Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 291405 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 1005 AM EDT FRI AUG 29 2014 .UPDATE...
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ISSUED AT 1005 AM EDT FRI AUG 29 2014 VALLEY FOG HAS BURNED OFF ACROSS MOST LOCATIONS THIS MORNING...WITH JUST A TOUCH OF STRATUS LINGERING ALONG PORTIONS OF THE BIG SANDY AND CUMBERLAND RIVER BASINS. THE FORECAST IS ON TRACK...WITH HIGHS TOPPING OUT IN AND AROUND THE 90 DEGREE MARK FOR MOST LOCATIONS. A FAINT CU LINE SHOWN ON THE VISIBLE SATELLITE IMAGERY NEAR THE TN/KY BORDER REVEALS THE PRESENCE OF A QUASI-STATIONARY FRONTAL BOUNDARY...WHICH WILL BE LIFTING NORTH ACROSS EASTERN KENTUCKY TODAY AS A WARM FRONT. WILL MAINTAIN THE ISOLATED TO POSSIBLY SCATTERED CONVECTION ALREADY ADVERTISED. UPDATES HAVE BEEN SENT. UPDATE ISSUED AT 750 AM EDT FRI AUG 29 2014 HOURLY GRIDS HAVE BEEN FRESHENED UP A BIT BASED ON RECENT OBSERVATIONS. NO SIGNIFICANT CHANGES WERE MADE AT THIS TIME. LINGERING VALLEY FOG SHOULD LIFT AND DISSIPATE THROUGH AROUND 9 AM EDT. AN ISOLATED SHOWER OR THUNDERSTORM REMAINS POSSIBLE LATER THIS AFTERNOON AND EVENING. SOME OF THE RECENT MODEL GUIDANCE SUGGESTS THAT THE START OF SLIGHT CHANCE POPS MAY NEED TO BE PUSHED BACK A COUPLE OF HOURS.
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&& .SHORT TERM...
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(TODAY THROUGH SATURDAY) ISSUED AT 338 AM EDT FRI AUG 29 2014 AN UPPER LEVEL RIDGE OF HIGH PRESSURE WAS CENTERED OVER THE SOUTHEASTERN CONUS EARLY THIS MORNING AND EXTENDED NORTH AND NORTHWEST INTO THE APPALACHIANS AND THE OH VALLEY REGION. OVER THE MIDDLE OF THE COUNTRY...AN UPPER LEVEL TROUGH EXTENDED SOUTH THROUGH THE PLAINS STATES IN BETWEEN THE RIDGE CENTERED ACROSS THE SOUTHEASTERN CONUS AND ANOTHER RIDGE CENTERED TO THE SOUTHWEST OF CALIFORNIA. AT THE SFC HIGH PRESSURE WAS CENTERED OVER THE GREAT LAKES REGION. MEANWHILE...A BOUNDARY IS STALLED OUT FROM SOUTHEAST VA SOUTH INTO THE APPALACHIANS AND EAST TN AND THEN NORTHWEST TO LOW PRESSURE OVER THE PLAINS STATES. SOME PASSING CIRRUS AND MID LEVEL CLOUDS ARE MOVING ACROSS THE REGION AT THIS POINT AROUND THE RIDGE...ESPECIALLY THE FAR WEST AND THE NORTH. THIS HAS LEFT THE CUMBERLAND VALLEY WITH THE LEAST CLOUD COVER. DURING THE PERIOD...THE RIDGE IS EXPECTED TO REMAIN IN PLACE ACROSS THE SOUTHEASTERN CONUS...THOUGH THE AXIS OF THE RIDGE WILL DEPART TO THE EAST TODAY. THE SFC HIGH WILL MOVE EAST AS WELL. ALSO DURING THIS TIME...THE TROUGH OVER THE MIDDLE OF THE COUNTRY IS EXPECTED TO LIFT TOWARD THE GREAT LAKES WITH DEEP MOISTURE FROM THE GULF OF MEXICO INCREASING LATE IN THE PERIOD ON SOUTHWEST FLOW ALOFT. THE FLOW BETWEEN THE DEPARTED SFC HIGH AND THE SYSTEM MOVING INTO THE GREAT LAKES WILL HAVE A BIT OF A DOWNSLOPE COMPONENT EARLY ON SATURDAY. THROUGH SUNRISE AND TODAY...SOME AREAS OF VALLEY FOG HAVE FORMED OR ARE EXPECTED TO FORM BEFORE SUNRISE...AND MIGHT BECOME DENSE IN A COUPLE OF SPOTS. THE HARLAN AIRPORT KI35 HAS THE LOWEST VIS AT PRESENT. HOWEVER...ANY DENSE FOG SHOULD NOT BECOME WIDESPREAD WITH THE PASSING DEBRIS CLOUDS AND SOME MIXINESS WITH EAST TO SOUTHEAST FLOW AROUND THE WESTERN EDGE OF THE SFC HIGH. OTHERWISE...THE STALLED BOUNDARY WILL LIFT NORTH INTO THE REGION TODAY AS A WARM FRONT AND COMBINE WITH A WEAK APPROACHING DISTURBANCE IN SOUTHWEST FLOW AND DAYTIME HEATING TO YIELD GENERALLY ISOLATED TO POSSIBLY SCATTERED SHRA AND TSRA DURING THE AFTERNOON AND EVENING HOURS. THIS BOUNDARY WILL EXIT TO THE NORTH AND EAST TONIGHT AND INTO EARLY ON SATURDAY...LEAVING THE REGION IN THE WARM SECTOR. A WARM AIR MASS WILL REMAIN IN PLACE AND MOISTURE WILL INCREASE IN ALL LEVELS LATE IN THE PERIOD AS PW IS ANTICIPATED TO RISE TO AROUND 1.75 INCHES OR MORE IN MOST PLACES LATE. HOWEVER...FORCING FOR SAT REMAINS VERY LIMITED AND THE 0Z ECMWF AND 0Z GFS ACTUALLY HAVE SFC DEWPOINTS DECREASING FOR A WHILE ON SATURDAY POSSIBLY FROM THE DOWNSLOPE LOW LEVEL COMPONENT TO THE WINDS. IN ADDITION...THERE IS ALSO A MID LEVEL CAP FOR MUCH OF THE DAY AS WELL. ANY CONVECTION ON SAT SHOULD BE LATE IN THE DAY OR EARLY IN THE EVENING...AND THE BEST CHANCES APPEAR TO BE ACROSS THE SOUTHWEST AND WEST. TEMPERATURES ON SAT SHOULD APPROACH OR REACH 90 IN MANY LOCATIONS. .LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY) ISSUED AT 238 AM EDT FRI AUG 29 2014 MODELS HAVE BEEN FAIRLY CONSISTENT ON ADVERTISING A FAIRLY SHARP TROUGH PUSHING ACROSS THE OHIO RIVER VALLEY LATE SATURDAY NIGHT INTO SUNDAY MORNING. THUS...CONFIDENCE IS FAIRLY HIGH WE WILL SEE BETTER PRECIPITATION COVERAGE AROUND THIS PERIOD. WE MAY SEE A LULL FROM DIURNALLY DRIVEN CONVECTION ON SATURDAY THROUGH THE FIRST PART OF SATURDAY NIGHT. HOWEVER...SHOWERS AND STORMS WILL DEVELOP AND PUSH ACROSS THE AREA BY DAYBREAK. PW`S WILL CLIMB TO 1.8 TO 2 INCHES DURING THIS PERIOD..YIELDING THE THREAT FOR LOCALLY HEAVY RAINFALL AS THESE VALUES ARE NEAR THE 99TH PERCENTILE FOR LATE AUGUST. FORTUNATELY...STORM MOTION SHOULD BE SUFFICIENT TO PREVENT SLOW MOVING STORMS. MAIN CONCERN WILL REVOLVE AROUND ANY TRAINING STORMS WHICH MAY OCCUR. REGARDLESS...STORM WILL BE HEAVY RAINERS WITH GOOD POTENTIAL FOR PONDING ON ROADWAYS. SHORTWAVE TROUGH WILL BE ON THE WAY OUT BY LATE SUNDAY WITH PRECIPITATION CHANCES DECREASING. HOWEVER...STRONG RIDGING WILL DEVELOP OVER THE DEEP SOUTH...WITH EASTERN KENTUCKY RESIDING ON THE NORTH EDGE OF THIS HIGH PRESSURE DOME. THIS WILL KEEP THE AREA SUSCEPTIBLE TO WEAK SHORTWAVES AS THEY PROGRESS EASTWARD ALONG THE NORTHERN PERIPHERALS OF THIS HIGH PRESSURE AREA THROUGH THE WEEK. THUS...IT LOOKS LIKE THE WEATHER MAY STAY UNSETTLED WELL INTO NEXT WEEK AND PERHAPS BEYOND. THIS WARRANTS AT LEAST CHANCE POPS ALL THE WAY THROUGH THE END OF THE PERIOD. DOES NOT APPEAR WE WILL SEE ANY FORCING QUITE AS STRONG AS THIS WEEKEND...BUT ANY WEAK SHORTWAVE THIS TIME OF YEAR...COMBINED WITH DAYTIME INSTABILITY WOULD BE ENOUGH TO GENERATE ISOLATED TO SCATTERED STORMS. GIVEN THE TENDENCY FOR BETTER COVERAGE DURING THE AFTERNOONS/EVENINGS THIS TIME OF YEAR...PLAN TO GO WITH A DIURNAL TREND WITH POPS. TEMPERATURES WILL LIKELY STAY NEAR OR JUST ABOVE NORMAL THROUGH THE PERIOD AS HEAT AND HUMIDITY CONTINUE THROUGH THE NEXT WEEK.
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&& .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING) ISSUED AT 755 AM EDT FRI AUG 29 2014 LINGERING IFR OR WORSE VALLEY FOG WILL DISSIPATE BY AROUND 13Z FRIDAY...LEAVING PREVAILING VFR FOR MOST OF THE PERIOD. AT THE TAF SITES...MAINLY MVFR FOG IS ANTICIPATED INITIALLY AT LOZ AND SME. SJS HAS BEEN BOUNCING BETWEEN AIRPORT MINS AND VFR...BUT SHOULD ALSO SEE VFR BY 13Z. OTHERWISE...ONCE THE FOG DISSIPATES...ISOLATED THUNDERSTORMS ARE EXPECTED...GENERALLY AFTER 17Z...AS A WARM FRONT LIFTS NORTH TOWARD EASTERN KY. VIS AND OR CIGS COULD DROP BRIEFLY TO IFR OR LOWER IN ANY LOCATION THAT IS DIRECTLY AFFECTED BY ANY TSRA. SOME VALLEY LOCATIONS COULD EXPERIENCE MVFR OR LOWER FOG LATE IN THE PERIOD AS WELL. OF THE TAF SITES...KSJS MAY EXPERIENCE SOME OF THIS LIFTING INTO THE AREA. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...KAS AVIATION...JP

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