Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 260854 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 354 AM EST FRI DEC 26 2014 .SHORT TERM...(TODAY THROUGH SATURDAY) ISSUED AT 307 AM EST FRI DEC 26 2014 EARLY THIS MORNING...AN UPPER LEVEL RIDGE WAS CENTERED NEAR CUBA WITH THE RIDGE AXIS EXTENDING NORTH INTO THE SOUTHEASTERN US...APPALACHIANS TO THE CENTRAL GREAT LAKES REGION. MEANWHILE AS TROUGH WAS OVER THE ROCKY MOUNTAIN REGION WITH A CLOSED LOW OVER THE FOUR CORNERS REGION. A DEEP CLOSED LOW WAS ALSO OVER EASTERN CANADA. AT THE SFC...HIGH PRESSURE WAS CENTERED OVER THE CENTRAL AND SOUTHERN APPALACHIAN REGION. ASSOCIATED WITH THIS RIDGE WAS A VERY DRY AIRMASS AND THE OBSERVATIONS FROM THE HIGHER TERRAIN ABOVE 2500 FEET HAVE EXPERIENCED THE SUBSIDENCE INVERSION SURFACING. THESE HIGHER RIDGES ARE IN THE LOWER 40S WITH DEWPOINTS IN THE SINGLE DIGITS ABOVE ZERO TO THE LOWER TEENS. AS EXPECTED...THE POSITION OF THIS HIGH IS FAVORABLE FOR A RIDGE/VALLEY TEMPERATURE SPLIT AND THIS IS EVIDENCED BY CURRENT OBSERVATION RANGING FROM THE MID 20S IN THE NORMALLY COLDER VALLEY LOCATIONS TO THE LOWER 40S. THE RIDGES IN THE LOWER TERRAIN ARE CURRENTLY NEAR THE FREEZING MARK. OBSERVATIONS FROM EARLIER INDICATED SOME VALLEY FOG. OTHER THAN THE PATCHY EARLY VALLEY FOG AND POSSIBILITY OF THIS BEING PATCHY FREEZING FOG...THROUGH AROUND DAWN. SOME OF THIS MAY DISSIPATE AND JUST GO INTO FROST FORMATION...SO HAVE ONLY KEPT THIS AS PATCHY. THE UPPER LEVEL AND SFC RIDGE WILL DOMINATE TODAY INTO TONIGHT. SOME OF THE VERY DRY AIR ALOFT WILL MIX DOWN ESPECIALLY IN THE SOUTHEASTERN COUNTIES AND SOME LOW MIN HUMIDITY IS ANTICIPATED...ESPECIALLY ABOVE 2000 FEET. MIN RH OF 20 TO 30 PERCENT SHOULD BE COMMON OVER THE SOUTHEASTERN COUNTIES...WITH MIN RH FROM THE HIGH SINGLE DIGITS TO THE TEENS ABOVE 2000 FEET. FURTHER TO THE WEST TEMPERATURES SHOULD BE COLDER AND DEWPOINT NOT AS LOW. THE SFC AND UPPER LEVEL RIDGE WILL DEPART TO THE EASTERN SEABOARD LATER TODAY AND INTO TONIGHT...BUT WITH THE RELATIVELY DRY AIR REMAINING IN PLACE...ANOTHER RIDGE/VALLEY TEMPERATURE SPLIT IS ANTICIPATED. MEANWHILE...THE TROUGH INITIALLY OVER THE ROCKIES WILL BEGIN TO MOVE EAST INTO THE PLAINS THROUGH SATURDAY. A LEAD SHORTWAVE AND A NORTHERN STREAM TROUGH SHOULD INTERACT TO LEAD TO A WAVE OR SERIES OF WAVES OF LOW PRESSURE MOVING NORTHEAST ALONG A BAROCLINIC ZONE THAT CURRENTLY EXTENDS FROM THE NORTHERN GREAT LAKES TO THE CENTRAL PLAINS TO THE SOUTHERN ROCKIES. AS THE WAVE OF LOW PRESSURE TRACKS INTO THE CENTRAL GREAT LAKES THIS TRAILING BUT WAVY SFC COLD FRONT SHOULD REACH THE LOWER OH VALLEY AND POSSIBLY ENTER THE COMMONWEALTH BEFORE THE END OF THE PERIOD. HOWEVER...GIVEN THE CURRENTLY DRY AIRMASS IN PLACE THAT IS EXPECTED TO LINGER INTO EARLY ON SATURDAY...IT WILL TAKE A WHILE FOR MOISTURE ADVECTION TO BE SUFFICIENT FOR RAIN SHOWERS TO ENTER EASTERN KY. IN FACT...THESE SHOULD BE CLOSER TO THE FRONT INITIALLY AND MOST OF...IT NOT THE ENTIRE CWA SHOULD REMAIN DRY THROUGH SUNSET ON SATURDAY. HOWEVER...THE WEEKEND SHOULD END RATHER WET WITH STEADIER RAIN SPREADING INTO THE AREA JUST AFTER THE END OF THE PERIOD. THE DRY AIRMASS WILL WARM RATHER WELL TODAY AND MAX T SHOULD AVERAGE 10 TO 15 DEGREES ABOVE NORMAL. TEMPERATURES ON SATURDAY SHOULD BE SLIGHTLY MILDER AND EVEN FURTHER ABOVE NORMAL. EVEN OVERNIGHT LOWS TONIGHT SHOULD AVERAGE ABOUT 10 DEGREE ABOVE NORMAL ON THE RIDGES AND A COUPLE OF DEGREES ABOVE NORMAL FOR VALLEY LOCATIONS. .LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY) ISSUED AT 349 AM EST FRI DEC 26 2014 THE PERIOD WILL BEGIN WITH A SLOW MOVING COLD FRONT SLOWLY PROGRESS EAST AS SURFACE HIGH MOVES EAST INTO THE ATLANTIC. THIS SLOW MOVING FRONT WILL HAVE SEVERAL AREAS OF LOW PRESSURE MOVE ALONG THE BOUNDARY. ONSET OF PRECIP COULD BE SLOWED DUE TO DOWNSLOPING...HOWEVER MOISTURE WILL EVENTUALLY DEEPEN AS WE MOVE INTO SUNDAY. NO TREAT OF WINTER PRECIP AS TEMPERATURES ARE EXPECTED TO BE ABOVE NORMAL DURING THIS PERIOD. THIS FRONTAL BOUNDARY AND ELONGATED TROUGH WILL MOVE EAST WITH THE TROUGH BEGINNING TO FLATTEN OUT SUNDAY NIGHT. HIGH PRESSURE WILL PROGRESS EAST BEHIND THE COLD FRONT AND THIS WILL ALSO USHER IN COOLER CLOSER TO NORMAL TEMPERATURES ON MONDAY INTO TUESDAY. THIS HIGH PRESSURE WILL KEEP WEATHER FAIRLY QUIET AND TEMPS GENERALLY BELOW NORMAL THROUGH MUCH OF THE LONG TERM PERIOD. TUESDAY NIGHT THERE IS A WEAK SHORT WAVE THAT CROSSES THE AREA WITH MAINLY A BIT MORE CLOUD COVER ACROSS THE REGION. THIS WILL KEEP FROM GAINING MAX COOLING AND COULD EVEN BRING POTENTIAL OF SOME FLURRIES...HOWEVER CONFIDENCE IS LOW ON THIS AT THIS POINT GIVEN HOW DRY IT WILL BE. ALSO BASED ON MODEL SOUNDING THE MOISTURE IS QUITE SHALLOW. HIGH WILL CONTINUE TO BUILD EAST BRINGING MOSTLY CLEAR SKIES AS WE MOVE INTO LATER WEDNESDAY AND WEDNESDAY NIGHT. GIVEN THAT HIGH WILL BE MOSTLY CRESTING ACROSS THE REGION AND MOSTLY CLEAR SKIES WOULD EXPECT THIS TO ONE OF THE COLDER NIGHTS WITH GOOD RADIATIONAL COOLING. RIGHT NOW GOING WITH LOW TEMPS IN THE UPPER TEEN TO LOWER 20S WED NIGHT. MOVING INTO THURSDAY MORE UNCERTAINTY EXISTS WITH 500MB SHORTWAVE EJECTING OUT OF THE FOUR CORNER AND HOW QUICKLY MOISTURE SPREADS NE AHEAD OF DEVELOPING LOW PRESSURE SYSTEM ACROSS SOUTHERN TX. RIGHT NOW JUST KEPT SLIGHT CHANCE OF MIX RAIN/SNOW BEFORE CHANGING TO RAIN ON THURSDAY...HOWEVER CONFIDENCE IS LOW ON HOW MUCH OF THIS SYSTEM WILL BE OCCURRING ON THURSDAY VERSUS FRIDAY. && .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT) ISSUED AT 135 AM EST FRI DEC 26 2014 HIGH PRESSURE WILL BRING MOSTLY VFR TO THE ENTIRE REGION THROUGH THE PERIOD. THE ONLY EXCEPTION TO THIS IS SOME MVFR OR LOCALLY LOWER FOG IN THE DEEPER NON TAF SITE VALLEY LOCATIONS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...DJ AVIATION...JP

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