Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 132058 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 458 PM EDT SAT SEP 13 2014 .UPDATE... ISSUED AT 457 PM EDT SAT SEP 13 2014 BASED ON TRENDS IN SATELLITE IMAGERY...HAVE SLOWED THE DECREASE IN CLOUDS OVER OUR SE COUNTIES THIS EVENING. && .SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT) ISSUED AT 342 PM EDT SAT SEP 13 2014 A DISTURBANCE MOVING ACROSS THE LOWER GREAT LAKES HAS RESULTED IN A COLD FRONT EXPANDING DOWN ALONG THE ATLANTIC COAST. MOISTURE ASSOCIATED WITH THIS SYSTEM LED TO WIDESPREAD CLOUD COVERAGE ACROSS MUCH OF THE EASTERN US...INCLUDING THE OHIO RIVER VALLEY THROUGH THE MORNING HOURS. AN AREA OF STRONG SUBSIDENCE/DRY AIR IS CURRENTLY SHOWING UP ON WATER VAPOR AND VISIBLE IMAGERY FLOWING IN FROM THE CENTRAL PLAINS AND INTO THE OHIO RIVER VALLEY THIS AFTERNOON. CURRENTLY...CLOUDS ARE BREAKING UP ACROSS LMK/S CWA...WITH JKL EXPECTED TO FOLLOW SUIT LATE THIS AFTERNOON AND EVENING. CLOUD COVER KEPT HIGH TEMPS AT BAY TODAY...BUT SOME BRIEF CLEARING /ESPECIALLY IN THE NORTH/ BEFORE SUN DOWN COULD BE ENOUGH TO BOOST TEMPS UP ANOTHER COUPLE DEGREES BEFORE ALL IS SAID AND DONE. SURFACE HIGH PRESSURE...AND ZONAL FLOW WILL TAKE HOLD FOR THE REMAINDER OF THE SHORT TERM. UNLIKE LAST NIGHT...CLEARING SKIES WILL LEAD TO OPTIMAL RADIATIONAL COOLING /ESPECIALLY IN THE NORTH WHERE CLEARING IS EXPECTED TO OCCUR FIRST/ AND ALLOW TEMPS TO DROP TO WELL BELOW NORMAL FOR THIS TIME OF YEAR. OVERNIGHT LOWS COULD VERY POSSIBLY DROP INTO THE UPPER 40S ACROSS THE NORTHERN HALF OF THE CWA...AND LOW TO MID 50S ACROSS THE SOUTHERN HALF. FOR TOMORROW...CONVECTION FROM THE STATIONARY FRONT NEAR THE ATLANTIC WILL EXPAND DURING THE DAY. UNLIKE PREVIOUS DAYS...LATEST MODEL RUNS ARE STILL SUPPORTING THERE NOT BEING QUITE ENOUGH FORCING FOR THIS MOISTURE TO MAKE IT BACK INTO FAR SE KY. SO KEPT WITH PREVIOUS FORECAST/S IDEA OF LEAVING OUT ANY MENTION OF PRECIP HERE. OTHERWISE...DRY AIR AND HIGH PRESSURE WILL PREVAIL...WITH WRLY WINDS ALOFT AND NRLY WINDS AT THE SURFACE CONTINUING TO ADVECT IN COLDER AIR. HIGHS TOMORROW WILL BE SLIGHTLY WARMER THAN TODAY JUST GIVEN THE FACT THAT THE SUN WILL PLAY MORE OF AN INFLUENCE. HOWEVER...THEY WILL STILL BE QUITE BELOW NORMAL...ONLY REACHING THE LOW TO MID 70S ACROSS THE REGION. AS FAR AS FOG IS CONCERNED OVERNIGHT...SEVERAL FACTORS LED TO THIS NOT BEING INCLUDED IN THE FORECAST. FIRST IS JUST THE STRONG SUBSIDENCE THAT IS MOVING INTO THE REGION. NORMALLY THIS MAY LEAD TO THE ENTRAPMENT OF MOISTURE NEAR THE SURFACE AND ACTUALLY PROMOTE FOG DEVELOPMENT. HOWEVER...IN THIS CASE THERE IS JUST NOT MUCH MOISTURE TO WORK WITH. THERE IS SOME DISCREPANCY IN THE LATEST FORECAST SOUNDINGS. WHILE THE GFS IS POINTING TOWARDS POSSIBLE FOG...THE NAM IS LEANING MORE TOWARDS A LOW STRATUS DECK...BOTH WITH VERY LITTLE MOISTURE TO SUPPORT. MORE THAN LIKELY IF ANYTHING DOES DEVELOP...FAVOR MORE THE LOW STRATUS DECK SOLUTION...BUT EVEN THAT SHOULD BE PATCHY IF EXISTENT AT ALL. ALSO...THE WIND DIRECTION NEAR THE SURFACE WILL BE NRLY SHIFTING TO MORE NERLY. THIS DIRECTION IS GENERALLY NOT VERY CONDUCIVE TO FOG DEVELOPMENT IN THE REGION. .LONG TERM...(MONDAY THROUGH SATURDAY) ISSUED AT 200 PM EDT SAT SEP 13 2014 THE MODELS ARE IN PRETTY GOOD AGREEMENT ALOFT RIGHT ON THROUGH THE EXTENDED. FOR THE BULK OF THE TIME...A TROUGH WILL BE PRESENT THROUGH THE EASTERN HALF OF THE NATION WITH MAINLY WEAK SHORTWAVES PASSING ABOVE THE OHIO VALLEY IN NORTHWEST FLOW. HOWEVER...AT THE START OF THE EXTENDED ONE OF THE STRONGER WAVES WILL MOVE THROUGH JUST NORTH OF OUR AREA MONDAY NIGHT. THE TROUGH FLATTENS OUT A BIT IN THE WAKE OF THIS WAVE DURING THE MIDDLE PART OF THE WEEK. THE NEXT CONCENTRATED BATCH OF ENERGY WILL PASS THROUGH THE OHIO VALLEY TO CLOSE OUT THE WEEK BRINGING SOME BRIEF RESURGENCE TO THE TROUGH. THE MODEL AGREEMENT DOES START TO BREAKDOWN HEADING INTO THE WEEKEND WITH THE GFS ERASING THE TROUGH QUICKER THAN THE ECMWF IN RESPONSE TO STRONGER TROUGHING BUILDING THROUGH THE ROCKY MOUNTAIN STATES. SLIGHT RIDGING THEN FOLLOWS OVER THE AREA THROUGH THE DAY SATURDAY. HOWEVER...THERE IS SOME QUESTION CONCERNING THE STABILITY OF THE DEEPER WESTERN TROUGH SOLUTION FROM THE ECMWF THAT ALSO CASTS DOUBT ON THE STRENGTH OF THE DOWNSTREAM RIDGE OVER OUR REGION. HOWEVER... GIVEN THE SIMILARITIES IN THE MODELS...HAVE FAVORED A MODEL BLEND SOLUTION THROUGH THE FORECAST PERIOD. SENSIBLE WEATHER WILL FEATURE ONE AREA OF COOL HIGH PRESSURE MOVING OFF TO THE EAST DURING THE DAY MONDAY WHILE ANOTHER HEADS THIS WAY FROM THE NORTHERN PLAINS. BETWEEN THESE TWO HIGHS ANOTHER WEAK COLD FRONT WILL SLIP THROUGH THE OHIO VALLEY AND INTO EAST KENTUCKY MONDAY NIGHT INTO TUESDAY MORNING. DRIER AIR WILL PRESS SOUTH DEEPER INTO KENTUCKY DURING THE DAY TUESDAY AND INTO WEDNESDAY. ANOTHER COOL AREA OF HIGH PRESSURE THEN DESCENDS THROUGH THE GREAT LAKES AND SETTLES INTO THE OHIO VALLEY ON THURSDAY WITH A LIKELY DRY FRONT AT ITS LEADING EDGE. THIS HIGH THEN DRIFTS TO THE EAST BEFORE STARTING TO MODERATE LATER FRIDAY AND INTO THE DAY SATURDAY. ALTHOUGH NONE OF THESE HIGHS WILL PARK DIRECTLY OVER EAST KENTUCKY...THEY SHOULD BE STRONG ENOUGH TO KEEP ANY THREAT OF SHOWERS TO A MINIMUM. THE CR GRID LOAD PROVIDED A GOOD START TO THE FORECAST FOR THE EXTENDED...THOUGH DID ADJUST THE POPS A TAD TOWARD MORE OF A DIURNAL TREND EACH DAY AND ALSO TO GO A BIT DRIER LATTER IN THE PERIOD. DID TWEAK THE LOW TEMPERATURE GRIDS A BIT EACH NIGHT TO REFLECT SOME MINOR RIDGE AND VALLEY DIFFERENCES THAT WILL PROBABLY BE LARGEST ON THURSDAY AND FRIDAY NIGHTS. && .AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON) ISSUED AT 147 PM EDT SAT SEP 13 2014 IFR TO MVFR CIGS CONTINUE ACROSS MUCH OF EASTERN KY AS A UPPER LEVEL DISTURBANCE PASSES TO OUR NORTH. HIGH PRESSURE AND AN AREA OF DRYING ARE NOW STARTING TO MOVE IN ACROSS THE NW PART OF THE STATE...AND SHOULD SLOWLY WORK IT/S WAY INTO EASTERN KY DURING THE AFTERNOON/EVENING. CIGS WILL WORK THEIR WAY TO VFR BEFORE DISSIPATING...FIRST AT KSYM AND THEN LAST AT KSJS. WINDS SHOULD GENERALLY UNDER 10 KNOTS. GIVEN THE AMOUNT OF DRYING AND SUBSIDENCE MOVING INTO THE REGION...DON/T EXPECT FOG OR DRIZZLE TO BE MUCH OF AN ISSUE TONIGHT. THE LATEST NAM GUIDANCE IS POINTING AT THE POTENTIAL OF A LOW STRATUS DECK SETTING UP IF NOTHING ELSE...BUT EVEN THEN...EXPECT COVERAGE TO BE LIMITED. AS SUCH...ONLY MENTIONED SCT MVFR DECK AT THIS TIME BETWEEN 3 AND 14Z. BY TOMORROW...DRY AIR WILL PREVAIL AT ALL THE TAF SITES...WITH SOUNDINGS SHOWING SOME DIURNALLY DRIVEN VFR CU CLOUDS...BUT OTHERWISE BENIGN CONDITIONS. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...JMW LONG TERM...GREIF AVIATION...JMW

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