Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 220331 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1031 PM EST FRI NOV 21 2014 .UPDATE...
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ISSUED AT 1031 PM EST FRI NOV 21 2014 AFTER WATCHING TRENDS IN HOURLY TEMPERATURES ACROSS EASTERN KENTUCKY THE PAST FEW HOURS...IT APPEARS THAT THE CURRENT FORECAST WILL SUFFICE AS IS. IN A NUTSHELL...THE CURRENT TEMPERATURE CURVE HAS BECOME QUITE COMPLEX WITH SOME STATIONS ALONG THE VIRGINIA ACTUALLY WARMING SLIGHTLY AS WEAK SOUTHEAST FLOW DESCENDS DOWN THE MOUNTAINS. OTHER LOCATIONS HAVE COOLED OFF A LOT MORE QUICKLY THAN THE ORIGINAL FORECAST HAS BEEN DEPICTING SO FAR...BUT SOME OF THOSE OBS POINTS WILL LIKELY START WARMING LATER TONIGHT AS WARM AIR ADVECTION BECOMES STRONGER. LASTLY...A NUMBER OF OUR VALLEYS...PARTICULARLY IN THE NORTHEAST...HAVE ALREADY DECOUPLED...SETTING THINGS UP FOR A WELL DEFINED RIDGE VALLEY SPLIT. BASED ON ALL THAT...WILL LET THE CURRENT FORECAST RIDE AS IS. UPDATE ISSUED AT 733 PM EST FRI NOV 21 2014 JUST ISSUED A NEW SET OF ZONES FEATURING CHANGES MADE TO THE TEMPERATURE FORECAST FOR NEXT THURSDAY...THURSDAY NIGHT AND FRIDAY TIME PERIOD. THE TEMPERATURES WE HAD IN THE FORECAST BEFORE FOR THIS PART OF THE FORECAST PERIOD WERE AT LEAST 6 TO 7 DEGREES WARMER THAN SOME OF OUR NEIGHBORS. THE DEW POINTS AND WEATHER GRIDS WERE ALSO RERAN BASED ON THE NEW TEMPERATURES. UPDATE ISSUED AT 635 PM EST FRI NOV 21 2014 THE FORECAST HAS BEEN ON TRACK SO FAR THIS EVENING...SO NO UPDATE IS PLANNED AT THIS TIME. HOWEVER...SOME OF OUR FORECAST GRIDS FOR NEXT THURSDAY AND THURSDAY NIGHT ARE QUITE A BIT OUT OF SYNC WITH SOME OF OUR NEIGHBORS...SO SOME ADJUSTMENTS WILL BE MADE TO CORRECT THIS ISSUE LATER IN THE SHIFT...ALONG WITH ANY OTHER NECESSARY UPDATES.
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&& .SHORT TERM...(THIS EVENING THROUGH SATURDAY NIGHT) ISSUED AT 335 PM EST FRI NOV 21 2014 SURFACE HIGH PRESSURE PASSING OVER THE REGION TODAY WILL MOVE TO OUR EAST TONIGHT...WITH WARM AIR ADVECTION BEGINNING AS LOW LEVEL FLOW TURNS TO THE SOUTH. ISENTROPIC LIFT IN THE WARM AIR ADVECTION WILL ALSO BRING SOME CLOUDS TO THE REGION LATE TONIGHT AND SATURDAY... ESPECIALLY IN OUR FAR NW COUNTIES. HOWEVER...MODEL TRENDS SUGGEST THAT ANY PRECIP SHOULD REMAIN NW OF THE JKL FORECAST AREA. AN UPPER LOW/SHORTWAVE TROUGH OVER THE FAR SW CORNER OF THE CONUS TODAY WILL MOVE TO TX SATURDAY NIGHT...BEFORE THEN TURNING NE AND PHASING WITH A NORTHERN STREAM SYSTEM CATCHING UP WITH IT. THIS SYSTEM WILL JUST BE STARTING TO TAKE SHAPE AT THE END OF THE PERIOD...AND WILL RESULT IN INCREASING CLOUDS AND AN INCREASE IN LOW LEVEL FLOW FOR OUR LOCAL AREA. IT STILL APPEARS THAT PRECIP WITH THIS SYSTEM WILL HOLD OFF UNTIL AFTER SATURDAY NIGHT. THAT BEING SAID...TEMPERATURES COULD BE THE TRICKIEST PART OF THE SHORT TERM PERIOD. OUR FIRST NIGHT WILL START OUT WITH A TYPICAL DIURNAL DOWNTURN IN TEMPS...WITH VALLEYS LEADING THE WAY. HOWEVER...AS LOW LEVEL FLOW INCREASES DURING THE NIGHT...RIDGES AS WELL AS OPEN TERRAIN IN THE WESTERN PART OF THE FORECAST AREA SHOULD SEE TEMPS LEVEL OFF OR EVEN RISE OVERNIGHT. CLOUDS IN THE FAR NW TOWARD DAWN WILL ALSO AID IN THIS TREND. MEANWHILE...VALLEYS IN THE EAST WILL LIKELY MAINTAIN THEIR COLD READINGS OVERNIGHT...OR EVEN CONTINUE TO FALL VERY SLOWLY. EXACTLY WHERE THE TRANSITION FROM ONE TEMPERATURE REGIME TO THE OTHER OCCURS WILL BE VERY DIFFICULT TO DELINEATE. SKIES BECOMING PARTLY TO MOSTLY SUNNY ON SATURDAY...ALONG WITH TEMPS ALOFT CONTINUING TO WARM...WILL ALLOW FOR A SUBSTANTIAL WARM-UP TO NEAR NORMAL READINGS. THE TEMPERATURE FORECAST FOR SATURDAY NIGHT WILL POSE ESSENTIALLY THE SAME CHALLENGES AS TONIGHT... EXCEPT LOW LEVEL FLOW WILL BECOME STRONGER...AND CLOUDS WILL BE ON THE INCREASE NOT ONLY IN THE NW BUT ALSO IN THE SW PART OF THE AREA. .LONG TERM...(SUNDAY THROUGH FRIDAY) ISSUED AT 335 PM EST FRI NOV 21 2014 UPPER LEVEL SHORTWAVE IS EXPECTED TO BE CENTERED NEAR AND AROUND THE ARKLATEX REGION BY SUNDAY MORNING. THIS UPPER LEVEL FEATURE WILL TRACK NE AS IT BEGINS TO PHASE WITH THE LONG WAVE TROUGH LOCATED IN THE WESTERN US EARLY NEXT WEEK. THIS WILL CONTINUE TO DEEPEN A ASSOCIATED SURFACE LOW THAT WILL TRACK NE INTO THE MIDDLE MISSISSIPPI RIVER VALLEY. ATTENDANT WARM FRONT WILL CONTINUE TO SURGE NORTH THROUGH THE DAY SUNDAY. THE 06Z GFS CONTINUES TO MOVE PRECIP IN SLOWER WHILE THE 00Z ECMWF/06 NAM ARE A BIT FASTER. PREVIOUS FORECAST HAD A GRADIENT AND LEANED THAT DIRECTION GIVEN THAT IT IS A DECENT COMPROMISE TO SOME OF THE TIMING DIFFERENCES THAT HAVE BEEN SEEN. THERE COULD BE A DOWNSLOPE COMPONENT TO THIS SYSTEM AS MENTIONED IN PREVIOUS DISCUSSION...HOWEVER I THINK THIS WOULD BE TRANSLATED MORE IN THE QPF. THEREFORE PLAN TO PUT HIGHER POPS IN THE FORECAST FOR SUNDAY AFTERNOON SINCE RAIN DOES LOOK AT LEAST LIKELY. RAIN WILL DIE OFF SUNDAY NIGHT AS WARM FRONT CONTINUES TO MOVE NORTH OF THE REGION. THIS WARM FRONT DOES FINALLY BRING SOME SLIGHTLY ABOVE NORMAL HIGH TEMPS ACROSS THE CWA SUNDAY. MOVING INTO MONDAY EXPECT A COLD FRONT TO CROSS THE REGION THROUGH THE DAY. GIVEN DRIER AIR FILTERING IN ALOFT LIGHTER QPF AND POP AMOUNTS WILL BE MORE SLIGHT TO CHANCE SIDE. GIVEN DECENT MIXING AND STRONG UPPER LEVEL JET ACROSS THE REGION WILL LEAD TO A BREEZY DAY ACROSS THE REGION. SURFACE HIGH BEGINS TO NUDGE EAST AS WE MOVE INTO TUESDAY WITH GENERALLY DEEP TROUGH MOVING ACROSS MUCH OF THE EASTERN US. MODELS DO COME INTO BETTER AGREEMENT ON DISTURBANCE LATER WEDNESDAY INTO THURSDAY. AT THIS TIME WILL STICK CLOSE TO MODEL CONSENSUS WHICH BRINGS SLIGHT POPS ACROSS THAT REGION. AFTER THIS ECMWF DEVELOPS A SURFACE LOW ACROSS THE SOUTHERN MISSISSIPPI RIVER VALLEY AND BRINGS IT NE INTO THE OHIO VALLEY BY LATE FRIDAY. WHILE THE GFS HAS A REFLECTION OF THIS MUCH LATER IN THE MODEL RUN. AGAIN GIVEN UNCERTAINTY WILL STICK CLOSE TO BLEND WHICH GIVES MORE IN THE WAY OF SLIGHT TO CHANCE POPS INTO FRIDAY. OVERALL TEMPERATURES ARE EXPECTED TO REMAIN BELOW NORMAL FROM TUESDAY THROUGH THE REST OF THE LONG TERM. && .AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING) ISSUED AT 635 PM EST FRI NOV 21 2014 VFR CONDITIONS AND WINDS LESS THAN 10KTS ARE EXPECTED THROUGH THE PERIOD. WE WILL SEE FLUCUATIONS IN CLOUD COVER FROM TIME TO TIME AS A WEAK WARM FRONT PASSES BY ON SATURDAY...BUT NOTHING MORE THAN THAT IS EXPECTED DURING THE TAF PERIOD AT THIS TIME. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...HAL LONG TERM...DJ AVIATION...AR

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