Issued by NWS Jackson, KY
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000 FXUS63 KJKL 210755 AFDJKL AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 255 AM EST SAT NOV 21 2009 .SHORT TERM.../TODAY THROUGH MONDAY/...UPDATED MODELS SOLUTIONS ARE IN REASONABLE AGREEMENT WITH EVOLUTION OF UPPER AIR PATTERN. WEAK SHORT WAVE PASSING THROUGH THE GREAT LAKES REGION WILL CONTINUE TO TRACK EASTWARD. A MORE SIGNIFICANT LOW PASSING THROUGH TX WILL TAKE AIM AT EASTERN KENTUCKY...PASSING THROUGH AS AN OPEN WAVE BY LATE SUNDAY OR SUNDAY NIGHT. MODEL TRENDS HAVE BEEN SLOWER AND WEAKER WITH THIS FEATURE WITH RESPECT TO OUR WEATHER. THIS SYSTEM PULLS OFF TO THE NORTHEAST BY THE END OF THE PERIOD. AT THE SFC...LOW PRESSURE CENTER OVER THE GULF MORPHS INTO NOTHING MORE THAN AN INVERTED TROUGH OVER OUR AREA IN RESPONSE TO OPENING WAVE TRAVERSING THE TN VALLEY REGION SUNDAY. FOR ISC GRIDS...LEANED MORE TOWARDS THE NAM FOR THE FIRST 24 HOURS...THEREAFTER MOVING CLOSER TO A BLEND OF THE GFS AND ECMWF SOLUTIONS FOR THE REMAINDER OF THE PERIOD. THESE LATEST TRENDS HAVE A SIGNIFICANT AFFECT ON SENSIBLE WEATHER... PARTICULARLY WITH RESPECT TO POPS AND PRECIP. IN GENERAL HAD TO TREND LOWER WITH POPS THROUGH THE PERIOD...AND DECREASE QPF TOTALS. OTHERWISE...ONLY MADE SOME TWEAKS TO ELEMENTS TO COME INTO LINE WITH LATEST THOUGHTS. .LONG TERM.../MONDAY NIGHT THROUGH FRIDAY/...UPDATED MODELS HAVE BEEN ALL OVER THE BOARD WITH RESPECTIVE SFC SOLUTIONS. HOWEVER...MODELS CONTINUE TO SHOW DECENT AGREEMENT WITH OVERALL UPPER LEVEL PATTERN EVOLUTION. WEAK SHORT WAVE ENERGY TRACKS QUICKLY THROUGH THE OHIO VALLEY REGION MONDAY NIGHT...JUST AS A MORE POTENT LOW PRESSURE SYSTEM DROPS OUT OF THE INTERMOUNTAIN REGION INTO THE PLAINS. THIS SYSTEM MOVING OUT OF THE PLAINS WILL BE OUR NEXT WEATHER MAKER...MOST LIKELY AFFECTING OUR AREA FROM MID WEEK THROUGH THE THANKSGIVING HOLIDAY. THE ECMWF HAS A SLOWER...MORE SOUTHERLY TRACK THAN THE GFS AND SWINGS A FRONTAL BOUNDARY THROUGH OUR AREA LATE WEDNESDAY...ABOUT 24 HOURS SLOWER THAN EARLIER RUNS. THE GFS HAS TRENDED SLOWER AS WELL...WITH THIS FRONT MOVING THROUGH OUR AREA TUESDAY NIGHT INTO WED MORNING...OR ABOUT 12 HOURS SLOWER. MADE APPROPRIATE CHANGES TO THE FORECAST TO ACCOUNT FOR THESE LATEST TRENDS...THOUGH CONFIDENCE IS OVERALL SCENARIO OF EVENTS IS LOW AT BEST. MOST INTERESTINGLY...BOTH THE GFS AND ECMWF SHOW A SIGNIFICANT BAND OF WRAP AROUND MOISTURE AFFECTING OUR AREA BEHIND THE MAIN SYSTEMS DEPARTURE ON THANKSGIVING. THE GFS COLUMN PROFILES SUPPORT THE POTENTIAL OF SOME SNOW LATE THURSDAY INTO THURSDAY NIGHT. HOWEVER...THE ECMWF IS QUITE A BIT WARMER. ATTM PREFERRED THE WARMER ECMWF SOLUTION AND WILL LEAVE ANY MENTION OF THE WHITE STUFF OUT OF THE FORECAST. && .AVIATION.../06Z TO 06Z/ ASIDE FROM THE POSSIBILITY OF LATE NIGHT MVFR TO IFR FOG IN THE DEEPER VALLEYS TOWARD DAWN...VFR CONDITIONS WILL BE THE RULE THROUGH THE TAF PERIOD AS HIGH PRESSURE KEEPS THE AREA CLEAR BELOW 12K FEET. JUST A SCT TO BKN LAYER OF HIGH CLOUDS OF VARYING THICKNESS IS EXPECTED THROUGH SATURDAY MORNING. HAVE KEPT THE HIGHEST THREAT OF IFR FOG IN THE SME TAF WITH A LONGER PERIOD OF MVRF FOG EXPECTED... COMPARED TO LOZ...WHILE JKL WILL NOT SEE ANY FOG. WINDS WILL BE LIGHT...GENERALLY FROM THE NORTHEAST THROUGH THE PERIOD. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...RAY LONG TERM...RAY AVIATION...GREIF