FXUS64 KHUN 090259 AAB AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 859 PM CST THU JAN 8 2015 .UPDATE... FOR MINOR TWEAKS TO THE TEMPERATURE, DEWPOINT, SKY COVER, AND WIND FORECAST. && .DISCUSSION... THE TN VALLEY ALONG WITH MOST OF THE CONUS IS UNDER THE INFLUENCE OF A HIGHLY AMPLIFIED TROUGH BRINGING THE POLAR JET ACROSS THE PLAINS, CORN BELT, OH RIVER VALLEY, MID ATLANTIC, AND NEW ENGLAND REGIONS. THE NW FLANK OF THIS TROUGH ACTUALLY STRETCHES WELL OVER THE ARCTIC (NORTHWEST OF BARROW, ALASKA!). WITH DEEP NW MID-UPPER FLOW OVERSPREADING MUCH OF THE REGION, A FEW MID-LEVEL SHORTWAVE TROUGHS ARE FLOWING FREELY ALONG THE POLAR JET. ONE OF THESE MID-LEVEL SHORTWAVE TROUGHS IS PUSHING A REINFORCING SFC COLD FRONT SOUTHEASTWARD TOWARDS THE TN VALLEY. THE FRONT IS CURRENTLY STRETCHING FROM E WI TO CENTRAL MO. AS THIS TROUGH APPROACHES, THE ARCTIC HIGH PRESSURE SYSTEM THAT BROUGHT THE REALLY COLD AIR YESTERDAY HAS SHIFTED OFF TO THE EAST LEAVING THE TN VALLEY ON ITS WESTERN FLANK. BECAUSE OF THE SFC HIGH EASTWARD MOVEMENT, SOUTHERLY SFC FLOW BEGAN THIS AFTERNOON AND CONTINUES TONIGHT. IR SAT AND CURRENT OBS BOTH INDICATE AN AREA OF CIRROSTRATUS/CIRRUS CLOUDS FROM THE SOUTHERN/WESTERN FLANK OF THE TROUGH OVERSPREADING THE TN VALLEY. AS A RESULT, MADE ADJUSTMENTS TO THE SKY COVER FORECAST--INCREASING TO PARTLY CLOUDY THROUGH MIDNIGHT. HOWEVER, THIS PARTICULAR AREA OF CS/CIRRUS CLOUDS SHOULD MOVE OFF TO THE SOUTHEAST EARLY IN THE MORNING. ADDITIONALLY, TEMPERATURES CONTINUE DROPPING TONIGHT, BUT NOT AS RAPIDLY AS ORIGINALLY FORECAST. THIS IS PROBABLY DUE TO THE COMBINATION OF THE ONCOMING CLOUD COVER AND SFC SOUTHERLY FLOW OF 5-10 MPH. SO, TWEAKED THE OVERNIGHT LOWS SLIGHTLY HIGHER, BUT KEPT DEWPOINTS LOWER THAN FORECAST DUE TO CURRENT TRENDS IN DEWPOINT TEMPERATURES (SINGLE DIGITS TO LOWER TEENS). DEWPOINTS WILL NOT RECOVER MUCH WITH THE REINFORCING SFC COLD FRONT COMING TOMORROW BTWN 14-16Z (8-10 AM CST). SL.77 && .AVIATION... /ISSUED 601 PM CST THU JAN 8 2015/ FOR 00Z TAFS...VFR CONDS WILL PREVAIL THRU THE VALID TAF PERIOD AT BOTH HSV/MSL...WITH SCT CI EXPECTED TO EXPAND/THICKEN INTO A BKN250 DECK BY MID-EVENING. SCT AC WILL ALSO DEVELOP BTWN 7-12 KFT THIS EVENING AND PERSIST UNTIL PASSAGE OF REINFORCING COLD FRONT FRIDAY MORNING. SWLY SFC WINDS OF 5-10 KNOTS WILL CONTINUE THRU THE NIGHT... WITH FLOW VEERING TO NNW AND INCREASING TO 9-11 KNOTS BTWN 09/14-16Z AS COLD FRONT CROSSES THE REGION. 70/DD && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Fri, 09 Jan 2015 03:00:02 +0000
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