Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 100512 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 112 AM EDT THU JUL 10 2014 .UPDATE... ISSUED AT 1023 PM EDT WED JUL 9 2014 UPDATED SKY GRIDS TO BETTER REFLECT CURRENT CONDITIONS AS WELL AS THE LATEST GUIDANCE FOR WHAT IS EXPECTED THROUGHOUT THE REMAINDER OF TONIGHT AND INTO THE DAY TOMORROW. ALSO LOADED IN THE LATEST OBSERVATIONAL DATA TO MAKE SURE THAT TEMPS...DEW POINTS...AND WINDS WERE ON TRACK WITH THE ONGOING FORECAST. NO OTHER CHANGES WERE NEEDED AT THIS TIME. HOWEVER...STILL CONTINUING TO MONITOR THE FOG SITUATION AS WE HEAD INTO THE OVERNIGHT HOURS WITH DEW POINTS SLOWLY INCREASING AND NEAR SURFACE INVERSIONS SETTING UP. WILL MAKE UPDATES AS NEEDED. UPDATE ISSUED AT 802 PM EDT WED JUL 9 2014 AS WAS NOTED IN THE LAST UPDATE...THE CURRENT DRY AIRMASS MOVING IN HAS DROPPED DEW POINTS QUITE SUBSTANTIALLY. AS SUCH...WAS A LITTLE LEARY ON THE EXTENT OF FOG DEVELOPMENT ACROSS MUCH OF THE REGION...ESPECIALLY SINCE SHOWERS WERE VERY ISOLATED IN NATURE DURING THE AFTERNOON AND MANY AREAS HAVE HAD AMPLE OPPORTUNITY FOR ANY LINGERING MOISTURE /FROM MORNING SHOWERS/ TO MIX OUT. WITH LOWER DEW POINTS IN THE UPPER 50S TO AROUND 60 NOW TAKING HOLD ACROSS THE REGION...AND MORE UPPER 50S JUST UPSTREAM AS WELL...WILL BE INTERESTED TO SEE IF THIS WILL HAMPER FOG DEVELOPMENT ALL TOGETHER. THAT BEING SAID...BELIEVE THE VALLEY REGIONS WILL HAVE THE BEST OPPORTUNITY FOR SEEING FOG DEVELOPMENT OVERNIGHT...AS THESE AREAS TEND TO SEE COOLER TEMPERATURES OVERNIGHT AND HOLD MORE MOISTURE NEAR CREEKS AND STREAMS. WITH THIS UPDATE...CONFINED FOG TO THE BROAD VALLEYS ACROSS EASTERN KY...WITH ONLY PATCHY AND AREAS OF FOG MENTIONED. AS WE HEAD INTO THE NIGHT...WILL LIKELY REASSESS BASED ON HOW CONDITIONS SET UP AND UPDATE AS NEEDED. UPDATE ISSUED AT 730 PM EDT WED JUL 9 2014 THE NEXT FEW HOURS OF THE FORECAST SEEMS TO BE WELL ON TRACK. DEW POINTS ARE CONTINUING TO DROP ACROSS THE REGION AS DRIER AIR USHERS IN. AS SUCH...CLOUDS ARE SHOWING A DECREASING TREND...AND WILL CONTINUE TO DO SO WITH LOSS OF DIURNAL HEATING. A LITTLE CONCERNED ABOUT THE EXTENT OF FOG OVERNIGHT. WITH DEW POINTS ALREADY THIS LOW...THERE IS SOME DOUBT AS TO WHETHER OR NOT THERE WILL BE ENOUGH MOISTURE LEFT DURING THE OVERNIGHT HOURS TO PRODUCE FOG. EVEN LATEST NAM AND GFS FORECAST SOUNDINGS ARE SHOWING A SCATTERED MID LEVEL CLOUD DECK BUT OTHERWISE FAIRLY DRY AIR BELOW. WILL LIKELY MAKE ADJUSTMENTS TO THE OVERNIGHT DEW POINTS AND EXPECTED FOG COVERAGE. && .SHORT TERM...(THIS EVENING THROUGH THURSDAY NIGHT) ISSUED AT 257 PM EDT WED JUL 9 2014 DRIER AIR CONTINUES TO TRY TO ADVECT INTO THE REGION AS A COLD FRONT VERY SLOWLY SAGS SOUTHWARD THROUGH SOUTHEAST KENTUCKY. DEW POINTS HAVE DROPPED INTO THE 50S ALONG I-64 BUT REMAIN IN THE MID TO UPPER 60S SOUTH OF THE FRONT. AN ISOLATED SHOWER OR STORM WILL REMAIN POSSIBLE OVER EXTREME SOUTHEAST KENTUCKY INTO THE EARLY EVENING HOURS. FOG WILL THEN BECOME THE PRIMARY CONCERN OVERNIGHT. WHILE FOG IS A GOOD BET OVER SOUTHEAST KENTUCKY...THE DRIER AIR FILTERING INTO OUR NORTHERN COUNTIES MAY LIMIT IT/S EXTENT. TEMPERATURES WILL RANGE FROM NEAR 60 IN THE NORTH TO MID 60S IN THE MORE HUMID AIR MASS OVER SOUTHEAST KENTUCKY. THE FRONT WILL REMAIN VERY CLOSE TO THE VIRGINIA AND TENNESSEE BORDER AS IT WASHES OUT ON THURSDAY AND AN ISOLATED SHOWER OR STORM WILL BE POSSIBLE AGAIN FOR THESE AREAS THURSDAY AFTERNOON. OTHERWISE...ANOTHER CU FIELD WILL DEVELOP WITH DAYTIME HEATING AND THEN DISSIPATE THURSDAY NIGHT. HIGHS ON THURSDAY WILL RETURN TO THE MID 80S WITH LOWS THURSDAY NIGHT IN THE LOW TO MID 60S. .LONG TERM...(FRIDAY THROUGH WEDNESDAY) ISSUED AT 359 PM EDT WED JUL 9 2014 A DRY AIR MASS BY SUMMERTIME STANDARDS SHOULD BE IN PLACE AS THE PERIOD STARTS...AS SURFACE HIGH PRESSURE PASSES BY TO OUR NORTH UNDER WEAK NW FLOW ALOFT BEHIND A NE CONUS UPPER TROUGH. MODELS SHOW GEOPOTENTIAL HEIGHTS BRIEFLY BUILDING OVER THE REGION AS WE HEAD INTO THE WEEKEND. ALONG WITH A DRY AIR MASS...THIS SUPPORTS WARMING TEMPS FOR FRIDAY. MOISTURE WILL BEGIN TO INCREASE DURING THE WEEKEND... WHILE A SHORTWAVE TROUGH PASSES EASTWARD NORTH OF THE OHIO RIVER...AND A LARGE SCALE TROUGH DEEPENS OVER THE NORTH CENTRAL AND NORTHEAST CONUS. THE PASSING SHORTWAVE AND INCREASING MOISTURE COULD BE ENOUGH TO ALLOW SOME SHOWERS OR STORMS IN OUR NORTHERN COUNTIES ON SATURDAY AFTERNOON OR EVENING...BUT THE BETTER POP WILL BE TO OUR NORTH. USED POPS IN CHANCE CATEGORY ON SUNDAY AS GEOPOTENTIAL HEIGHTS FALL AND MOISTURE CONTINUES TO INCREASE. WHILE THE GFS AND ECMWF DISAGREE SOMEWHAT ON THE DETAILS...THEY DO AGREE ON THE OVERALL PATTERN...AND SHOW THE SURFACE COLD FRONT ASSOCIATED WITH THE UPPER TROUGH ARRIVING ON MONDAY NIGHT. HAVE USED THE HIGHEST POPS AHEAD OF THE FRONT...BUT JUST SHY OF LIKELY CATEGORY DUE TO LACK OF CONFIDENCE IN DETAILS. MODELS SHOW THE FRONT STALLING TO OUR SOUTH TUESDAY AND WEDNESDAY...BUT CLOSE ENOUGH AND WITH ENOUGH OVERRIDING MOISTURE THAT LOW POPS WERE STILL WARRANTED IN THE FORECAST. && .AVIATION...
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(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT) ISSUED AT 110 AM EDT THU JUL 10 2014 THIS IS A VERY DIFFICULT FORECAST DUE TO THE VARIABILITY OF THE MOISTURE SPREAD ACROSS THE AREA TONIGHT. MOST OF THE VALLEYS HAVE DECOUPLED ALREADY...SO EXPECT TO SEE SOME FOG FORM IN THE VALLEYS...ESPECIALLY IN AREAS SOUTH OF JACKSON. THE DRIER AIR AT THE SURFACE WAS ONLY ABLE TO MAKE ITS WAY INTO THE NORTHWEST THIRD OF EASTERN KENTUCKY. NORMALLY...IN THIS SCENARIO...THE STATIONS WITH THE HIGHER DEWPOINTS SHOULD BE SEEING SOME VALLY FOG WITH VLIFR CONDITIONS AFTER 9Z. STATIONS LIKE JKL...WILL NOT SEE FOG FORM OVERHEARD...HOWEVER SOME MAY FORM IN THE VALLEYS BELOW AND THE LIFT AS THE HEATING STARTS UP. THIS LIFTED FOG THEN MAY MOVE ACROSS THE AIRFIELD. IT IS MORE LIKELY TO MOVE ACROSS THE ASOS THAN THE RUNWAY. SME AND SJS HAD MUCH LOWER TEMPERATURE/DEWPOINT SPREADS...SO MADE THE CONDITIONS WORSE THERE. ONCE THE FOG BURNS OFF...EXPECT VFR FOR THE REST OF THE DAY.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...ABE LONG TERM...HAL AVIATION...JJ

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