Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 150609 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 209 AM EDT TUE APR 15 2014 .UPDATE...
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ISSUED AT 208 AM EDT TUE APR 15 2014 UPDATED TO REMOVE THE THREAT OF THUNDER AS ALL THE INSTABILITY IS BOTTLED UP WELL TO OUR SOUTH NEAR THE GULF COAST. PRECIPITATION IS NOW SPREADING INTO FAR EASTERN KENTUCKY WITH THE COLD FRONT STRETCHED FROM NEAR MOREHEAD...SOUTH TO BETWEEN LONDON AND SOMERSET. THIS FRONT WILL CLEAR OUR EASTERN COUNTIES OVER THE NEXT FEW HOURS WITH THE BIG TEMPERATURE DROP COMMENCING AREAWIDE. LOWS HAVE ALREADY FALLEN INTO THE LOW 40S JUST UPSTREAM IN FRANKFORT WITH 30S BACK TOWARDS KCVG. LOOKING MORE LIKELY WE WILL SEE A PERIOD OF SNOW FOR MOST AREAS AROUND DAYBREAK AS MODELS HAVE CERTAINLY TRENDED COLDER. WITH THIS IN MIND...WILL EXPAND THE THREAT FOR SOME LIGHT SNOW ACCUMULATIONS TO MORE OF THE RIDGETOPS. VALLEYS WILL LAG QUITE A BIT IN TEMPERATURES...SO MAY NOT BE COLD ENOUGH FOR ACCUMULATIONS UNTIL THE SNOW IS VIRTUALLY DONE. GIVEN THE COLD TEMPERATURES IN THE HIGH ELEVATIONS ABOVE 2000 FEET...IT DOES LOOK LIKE 1 TO 3 INCHES CAN BE EXPECTED ON THOSE RIDGETOPS. PLENTY OF MOISTURE AND LIFT THIS MORNING TO SUPPORT PRECIPITATION THROUGH MUCH OF THE MORNING...ESPECIALLY ACROSS SOUTHEAST KENTUCKY. ALSO PLAN TO UPGRADE OUR FREEZE WATCH TO A FREEZE WARNING THIS MORNING UPDATE ISSUED AT 1100 PM EDT MON APR 14 2014 DID A FINAL EVENING UPDATE TO THE GRIDS AND ZONES TO REFLECT THE LATEST OBSERVATIONAL TRENDS AND HI-RES MODEL GUIDANCE. THEY CONTINUE TO INDICATE THAT THE PCPN WILL CHANGE OVER TO A BIT OF SNOW JUST ABOUT EVERYWHERE FROM 09Z WEST TO 12Z EAST AND THEN TAPER OFF QUICKLY DURING THE MORNING. WARM GROUND TEMPERATURES AND THE STILL UN-CHILLED LOWEST BOUNDARY LAYER OF AIR WILL MAKE ANY ACCUMULATIONS INTO EARLY TUESDAY VERY FLEETING ON DECKS OR GRASSY SPOTS...EXCEPT UP TO 2 INCHES WILL BE POSSIBLE ABOVE 2000 FEET NEAR THE VIRGINIA BORDER. THE SNOW WILL BE MIXED WITH RAIN AS SOME OF IT SHOULD BE ABLE TO MELT IN THE LAST COUPLE OF HUNDRED FEET DESPITE QUITE COOL TEMPS JUST A BIT HIGHER ALOFT. THE GRIDS...AND A FRESHENED SET OF ZONES...HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATE ISSUED AT 820 PM EDT MON APR 14 2014 TWEAKED THE TEMP...DEWPOINT...POP...AND SKY COVER GRIDS TO REFLECT CURRENT CONDITIONS AND TRENDS. HAVE TIMED THE RETURN OF SHOWERS... AND A POSSIBLE THUNDERSTORM...INTO THE AREA AFTER 10 PM SPREADING GRADUALLY EAST JUST AHEAD OF THE COLD FRONT. THIS WILL REACH FAR EAST KENTUCKY LAST...LIKELY NOT UNTIL AFTER 06Z...PER THE LATEST HRRR. THE GRIDS HAVE BEEN SENT TO THE NDFD AND WEB SERVERS. UPDATE ISSUED AT 620 PM EDT MON APR 14 2014 21Z SFC ANALYSIS SHOWS A POTENT COLD FRONT APPROACHING CENTRAL KENTUCKY IN CONJUNCTION WITH THE DEEP SPRING LOW SPINNING OVER THE EASTERN GREAT LAKES. A WAVE WILL LIFT NORTH ALONG THIS BOUNDARY LATER TONIGHT AND SPREAD...MORE SUBSTANTIAL...PCPN BACK OVER EAST KENTUCKY. ON RADAR...A LARGE AREA OF SHOWERS AND A FEW EMBEDDED THUNDERSTORMS ARE MOVING THROUGH WESTERN KENTUCKY ACCOMPANYING THE COLD FRONT. HERE IN THE EAST WE ARE DRY WITH TEMPERATURES IN THE UPPER 60S AND LOWER 70S ALONG WITH A FEW BREAKS IN THE CLOUD COVER. DESPITE THESE BREAKS...WINDS HAVE BEEN CONTAINED IN THE 10 TO 20 MPH RANGE WITH ONLY OCCASIONAL GUSTS TO 30 MPH. MEANWHILE...DEWPOINTS REMAIN LOWEST THROUGH FAR EAST KENTUCKY WHERE SOME UPPER 40S ARE FOUND WHILE MID 50S EXIST FURTHER WEST. THIS EXTRA BIT OF DRY AIR WILL HELP TO HOLD OFF THE RETURNING RAIN SHOWERS FOR A BIT LONGER. WENT AHEAD AND UPDATED THE FORECAST TO DROP THE LAKE WIND ADVISORY AS THE WINDS ARE RUNNING AROUND 10 MPH BELOW CRITERIA. ALSO ADJUSTED THE FORECAST INTO TUESDAY MORNING FOR TIMING THE SHOWERS...AND POSSIBLY THUNDERSTORMS...INTO THE AREA LATER THIS EVENING AND OVERNIGHT. ALSO ADJUSTED THE WX GRIDS FOR THE SNOW CHANCES LATE TONIGHT AND THROUGH THE DAY TUESDAY. MADE SOME MINOR TWEAKS TO TEMPERATURES AND DEWPOINTS THIS EVENING AND INTO TUESDAY MORNING BASED ON THE CURRENT CONDITIONS...TRENDS...AND THE LATEST MODEL GUIDANCE. HAVE UNDERCUT THE CONSSHORT TEMPERATURES LATE TONIGHT AND EARLY TUESDAY AS IT APPEARS TO BE UNDER DOING THE POST FRONTAL CAA. THESE GRIDDED FORECAST UPDATES HAVE BEEN SENT TO THE NDFD AND WEB SERVERS WHILE THE TEXT PRODUCTS HAVE BEEN UPDATED WITH THE CHANGES DESCRIBED ABOVE.
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&& .SHORT TERM...
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(THIS EVENING THROUGH TUESDAY NIGHT) ISSUED AT 340 PM EDT MON APR 14 2014 AFTER COMPARING ALL THE LATEST MODEL DATA TO THE ACTUAL WEATHER CONDITIONS OVER THE PAST FEW HOURS...THE NAM12 BY FAR AND AWAY HAS BEEN HANDLING THINGS THE BEST AND HAD THE BEST INITIALIZATION. THEREFORE...THE NAM12 SOLUTION WAS USED TO CREATE THIS AFTERNOONS FORECAST PACKAGE THROUGH WEDNESDAY MORNING. WITH NO PRECIPITATION ONGOING...AND NOTHING AT ALL APPROACHING FROM UPSTREAM...THE AREA SHOULD REMAIN FREE OF RAIN FOR THE NEXT SEVERAL HOURS. ISOLATED RAIN SHOWERS SHOULD BEGIN POPPING UP AND MOVING INTO THE AREA EARLY THIS EVENING...AS A STRONG COLD FRONT BEGINS TO PUSH EASTWARD TOWARD THE AREA. NUMEROUS RAIN SHOWERS AND A FEW THUNDERSTORMS WILL BE POSSIBLE OVERNIGHT...AS THE FRONT MOVES ACROSS THE AREA. THE PERIOD BETWEEN 4 AND 8Z LOOKS TO BE THE IDEAL TIME FOR ANY THUNDER WE EXPERIENCE AS THAT WILL BE THE TIME OF BEST LOW LEVEL WARM MOISTURE FEED. ONCE THE FRONT MOVES BY...MUCH COLDER AIR WILL QUICKLY SPILL INTO THE AREA BEHIND IT. THIS WILL BE WHEN WE COULD SEE SOME SNOW FLAKES FLYING AND PERHAPS EVEN A BIT OF SLEET. WITH GROUND TEMPERATURES EXTREMELY WARM THE PAST SEVERAL DAYS...AND WITH THE SOILS ALREADY WET FROM RAIN...IT WILL VERY HARD FOR ANY SNOW TO ACCUMULATE. THE ONE EXCEPTION WOULD BE THE HIGHER TERRAIN ALONG THE VIRGINIA AND WEST VIRGINIA BORDERS...WHERE THE TALLEST PEAKS COULD SEE MAYBE UP TO AN INCH OF SNOW. ONCE THE FRONT MOVES ACROSS THE AREA LATER TONIGHT...TEMPERATURES WILL BEGIN FALLING STEADILY THROUGH THE PREDAWN HOURS. TEMPERATURES WILL STILL RISE DURING THE DAY ON TUESDAY...BUT WILL NOT RISE VERY MUCH AS A COLD AIR MASS SETTLES OVER THE AREA. HIGH TEMPERATURES FOR MOST LOCATIONS ON TUESDAY WILL LIKELY STRUGGLE TO REACH 40 DEGREES. THE MOST PRESSING MATTER FOR THIS PERIOD OF THE FORECAST WILL BE THE FRIGID TEMPERATURES WE ARE EXPECTING TUESDAY NIGHT INTO WEDNESDAY MORNING. AN ARCTIC AIR MASS WILL HAVE FULLY SETTLED OVER THE REGION TOMORROW NIGHT...ALLOWING TEMPERATURES TO PLUMMET INTO THE LOW TO MID 20S FOR MOST FOLKS. SOME OF OUR COLDER VALLEYS AND TALLEST MOUNTAIN PEAKS MAY EVEN SEE THE MERCURY DIP INTO THE UPPER TEENS. WITH WINDS GOING NEAR CALM MOST OF THE NIGHT...AND WITH SKIES BEING MOSTLY CLEAR...THE STAGE WILL BE SET FOR A WIDESPREAD KILLING FREEZE EVENT. WIDESPREAD FROST WILL BE POSSIBLE FOR MOST OF THE NIGHT AND INTO EARLY WEDNESDAY MORNING. TEMPERATURES THIS COLD WILL EASILY KILL ANY SENSITIVE OUTDOOR VEGETATION THAT IS LEFT UNPROTECTED. A FREEZE WATCH IS CURRENTLY IN EFFECT TO ADDRESS THIS ISSUE...BUT THIS PRODUCT WILL LIKELY BE UPGRADED TO A FREEZE WARNING BY THE UPCOMING NIGHT SHIFT EARLY TOMORROW MORNING. .LONG TERM...(WEDNESDAY THROUGH MONDAY) ISSUED AT 348 PM EDT MON APR 14 2014 THE MODELS START OUT IN GOOD AGREEMENT WITH AN UPPER TROUGH EXITING THE EAST COAST FAIRLY ZONAL FLOW ACROSS THE REST OF THE CONUS. AN UPPER TROUGH AND ASSOCIATED FRONT SYSTEM IS OVER THE DAKOTAS. THIS UPPER TROUGH DEEPENS WITH TIME AND SLOWLY PUSHES A COLD FRONT TOWARD THE AREA. THE FRONT SHOULD BE MOVING ACROSS EASTERN KENTUCKY ON FRIDAY NIGHT. LEFT SOME PRECIPITATION IN THE FORECAST FOR FRIDAY...HOWEVER WOULD NOT BE TOO SURPRISED TO SEE ANY PRECIPITATION TO BE DELAYED UNTIL FRIDAY NIGHT. THIS IS WHERE THE MODES BEGIN TO DISAGREE WITH THE GFS A LITTLE FASTER THAN THE ECMWF...WHICH IS THE PREFERRED MODEL. HIGH PRESSURE BUILDS IN BEHIND THE FRONT AND WILL KEEP THINGS DRY THROUGH THE END OF THE PERIOD. FOR TEMPERATURES...NUDGED THE MODEL BLENDS TOWARD THE NEW ECMWF WHICH WAS TYPICALLY COOLER THAN THE BLEND.
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&& .AVIATION...
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(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT) ISSUED AT 208 AM EDT TUE APR 15 2014 VFR CONDITIONS CONTINUE TO GIVE WAY TO LOWER MVFR/IFR CIGS. THIS TREND WILL CONTINUE OVER THE NEXT FEW HOURS...WITH CIGS FALLING TO BETWEEN 600 AND 800 FEET THROUGH THE REMAINDER OF THE NIGHT. THIS WILL CIGS NEAR AIRPORT MINIMUMS. IN ADDITION...WINDS WILL CONTINUE TO SHIFT AROUND TO THE WEST AND EVENTUALLY NORTHWEST. RAIN WILL MIX WITH AND CHANGE TO SNOW IN SOME AREAS AROUND DAYBREAK...BEFORE ENDING BY EARLY AFTERNOON. AS WE HEAD THROUGH THE DAY WE SHOULD EVENTUALLY GO BACK TO MVFR AND VFR BY LATE AFTERNOON. HOWEVER...SOME QUESTION AS TO HOW FAST THIS INCREASE TAKES PLACE.
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&& .JKL WATCHES/WARNINGS/ADVISORIES...
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FREEZE WARNING FROM 8 PM THIS EVENING TO 10 AM EDT WEDNESDAY FOR KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120.
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&& $$ UPDATE...KAS SHORT TERM...AR LONG TERM...JJ AVIATION...KAS

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