Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 201543 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 1143 AM EDT WED AUG 20 2014 .UPDATE... ISSUED AT 1143 AM EDT WED AUG 20 2014 A RATHER CHALLENGING FORECAST THIS MORNING. TAIL END OF FRONTAL ZONE...BOUNDARY IS EVIDENT ACROSS THE MID WEST THIS MORNING AND WILL PLAY A MAJOR ROLE IN OUR WEATHER OVER THE NEXT SEVERAL DAYS. BUILDING RIDGE OF HIGH PRESSURE ALOFT AND TO OUR WEST WILL FORCE THIS BOUNDARY TO THE EAST OVER THE NEXT 24 HOURS. THIS BOUNDARY WILL BECOME INCREASINGLY ALIGNED WITH MID AND UPPER LEVEL FLOW PATTERNS AND BECOME STATIONARY ACROSS THE MID OHIO VALLEY REGION. THEREAFTER IT SERVES AS A FOCUS FOR CONVECTION AND THE OCCASIONAL CONVECTIVE COMPLEX OF STORMS. ATTM IT APPEARS AT LEAST PART OF OUR AREA WILL FEEL THE EFFECTS OF WEAK IMPULSES OF ENERGY RIDING OVER AND DROPPING DOWN ALONG THE EAST SIDE OF THE RIDGE AXIS. IMMEDIATE QUESTION IS WILL CURRENT UPSTREAM ACTIVITY OVER IA/IL MANAGE TO MAKE IT INTO OUR AREA. MOST LIKELY ANSWER LIES WITHIN THE SYNOPTIC PATTERN THAT IS TAKING SHAPE...BEST DESCRIBED AS AN ALMOST IDEAL MCS GENERATOR. MODELS SEEM TO HAVE PICKED UP ON THIS AS WELL... DEPICTING THE SOURCE OF MOISTURE/ENERGY...NAMELY BOUNDARY LAYER H925 TO H850 FLOW INTO THESE STORM COMPLEXES WEAKENING THROUGH THE DAY DUE TO DIURNAL MIXING...THE INCREASING AGAIN AT NIGHT. THESE COMPLEXES ONCE GENERATED THEN RIDE SOUTHEAST ALONG THE BOUNDARY. THAT BEING SAID EXPECT THE CURRENT ACTIVITY ACROSS IA/IL TO WEAKEN A BIT THROUGH THE DAY. BUT CONFIDENCE IS LOW THAT ACTIVITY WILL COME TO A COMPLETE END. MOST RECENT RUNS OF THE RAP AND HRRR SUPPORT THIS LINE OF THOUGHT AND REGIONAL SATELLITE DOES SHOW A DEFINITE WARMING TREND TO CLOUD TOPS ATTM. DECIDED TO TRIM POPS DOWN JUST A BIT THROUGH THE AFTERNOON BUT LEAVING ENOUGH TO TO ACCOUNT FOR ISOLD TO SCATTERED CONVECTION ASSOCIATED WITH DIURNAL HEATING AND ACTIVITY THAT MAY FIRE ALONG ANY RESIDUAL OUTFLOW BOUNDARIES. PREVIOUS FORECAST HAS POPS INCREASING AGAIN TONIGHT WHICH IS IN LINE WITH CURRENT THOUGHTS AS WELL...ESPECIALLY WITH THE SURFACE BOUNDARY SHIFTING TO THE EAST ACROSS OUR AREA. ALSO TWEAKED HOURLY TEMPS AND WINDS TO BRING THE GRIDS IN LINE WITH LATEST HOURLY OBS. FINALLY FRESHENED UP ZONES TO REMOVE MORNING FOG WORDING. UPDATE ISSUED AT 800 AM EDT WED AUG 20 2014 SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL EXIT SOUTHEASTERN KENTUCKY IN THE NEXT ONE TO TWO HOURS. ONCE THESE STORMS CLEAR THE AREA...THERE MAY BE SOME ISOLATED TO SCATTERED CONVECTION RE- DEVELOPING ACROSS EASTERN KENTUCKY THIS AFTERNOON DURING PEAK HEATING. WILL STAY THE COURSE AND CONTINUE TO MENTION THE POPS...HOWEVER SOME OF THE GUIDANCE HAS TRENDED DRIER...AND GIVEN THE SUBSIDENCE FOLLOWING THE DEPARTING WAVE...WOULD NOT BE SURPRISED IF CONVECTION IS EVEN MORE ISOLATED. UPDATES HAVE BEEN SENT. && .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 357 AM EDT WED AUG 20 2014 A COMPLEX OF SHOWERS AND THUNDERSTORMS IS CURRENTLY SLIDING EAST ACROSS THE OHIO VALLEY ASSOCIATED WITH A PASSING SHORT WAVE TROUGH. THE MORE ORGANIZED PORTION OF THIS COMPLEX HAS BEEN CONFINED TO ALONG AND NORTH OF THE MOUNTAIN PARKWAY. THE HRRR MODEL HAS NOT BEEN HANDLING THIS FEATURE WELL THROUGH THE OVERNIGHT...OVERPLAYING THE DEVELOPMENT TO THE SOUTH THAT HAS BEEN WEAK IN REALITY...WHILE UNDERPLAYING WHERE CONVECTION HAS BEEN MORE ORGANIZED AND SUSTAINED. EXPECT THIS COMPLEX TO KEEP MOVING EAST...AFFECTING LOCATIONS ALONG AND NORTH OF THE MOUNTAIN PARKWAY FOR THE NEXT FEW HOURS...BEFORE EXITING THE AREA BY 12Z. THERE WILL BE SOME SUBSIDENCE FOLLOWING THIS DEPARTING SHORT WAVE FOR TODAY WORKING IN FROM WEST TO EAST...SO HAVE TRIMMED THE POPS BACK A BIT...PEAKING IN THE 20 TO 30 RANGE FOR MOST LOCATIONS DURING THE HOTTER PART OF THE DAY. HIGHS TODAY WILL RANGE FROM 85 TO 90 DEGREES. AS WE HEAD INTO TONIGHT...CONVECTION WILL BE ON THE DOWNWARD TREND THROUGH 06Z...BUT THEN LOOKS TO INCREASE BETWEEN 06 AND 12Z...AS ANOTHER SHORT WAVE TROUGH APPROACHES FROM THE NORTHWEST. POP CHANCES WILL CONTINUE TO INCREASE THROUGH THE DAY ON THURSDAY WITH HEATING AIDING THE MODEST FORCING FROM THE PASSING SHORT WAVE. HAVE MAINTAINED THE BETTER POPS IN THE NORTHEAST...AND LESSER VALUES IN THE SOUTHWEST...FURTHER REMOVED FROM THE BETTER FORCING. HIGHS WILL RETURN TO THE 85 TO 90 DEGREE RANGE IN THE SOUTHWEST...WITH MID 80S IN THE NORTHEAST...WHERE MORE PERSISTENT CLOUD COVER WILL RESIDE. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 335 AM EDT WED AUG 20 2014 THE EXTENDED PORTION OF THE FORECAST BEGINS ON THURSDAY NIGHT WITH A SLOWLY BUILDING RIDGE OVER THE CENTRAL CONUS AND DIGGING TROUGHS OVER THE NORTHWEST AND NORTHEAST. THIS GENERAL TREND CONTINUES THROUGH THE ENTIRE EXTENDED PERIOD. DURING THIS PERIOD...QUITE A FEW STRONG SHORTWAVES TRAVEL OVER THE BUILDING RIDGE IN THE CENTRAL PLAINS AND INTO THE OH VALLEY AND GREAT LAKES REGION. THE FIRST WAVE OF NOTE WILL BE THE SHORTWAVE MOVING THROUGH AT THE BEGINNING OF THE EXTENDED. AFTER THIS...THE PATTERN TURNS INTO A MORE MCS DRIVEN PATTERN FRIDAY THROUGH SUNDAY WITH ACTIVITY CENTERED AROUND WHAT THE DAYS CONVECTION BRINGS AND IS DIURNALLY AFFECTED. THROUGH THE PERIOD THE UPPER RIDGE SLOWLY WEAKENS AND DRIFTS EAST. CONCERNING THE MODELS DURING THE EXTENDED...THE GFS AND EURO LOOK TO BE RIGHT ON TRACK AND IN GOOD AGREEMENT. THOUGH...THE EURO LOOKS TO CUT OFF ANY CONVECTION BY THE END OF THE EXTENDED AS THE RIDGE AXIS SETS UP RIGHT OVER EASTERN KENTUCKY LEADING TO AN END TO ALL DIURNALLY DRIVEN CONVECTION AND DISPLACING THE TRACK OF THE MCS MORE TO THE NORTHEAST. BASED ON THE GOOD AGREEMENT...IT SEEMS TO BE A GOOD CONSENSUS TO STAY CLOSE TO THE SOLUTION OF THE ALL BLEND MODEL. THOUGH DEPENDING ON WHAT THE 00Z EURO DOES ON THE MONDAY AND TUESDAY TIME FRAME FOR THE RIDGE AXIS RIGHT OVER THE AREA...MAY DROP POPS BELOW THE ALL MODEL BLEND SOLUTION. WITH THE SOLUTION OF THE ALL MODEL BLEND...THE BEST CHANCE OF POPS WILL BE DURING THE FRIDAY THROUGH SUNDAY TIME FRAME AND LESS DURING THE MONDAY AND TUESDAY TIME FRAME WHERE THE RIDGE WILL BE OVER EASTERN KENTUCKY AND HAVE LEFT SLIGHT CHANCE MAINLY DURING THE AFTERNOON ON MONDAY AND TUESDAY. IN ADDITION TO THIS PATTERN...TEMPERATURES WILL BE ON THE INCREASE IN EARNEST AS SOME OF THE WARMEST WEATHER OF THE ENTIRE SUMMER WILL BEGIN TO SET IN FROM FRIDAY THROUGH THE REST OF THE EXTENDED. HIGH TEMPERATURES WILL SURPASS 90 DEGREES IN SOME AREAS OF EASTERN KENTUCKY AND HUMIDITY WILL BE ON THE INCREASE AS WELL. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING) ISSUED AT 815 AM EDT WED AUG 20 2014 SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL EXIT OFF TO THE SOUTHEAST IN THE NEXT HOUR OR TWO. IFR/LIFR FOG WILL LIFT OUT IN THE NEXT HOUR...WITH A RETURN TO VFR CONDITIONS THROUGH THE REST OF THE DAY. SOME ISOLATED TO SCATTERED CONVECTION WILL THREATEN AGAIN THIS AFTERNOON...BUT COVERAGE IS EXPECTED TO BE LIMITED ENOUGH TO ONLY MENTION VCTS FOR NOW. FOG WILL LIKELY RETURN AFTER 06Z TONIGHT...HOWEVER ANOTHER UPPER LEVEL DISTURBANCE WILL LIKELY APPROACH BETWEEN 06 AND 12Z...BRINGING IN ADDITIONAL CLOUD COVER AND ALSO RENEWING THE CONVECTIVE THREAT. THIS WILL LIKELY KEEP THE FOG FROM BECOMING TOO DENSE. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...GEOGERIAN LONG TERM...SHALLENBERGER AVIATION...GEOGERIAN

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