183 FXUS64 KHUN 010206 AAB AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 906 PM CDT SUN MAR 31 2013 .UPDATE... REMOVED THUNDER FOR THE REST OF THE EVENING. MADE OTHER ADJUSTMENTS (MAINLY DOWNWARD) CONCERNING RAIN CHANCES AND OVERNIGHT LOW TEMPS. LEFT PATCHY FOG WORDING IN FOR NOW. && .DISCUSSION... INTERESTINGLY ENOUGH...SHOWERS THAT AFFECTED THE REGION EARLIER WERE LACKING IN THUNDER...NOT ENTIRELY UNUSUAL BUT A NICER CHANGE TO WHAT LATE MARCH NORMALLY OFFERS. THE LAST OF THE SHOWERS WERE MOVING TO THE ENE...EXTENDING FROM LAMAR/FAYETTE COUNTIES OF WESTERN AL...TO ACROSS THE SOUTHERN HALF OF CULLMAN COUNTY...AND EAST OF ROME GA. IN DEEPER MOISTURE AND HIGHER INSTABILITY WELL TO THE SOUTH...THUNDER WAS NOTED MAINLY FROM NEAR MONTGOMERY AND EAST/SOUTH. A COLD FRONT WAS SLOWLY MOVING ACROSS THIS REGION...NOW JUST SOUTH OF THE TENNESSEE RIVER. COOLER AIR NORTH OF THIS BOUNDARY WILL FILTER ACROSS THE VALLEY DURING THE OVERNIGHT...WITH COOLER OVERNIGHT LOWS IN COMPARISON TO THE LAST FEW NIGHTS. SKIES WERE ALSO CLEARING AS THE SLIGHTLY DRIER AIR SEEPS SOUTHWARD...AND SYSTEM'S UPPER SUPPORT MOVES FURTHER TO THE EAST. THE DECREASE IN CLOUD COVER...ALONG WITH LIGHT WINDS...AND PLENTY OF RESIDUAL MOISTURE FROM THE RECENT BOUT OF RAIN...ALL ELEVATE A RISK OF FOG DEVELOPMENT. IN THE FIRST UPDATE TO REMOVE THUNDER... HAVE LEFT PATCHY FOG WORDING IN AS IS. HOWEVER...MAY HAVE TO RAISE THAT TO AREA OR WIDESPREAD COVERAGE. IF FOG...ESPECIALLY DENSE FOG BECOMES MORE THAN PATCHY IN COVERAGE...A DENSE FOG ADVISORY MAY BE NEEDED FOR THE OVERNIGHT. WE WILL EVALUATE THIS AND MAKE UPDATES AS CONDITIONS WARRANT. RSB && .AVIATION... /ISSUED 635 PM CDT SUN MAR 31 2013/ FOR 00Z TAFS... SHOWER ACTIVITY WILL GRADUALLY WIND DOWN THIS EVENING...AS A SERIES OF COLD FRONTS MOVE SOUTHWARD ACROSS THE REGION. WEST WINDS IN THE 3-7KT RANGE WILL BECOME NORTHERLY THIS EVENING...THEN LIGHT/VARIABLE AFTER MIDNIGHT. RESIDUAL MOISTURE AND LIGHT WINDS WILL BE CONDUCIVE FOR THE FORMATION OF FOG...AND LOCAL VISIBILITY RESTRICTIONS INTO THE IFR RANGE. FOG THAT FORMS SHOULD BURN AWAY SHORTLY AFTER DAYBREAK... WITH VFR WEATHER RETURNING BY THE LATE MORNING. RSB && .PREV DISCUSSION... /ISSUED 334 PM CDT SUN MAR 31 2013/ OFF AND ON RAINFALL ACROSS THE TENNESSEE VALLEY HAS MADE FOR A MILD AND FAIRLY DREARY EASTER SUNDAY. JUST A FEW PEEKS OF SUN ALLOWED LOCATIONS TO FINALLY HIT THE MID 60S...WITH THE HIGHEST TEMPS IN THE CWA THIS AFTERNOON AROUND 68 DEGREES OCCURRING IN NW AL. WITH BETTER FORCING AND DEWPOINTS CLIMBING INTO THE LOW 60S TO OUR SOUTHWEST THIS AFTERNOON...THEY HAVE SEEN THE STRONGER CONVECTIVE DEVELOPMENT. AS WAS MENTIONED YESTERDAY IN THE FORECAST...OUR COOLER TEMPERATURES HELPED PREVENT MUCH CONVECTION THIS FAR N. THROUGH THE EVENING HOURS...SOME SHOWERS AND PERHAPS A RUMBLE OF THUNDER OR TWO CAN BE EXPECTED TO CONTINUE TRACKING ACROSS THE CWA. OUR FIRST SHORTWAVE/COLD FRONT WILL PUSH PRECIP SE OF THE CWA LATE THIS EVENING BUT LEAVE SIGNIFICANT SFC MOISTURE IN ITS WAKE FOR OVERNIGHT. THE CONCERN FOR THIS PERIOD WHEN DOING THE FORECAST YESTERDAY WAS WHETHER THE BACK EDGE OF CLOUDS WOULD CLEAR TO ALLOW FOR NOCTURNAL COOLING...AND WHETHER WINDS WOULD GO CALM TO PREVENT MIXING IN THE BL. ATTM AM ANTICIPATING WINDS TO BECOME CALM LATE THIS EVENING AND ALLOW FOR FOG TO START DEVELOPING EVEN WITH SOME LINGERING CLOUDS. THE 850MB THERMAL TROF AXIS IS EXPECTED TO STALL AS IT SLIDES TOWARD OUR AREA AND COULD THEREFORE KEEP SOME CLOUDS OVER THE CWA. NORMALLY THIS WOULD SIGNIFICANTLY HAMPER OUR POTENTIAL FOR FOG DEVELOPMENT...BUT COLD ADVECTION NW OF OUR CWA LAST NIGHT WAS ENOUGH TO PRODUCE THE FOG EVEN WITHOUT CLEARING SKIES. HAVE THEREFORE KEPT THE FOG MENTION IN THE FORECAST AND INCLUDED DENSE FOG WORDING IN NW AL AFTER MIDNIGHT WHERE CLOUD COVER HAS A BETTER CHANCE OF THINNING. WILL NOT ISSUE A DENSE FOG ADVISORY ATTM DUE TO LINGERING UNCERTAINTIES ABOUT THE IMPACTS OF CLOUD COVER...BUT WILL ALLOW THE EVENING SHIFT TO MONITOR TRENDS AND UPDATE ACCORDINGLY. A FEW MORE BREAKS IN THE CLOUD COVER TOMORROW SHOULD HELP TEMPERATURES WARM NICELY INTO THE UPPER 60S BEFORE OUR NEXT COLD FRONT ARRIVES. THE POTENTIAL FOR SOME LIGHT RAIN WITH FROPA CONTINUES TO BE HIGHLY QUESTIONABLE AS THE LIFT AND MOISTURE ASSOCIATED WITH THIS FRONT IS LIMITED...BUT THE BIGGER STORY WILL DEFINITELY BE THE COLD AIR ARRIVING WITH THE FRONT. STRONG COLD ADVECTION COMBINED WITH DAYTIME CLOUDS SHOULD BRING US BACK INTO THE 50S FOR HIGHS/30S FOR LOWS REGIME WE HAVE BEEN SO USED TO RECENTLY. DUE TO SURPRISING CONTINUITY IN THE GLOBAL FORECAST MODELS...NOT MUCH HAS CHANGED IN THE EXTENDED FORECAST OTHER THAN FINE TUNING OF PRECIP TIMING. FOR MID TO LATE WEEK...A STRONGER SHORTWAVE WILL DEEPEN OFF THE LEE OF THE ROCKIES AND THEN PHASE WITH A SHORTWAVE TRACKING ACROSS THE US/CANADIAN BORDER. OUR BEST RAIN CHANCES WILL OCCUR THURS INTO FRIDAY AS THE WAVE SLIDES ACROSS THE SOUTHEAST AND DEVELOPS A SFC FEATURE IN THE NE GULF. DO NOT NORMALLY PUT LIKELY POPS THAT FAR IN THE EXTENDED...BUT CONFIDENCE IS FAIRLY HIGH SINCE BOTH THE GFS AND ECMWF HAVE BEEN ZEROING IN ON THIS PERIOD FOR THE PAST COUPLE DAYS OF RUNS. IF TEMPERATURES WERE AS COLD AS THEY HAVE BEEN...THIS STORM TRACK WOULD BE AN IDEAL SETUP FOR A GOOD WINTER WEATHER EVENT ACROSS THE TENNESSEE VALLEY BUT WE WILL BE WARM ENOUGH TO AVOID THAT FATE. THAT BEING SAID...HAVE STILL UNDERCUT THE MEX GUIDANCE IN THE EXTENDED TO ACCOUNT FOR IMPACTS FROM PRECIP AND CLOUD COVER...ESPECIALLY DURING THE DAY ON THURSDAY. CCC && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.