000 FXUS64 KHUN 160822 AFDHUN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HUNTSVILLE AL 322 AM CDT TUE SEP 16 2008 .SHORT TERM...THROUGH THURSDAY... IT FINALLY FEELS LIKE FALL ACROSS THE CENTRAL TENN VALLEY THIS MORNING. DESPITE A PERSISTENT CANOPY OF CIRROSTRATUS...TEMPS HAVE FALLEN INTO THE UPPER 50S/LOWER 60S ACROSS A GOOD PORTION OF THE HUN CWFA. DEWPOINTS ACROSS THE AREA CONTINUE TO FALL SLOWLY AND ARE NOW IN THE MID 50S...AS DRY AIR ADVECTION CONTINUES BEHIND THE RECENT COLD FRONT...WHICH HAS NOW PUSHED SWD TO THE GULF COAST. THE BAND OF CIRROSTRATUS IS DUE TO A PLUME OF SUBTROPICAL MOISTURE WITH ORIGINS ALONG THE WRN MEXICO COAST. AN UPPER LVL TROUGH MARKS THE WRN EDGE OF THIS PLUME...AND THE TROUGH AXIS IS MOVING THROUGH THE MEMPHIS AREA ATTM. UPPER TROUGH AXIS IS PROGGED TO SLIDE THROUGH THE HUN CWFA TODAY... ALBEIT VERY SLOWLY. ENOUGH OF THE REGION MAY GET INTO NORTHERLY FLOW ALOFT THAT SKIES MAY BEGIN TO CLEAR OUT BY THE AFTN...BUT SKY COVER LOOKS TO BE AT LEAST PTLY CLOUDY FOR MOST OF THE DAY. PERSISTENT LOW-LVL COOL AIR ADVECTION WILL KEEP TEMPS FROM REACHING MUCH BEYOND THE 80 DEGREE MARK PER MOS CONSENSUS AND HAVE ACCEPTED THESE VALUES...THOUGH IT IS WORTH NOTING THAT MOS TENDS TO OVERDO HIGHS IN SUCH CONDITIONS. BY TONIGHT...SKIES SHOULD BE CLEARING AND WINDS SHOULD DECOUPLE ENOUGH FOR A GOOD RADIATIONAL COOLING NIGHT...AND HAVE TRENDED 2-4 DEGREES BELOW MOS CONSENSUS FOR MUCH OF THE AREA. THE NAM BECOMES MUCH MORE AGGRESSIVE WITH MOISTURE RETURN AND CONVERGENCE ALONG THE I-59 CORRIDOR BY WEDNESDAY...WHICH GAINS SOME UPPER LEVEL SUPPORT WITH THE LAGGING UPPER TROUGH AXIS. THERE IS SOME SUPPORT FOR THIS FROM THE ECMWF AND SREF MEAN...BUT MOST OF IT IS CONFINED TO AREAS WELL SE OF HERE. BELIEVE THE PCPN IN THIS CASE IS A BIT OVERDONE GIVEN THE DOMINANT DEEP NORTHERLY FLOW...BUT IT WILL BE WORTH WATCHING. MODEL CONSENSUS DOES DRY THINGS OUT MORE CONSISTENTLY BY THURSDAY. THROUGH THIS PERIOD...HIGHS WILL MODERATE SLIGHTLY BUT SHOULD STILL BE AT OR JUST BELOW SEASONAL AVERAGES... WHILE MODIFIED PERSISTENCE WILL BE THE RULE FOR LOWS. .LONG TERM...FRIDAY THROUGH TUESDAY... DAYS 4-7 ARE SOMEWHAT MUDDLED WITH A POTENTIAL WEAK CUTOFF LOW. THE LOW IS INITIALLY PROGGED TO EVOLVE OVER THE CENTRAL PLAINS THEN MIGRATE EWD...EVENTUALLY ENDING UP IN THE OHIO VALLEY AND SETTING UP A PERSISTENT SHEAR AXIS ACROSS THE CENTRAL TENN VALLEY TOWARDS THE END OF THE FCST PD. MODEL CONSISTENCY AND AGREEMENT REGARDING THIS FEATURE HAVE NOT VERY GOOD...BUT FOR NOW FEEL THE 00Z/16 ECMWF SOLN IS MOST REALISTIC. THIS WOULD PRBLY MEAN A DRY FCST FOR SOME PART OF THE WEEKEND...BUT AM NOT COMPLETELY CONVINCED BY THE ECMWF QPF-FREE SOLN EITHER GIVEN THE UNSETTLED UPPER FLOW. TEND TO BELIEVE THIS WOULD LEND ITSELF TO SOME SORT OF MOISTURE ADVECTION AND POSSIBLY LT PRECIP...BUT TIMING IS EXTREMELY PROBLEMATIC WITH SUCH WEAK FEATURES AND MODEL INCONSISTENCY. SO WILL CONTINUE WITH A DRY FCST FOR THE TIME BEING AND GO WITH A CLIMO/GFSX MOS BLEND FOR TEMPS. && .PRELIMINARY POINT TEMPS/POPS... HUNTSVILLE 79 56 81 58 83 / 10 0 0 0 10 SHOALS 78 56 81 57 84 / 10 0 0 0 10 CULLMAN 78 57 80 59 81 / 10 0 0 0 10 FAYETTEVILLE 78 56 80 58 82 / 10 0 0 0 10 ALBERTVILLE 78 57 80 58 82 / 10 0 10 10 10 FORT PAYNE 79 56 81 56 84 / 10 0 10 10 10 && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ BCC