134 FXUS64 KHUN 280330 AAB AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 930 PM CST WED NOV 27 2013 .UPDATE... NO CHANGES NEEDED && .DISCUSSION... QUITE A DIFFERENT WX PICTURE COMPARED TO LAST NIGHT ATTM...WITH CLR SKIES AND UNSEASONABLY COLD CONDS/TEMPS PREVAILING ACROSS THE AREA. STRONG AREA OF HIGH PRESSURE OUT OF THE SRN PLAINS CONTINUES TO SETTLE INTO THE LOWER MS/TN VALLEY REGIONS...WITH FRIGID ARCTIC AIR STREAMING INTO THE AREA FROM THE NNW. TONIGHT IS DEFINITELY GOING TO BE VERY COLD...WITH OVERNIGHT TEMPS FALLING INTO THE TEENS FOR MOST AREAS. ONE BIT OF GOOD NEWS AT LEAST IS THAT SFC WINDS HAVE WEAKENED SIG...WHICH SHOULD HELP OFFSET WIND CHILLS FROM LOWERING MUCH PAST TEMP TRENDS. THE ONGOING FORECAST LOOKS TO HAVE THIS FRIGID PATTERN HANDLED WELL...AND NO UPDATES ARE NEEDED AT THIS POINT. STAY WARM. 09 && .AVIATION... /ISSUED 507 PM CST WED NOV 27 2013/ FOR 00Z TAFS...WITH A STRONG AREA OF HIGH PRESSURE OUT OF THE SRN PLAINS/LOWER MS VALLEY BUILDING EWD INTO THE AREA...VFR CONDS ARE XPCTED THROUGH THE TAF PERIOD. 09 && .PREV DISCUSSION... /ISSUED 305 PM CST WED NOV 27 2013/ CURRENT WATER VAPOR SATELLITE ANIMATION CONFIRMS THE PRESENCE OF AN AMPLIFIED MID-LEVEL LONGWAVE TROUGH EXTENDING FROM HUDSON BAY SOUTHWARD INTO THE SOUTHERN APPALACHIANS THIS AFTERNOON. SHORT TERM MODEL GUIDANCE IS IN GENERAL AGREEMENT IN FORECASTING THIS TROUGH TO DEEPEN FURTHER TONIGHT AS IT PHASES WITH THE SOUTHERN STREAM SHORTWAVE TROUGH WHICH TRACKED ACROSS THE CENTRAL GULF COAST LAST NIGHT...WITH THE CONGLOMERATE TROUGH AXIS EXPECTED TO LIFT NORTHEASTWARD INTO NEW ENGLAND BY 12Z THURSDAY. A BENIGN NORTHWEST FLOW ALOFT WILL PERSIST ACROSS NORTHERN ALABAMA/SOUTHERN MIDDLE TENNESSEE TONIGHT AND TOMORROW IN THE WAKE OF THE DEPARTING TROUGH...WHILE THE CENTER OF AN ARCTIC SURFACE HIGH SLOWLY TRANSLATES NORTHEASTWARD FROM THE SOUTHERN PLAINS. THE STRONG SOUTHWARD ADVECTION OF COLD/DRY AIR TODAY WILL SET THE STAGE FOR IDEAL RADIATIONAL COOLING TONIGHT AS LINGERING CLOUD COVER DISSIPATES AND THE PBL DECOUPLES WITH THE APPROACH OF THE SURFACE HIGH. A CONSENSUS OF MODEL PROGS OF SURFACE DEWPOINTS WOULD ARGUE FOR A NIGHT OF NEAR RECORD COLD TEMPERATURES...AS DEWPOINTS WILL LIKELY BE IN THE 10-15 DEGREE RANGE -- WITH PERHAPS EVEN SOME SINGLE DIGIT DEWPOINTS. AT THIS TIME...WILL STAY ON THE COOL SIDE OF MOS GUIDANCE WITH LOWS GENERALLY IN THE 17-21 RANGE...ALTHOUGH SOME READINGS IN THE LOWER TEENS MAY BE POSSIBLE IN THE SHELTERED VALLEYS OF NORTHEAST ALABAMA AND SOUTHERN TENNESSEE. A STRONG LOW-LEVEL INVERSION NOTED IN FORECAST SOUNDING WILL ENSURE TEMPERATURES IN ELEVATED TERRAIN AROUND 5 DEGREES WARMER THAN IN ADJACENT VALLEYS. LITTLE CHANGE IN THE OVERALL SYNOPTIC PATTERN IS EXPECTED TOMORROW... WITH A SUNNY BUT COOL THANKSGIVING DAY ANTICIPATED REGION-WIDE. WINDS WILL BE LIGHT/VARIABLE...WITH THE CENTER OF A BROAD SURFACE RIDGE EXPECTED TO REMAIN OVER THE REGION. HIGH-LEVEL CIRROFORM CLOUD COVER MAY BEGIN TO INCREASE VERY LATE ON THURSDAY...BUT MORE LIKELY ON THURSDAY EVENING...AS A WEAK 500-MB WAVE -- CURRENTLY ACROSS THE SOUTHWESTERN U.S. -- TRACKS EASTWARD. DESPITE LIGHT/VARIABLE WINDS AND DEWPOINTS IN THE 13-18 DEGREE RANGE...THE INCREASE IN HIGH-LEVEL CLOUD COVER SHOULD PREVENT FULL RADIATIONAL COOLING FROM BEING REALIZED WITH LOWS GENERALLY IN THE LOWER/MID 20S. CLOUDS MAY DECREASE EARLY ON FRIDAY AS THE INITIAL WAVE ALOFT TRACKS EASTWARD... BUT ANOTHER/STRONGER SYSTEM PUSHING ACROSS THE CENTRAL PLAINS AND INTO THE OHIO VALLEY MAY BRING A RETURN OF THICKER HIGH-LEVEL CLOUDS FROM LATE FRIDAY THROUGH FRIDAY NIGHT. ONCE AGAIN...LOWS ON FRIDAY NIGHT SHOULD BE 2-4 DEGREES WARMER DUE TO HIGH CLOUDS AND THE ONSET OF LIGHT EAST-SOUTHEAST RETURN FLOW. PARTLY CLOUDY SKIES AND WARMER TEMPERATURES ARE ANTICIPATED ON SATURDAY...AS SOUTHEASTERLY WINDS SHOULD INCREASE JUST A BIT IN RESPONSE TO A SURFACE LOW TRACKING EASTWARD ALONG THE U.S.-CANADIAN BORDER. HOWEVER...A MORE PRONOUNCED WARMING/MOISTENING TREND WILL BEGIN ON SUNDAY...AS IT APPEARS AS IF FLOW ALOFT WILL FINALLY BACK TO THE WEST-SOUTHWEST IN ADVANCE OF AN ELONGATED MID-LEVEL SHEAR AXIS EXTENDING FROM THE CENTRAL ROCKIES INTO THE SOUTHWESTERN U.S. THIS FEATURE IS PROGGED TO MOVE EASTWARD ACROSS THE SOUTHERN PLAINS ON SUNDAY AND MAY PHASE WITH A STRONGER NORTHERN STREAM SYSTEM DIGGING SOUTHEASTWARD ACROSS THE NORTHERN PLAINS. A GRADUALLY DEEPENING SURFACE CYCLONE ACCOMPANYING THIS SYSTEM IS EXPECTED TO SHIFT EASTWARD FROM TEXAS INTO THE LOWER MISSISSIPPI VALLEY BY MONDAY MORNING. LIGHT PRECIPITATION WILL LIKELY OVERSPREAD THE REGION FROM THE WEST ON SUNDAY NIGHT...AS LARGE SCALE ASCENT INCREASES WITH THE APPROACH OF THE MID-LEVEL WAVE AND PWAT VALUES INCREASE TO AROUND 1 INCH. HOWEVER...WITH THE TRACK OF THE SURFACE LOW PLACING THE ENTIRE FORECAST AREA IN THE COOL SECTOR AND WEAK MID-LEVEL LAPSE RATES NOTED ON FORECAST SOUNDINGS...WE WILL ONLY MENTION RAIN IN THE FORECAST AT THIS TIME. BRIEF MID-LEVEL RIDGING WILL RESULT IN LOWER RAIN CHANCES ON MONDAY NIGHT/TUESDAY. HOWEVER...WINDS ALOFT WILL BACK TO THE SOUTHWEST ONCE AGAIN TUESDAY NIGHT AS A STRONG UPPER LOW MOVES ACROSS THE NORTHERN ROCKIES. SEVERAL SOUTHERN STREAM DISTURBANCES MAY IMPACT THE REGION DURING THIS PERIOD...WITH PERHAPS A MORE WIDESPREAD THREAT FOR RAIN DEVELOPING ON WEDNESDAY. 70/DD && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.