIS AFTERNOON AND EVENING. THE GFS AND NAM BOTH SHOW NEARLY SATURATED FORECAST SOUNDINGS FROM AROUND 925 MB TO 650 MB LATE TODAY AND EARLY THIS EVENING OVER THE NORTHERN AND EASTERN PORTIONS OF THE FORECAST AREA...WITH THE TOP OF THE LAYER REACHING -10C FOR ICE SEEDING. THIS SHOULD RESULT IN SHOWERS. THE QUESTION IS IN THE EXTENT OF COVERAGE. WHERE MOISTURE DEPTH LOOKS SUPPORTIVE OF PRECIP...HAVE USED 20-30 PERCENT POP. HOWEVER...IF FORECAST SOUNDINGS DO VERIFY...THERE IS SOME CONCERN THAT THIS MAY BE TOO CONSERVATIVE. THE SHOWERS WILL DIE OUT TONIGHT AS THE SHORT WAVE PASSES...AND CLOUDS SHOULD BEGIN TO THIN OUR FROM WEST TO EAST. WITH ENOUGH CLEARING...FROST COULD BE A CONCERN...AND HAVE INCLUDED PATCHY FROST IN OUR WESTERN COUNTIES...ESPECIALLY VALLEYS. NOT ENOUGH CONFIDENCE FOR WIDESPREAD FROST TO CONSIDER AN ADVISORY AT THIS POINT. WILL LET DAY SHIFT CONTINUE TO MONITOR THIS. COOL HIGH PRESSURE DRIFTING OVERHEAD FROM THE NW UNDER NW FLOW ALOFT ON SUNDAY WILL BRING SUNSHINE. .LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY) ISSUED AT 354 AM EDT SAT OCT 18 2014 EASTERN KY WILL FIND ITSELF UNDER A BRIEF AREA OF SURFACE HIGH PRESSURE AS AN EXITING TROUGH 0Z MONDAY CONTINUES IT/S WAY EASTWARD. THIS WILL KEEP DRY AND MOSTLY CLEAR SKIES ACROSS THE REGION FOR THE OVERNIGHT HOURS SUNDAY NIGHT. OPTIMAL RADIATIONAL COOLING WILL LEAD TO A DECENT RIDGE VALLEY SPLIT IN TEMPERATURES. WILL KEEP WITH PREVIOUS FORECAST/S MENTION OF POTENTIAL FROST DEVELOPMENT DURING THIS TIME FRAME IN THE COOLER VALLEY REGIONS. THE NEXT INCOMING UPPER LEVEL TROUGH WILL BEGIN INFLUENCING THE CWA A FEW HOURS LATER SUNDAY NIGHT. AN UPPER LEVEL SHORTWAVE-TURNED-TROUGH...ALONG WITH A SURFACE COLD FRONT WILL APPROACH THE REGION...INCREASING CLOUD COVER ACROSS EASTERN KY...AND SHIFTING WINDS TO A MORE SWRLY DIRECTION DURING THE NIGHT. IT WILL ALSO PULL IN CHANCES OF RAIN SHOWERS TO MUCH OF EASTERN KY...ESPECIALLY THE NORTH AND FAR EASTERN PORTIONS OF THE CWA. THE ECMWF AND GFS SOLUTIONS ARE STARTING TO LINE UP A LITTLE BETTER THAN RUNS FROM 24 HOURS AGO IN REGARDS TO THE EXTENT OF THE PRECIP...HOWEVER THEY ARE STILL LACKING A BIT IN TIMING AGREEMENT. THE ECMWF MOVES THE PRECIP INTO THE AREA 3 TO 6 HOURS FASTER THAN THAT OF THE GFS. GIVEN A CONSENSUS BETWEEN THE TWO...EXPECT BEST PRECIP CHANCES TO BEGIN ARRIVING BETWEEN 12 AND 18Z MONDAY. CLOUD COVER WILL HINDER BEST WARMING...WITH HIGHS ONLY EXPECTED TO REACH THE LOW 60S YET AGAIN. AS THE UPPER LEVEL SHORTWAVE CONTINUES IT/S EASTWARD TRACK...IT WILL PRODUCE A DEEPENING TROUGH AND EVENTUALLY A CLOSED LOW AS IT REACHES OUR CWA. AS THIS OCCURS...MODEL CONSENSUS SHOWS PRECIP CONTINUING ACROSS PORTIONS OF EASTERN KY THROUGH THE DAY TUESDAY AS WELL...ESPECIALLY IN THE UPSLOPE REGIONS OF FAR SE KY UNDER THE INFLUENCE OF NW TO N WINDS. THE UPPER LEVEL LOW WILL THEN BECOME STAGNANT...KEEPING THE POSSIBILITY FOR UPSLOPE MOISTURE AND SHOWERS IN THE FAR EAST THROUGH THE DAY WEDNESDAY. FOR THURSDAY INTO FRIDAY...EXPECT THE LOW TO FINALLY SHIFT FAR ENOUGH EASTWARD THAT DRY CONDITIONS SHOULD PREVAIL ACROSS THE ENTIRETY OF EASTERN KY. WHILE THE RAIN AND CLOUD COVER ARE IN PLACE...EXPECT NEAR NORMAL LOWS...BUT HIGHS WILL NOT BE ABLE TO REACH THEIR MAX POTENTIAL...ONLY HITTING THE LOW 60S. ONCE THE RAIN MOVES OUT AND A MUCH COOLER AIR MASS MOVES INTO PLACE...EXPECT TEMPERATURES TO DROP TO WELL BELOW NORMAL FOR THE REMAINDER OF THE EXTENDED. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING) ISSUED AT 801 AM EDT SAT OCT 18 2014 CONDITIONS WERE MOSTLY VFR AT THE START OF THE PERIOD IN EASTERN KY...WITH CLEAR SKIES IN OUR SW COUNTIES AND CEILINGS OF 4-5K FT AGL OVER MUCH OF THE NE PART OF THE AREA. DURING THE DAY...THE CEILINGS WILL SHOW AN OVERALL EXPANSION TO THE SOUTH AND LOWER IN HEIGHT. MOST LOCATIONS ARE EXPECTED TO BECOME MVFR IN THE AFTERNOON. AS COOLING ALOFT OCCURS DURING THE DAY...THE CLOUD DEPTH WILL GROW GREATER...AND ISOLATED TO SCATTERED SHOWERS ARE EXPECTED TO DEVELOP GENERALLY NORTH AND EAST OF THE CUMBERLAND RIVER BASIN LATE IN THE DAY. THE SHOWERS SHOULD DIE OUT IN THE EVENING. MVFR CEILINGS SHOULD BEGIN TO BREAK UP TONIGHT...ESPECIALLY LATE. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...HAL LONG TERM...JMW AVIATION...HAL

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