000 FXUS64 KHUN 100308 AAB AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 908 PM CST THU FEB 9 2012 .UPDATE... EVENING FCST UPDATE. MINOR UPDATES TO GRIDS AND UPDATED AFM/PFM ALREADY SENT. && .DISCUSSION... QUIET WEATHER PREVAILS ACROSS THE TN VALLEY THIS EVENING WITH FAIRLY WEAK HIGH PRESSURE CENTERED OVER MID TN. TWO AREAS OF CLOUDS ARE NOTED ON SATELLITE...MAINLY CIRRUS TO THE SOUTH ASSOCIATED WITH AN UPPER-LEVEL JET STREAK AND CENTRAL PACIFIC MOISTURE FETCH...AND STRATUS OVER THE PLAINS AND MID-MS VALLEY ASSOCIATED WITH AN APPROACHING SHORTWAVE. TEMPS DROPPED LIKE A ROCK EARLIER THIS EVENING UNDER MOSTLY CLEAR SKIES...BUT THE FALL HAS BEEN STUNTED BY INCREASING CIRRUS OVER THE LAST 1-2 HRS. AREA TEMPS ARE GENERALLY IN THE MID-UPPER 30S WITH A FEW WARM AND COLD OUTLIERS. LOW LEVEL MOISTURE AND UPGLIDE WILL DEVELOP OVER THE LOWER MS VALLEY OVERNIGHT IN RESPONSE TO THE PLAINS SHORTWAVE...RESULTING IN AN INCREASE IN STRATUS ESPECIALLY TO THE WEST. INCREASING MID AND UPPER- LEVEL MOISTURE WILL BE THE SOURCE OF MOST OF THE CLOUDINESS OVER THE TN VALLEY...SO A FCST OF INCREASING CLOUDS STILL LOOKS GOOD THOUGH SOME DETAILS WILL BE TWEAKED IN THE GRIDS. TEMPS AND TRENDS WILL BE INCONSISTENT AND DEPENDENT ON RADIATIONAL COOLING...BUT BELIEVE THE CURRENT LOW FCST AROUND 30 STILL LOOKS GOOD FOR MOST OF THE AREA. WILL MAKE A FEW MINOR ADJUSTMENTS TO MATCH THIS FCST THINKING...BUT NO MAJOR CHANGES ARE REQUIRED ATTM. BCC && .AVIATION... /ISSUED 527 PM CST THU FEB 9 2012/ FOR 00Z TAFS...VFR CONDITIONS ARE GENERALLY EXPECTED THRU APPROXIMATELY 18Z/10...BUT MAY PERSIST THRU 00Z/11. CLOUDS WILL INCREASE AND LOWER THRU THE TAF PERIOD. BY TMRW AFTN...LT SHRA CANNOT BE RULED OUT AS CEILINGS DECREASE TO LOW-END VFR. HOWEVER TIMING AND EXACT VIS IMPACTS OF ANY SHRA REMAIN UNCERTAIN...SO WILL ONLY HAVE VCSH IN TAFS FOR NOW. BCC && .PREV DISCUSSION... /ISSUED 331 PM CST THU FEB 9 2012/ HIGH PRESSURE BUILDING INTO THE SOUTHEAST TODAY HAS KEPT CONDITIONS QUIET BUT PARTLY TO MOSTLY CLOUDY ACROSS THE AREA. THE CLOUD COVER OVER THE TN VALLEY HELPED KEEP TEMPERATURES FROM CLIMBING BEYOND THE MID TO UPPER 40S...RANGING FROM 5 TO 10 DEGREES BELOW CLIMATE NORMALS FOR EARLY FEBRUARY. UNFORTUNATELY...THIS CHILLY TREND IS EXPECTED TO SIMPLY STRENGTHEN OVER THE NEXT SEVERAL DAYS. A STRONG COLD FRONT ACROSS THE US/CANADIAN BORDER TODAY WILL FINALLY GET SOME UPPER LEVEL SUPPORT TOMORROW AS SOME PVA HELPS DEEPEN THE MAIN LONGWAVE TROF OVER CANADA AND BRING THE MAIN AXIS ACROSS THE GREAT LAKES AND TOWARD THE NORTHERN APPALACHIANS BY SATURDAY MORNING. THIS WILL SYNC UP WITH A WEAKER SHORTWAVE JUST PUSHING EASTWARD OFF THE SOUTHERN ROCKIES...COMBINING SOME MARGINAL MOISTURE AND VERY COLD TEMPERATURES AND PUSHING THEM ACROSS THE SOUTHEAST FRIDAY AND SATURDAY. TEMPERATURES ARE EXPECTED TO REMAIN WARM ENOUGH FRIDAY TO KEEP MOST PRECIP IN THE FORM OF RAIN...UNTIL THE MAIN SHOT OF COLD AIR ARRIVES JUST AFTER MIDNIGHT. MODEL SOUNDING INDICATE THAT TEMPERATURES SHOULD BEGIN TO DROP BELOW FREEZING ACROSS THE CWA BETWEEN MIDNIGHT AND 3AM FRIDAY NIGHT/SATURDAY MORNING. MOISTURE IS EXPECTED TO QUICKLY DECREASE AND BECOME SHALLOW BEHIND THE DEPARTING FRONT...BUT THE MODELS ALSO INDICATE THERE SHOULD BE A PERIOD WHERE THE TOP OF THE COLUMN IS COLD ENOUGH TO SUPPORT CRYSTAL DEVELOPMENT (ARND -10C). HAVE THEREFORE INCLUDED A MIX AND CHANGEOVER TO LIGHT SNOW/FLURRIES FOR VERY EARLY SATURDAY MORNING. FLURRIES WILL THEN LIKELY LINGER FOR THE MORNING IN TN/NW AL WITH A TYPICAL SETUP OF NW FLOW BEHIND THE SYSTEM INTERACTING WITH THE TERRAIN. VERY CHILLY TEMPERATURES ARE THEN EXPECTED FOR THE WEEKEND...AS HAS BEEN WELL ADVERTISED IN THE FORECAST FOR THE PAST SEVERAL DAYS. DID DROP THE FCST HIGHS FOR THE WEEKEND A DEGREE OR TWO TO GO MORE IN LINE WITH THE MAV AND ONLY BRINGING SAT HIGHS INTO THE UPPER 30S. OVERNIGHT TEMPS FOR THE WEEKEND WILL BE QUITE COLD WITH 20S AND POSSIBLY TEENS ANTICIPATED FOR THE HIGHER TERRAIN. MORE SUNSHINE ON SUNDAY SHOULD HELP TEMPS RECOVER SLIGHTLY INTO THE LOWER 40S. MONDAY SHOULD WARM UP A BIT MORE WITH THE RETURN OF SOUTHERLY FLOW...BUT CLOUD COVER AHEAD OF ANOTHER SYSTEM WILL LIMIT IS SIGNIFICANT WARMING TREND. TEMPERATURES MAY DIP TO NEAR FREEZING AGAIN MONDAY NIGHT...WITH PROFILES SUGGESTING THE POTENTIAL FOR ANOTHER ROUND OF FROZEN PRECIP. CONSIDERING THIS IS 5 DAYS OUT...THE GFS IS SHOWING A STRONGER WARM NOSE THAN THE ECMWF FOR THE PERIOD...AND THE MODELS HAVE BEEN STRUGGLING WITH THE EXTENDED FORECAST...HAVE KEPT ALL PRECIP AS RAIN FOR THAT PERIOD. BUT FUTURE SHIFTS WILL NEED TO MONITOR THIS SITUATION FOR THE POTENTIAL OF RAIN TRANSITIONING TO SLEET OR SNOW LATE MONDAY INTO TUESDAY. BEYOND THAT...TEMPERATURES SHOULD BEGIN TO PUSH BACK TO NEAR/ABOVE NORMAL VALUES AS A RIDGE BUILDS AGAIN ACROSS THE SOUTHEAST AND SOUTHERLY FLOW INCREASES ON THURSDAY AHEAD OF YET ANOTHER LOW PRESSURE SYSTEM. THIS MORE ACTIVE FORECAST PERIOD ALL STEMS FROM THE ANTICIPATED BREAKDOWN OF SEVERAL BLOCKING EPISODES OVER THE N HEMISPHERE IN THE NEXT WEEK...WHICH MAY BE PART OF WHY THE MODELS ARE STRUGGLING WITH THE FORECAST A BIT. TRENDED MUCH OF THIS FCST TOWARD THE ECMWF SOLN WHICH USUALLY SHOWS MORE RUN TO RUN CONSISTENCY IN CHANGING PATTERNS SUCH AS THIS. CCC && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.