FXUS64 KHUN 062329 AAA AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 529 PM CST THU MAR 6 2014 .UPDATE... FOR 00Z TAFS && .DISCUSSION... /ISSUED 304 PM CST THU MAR 6 2014/ THE 21Z SURFACE ANALYSIS INDICATED THAT A LARGE AREA OF LIGHT TO MODERATE RAIN WAS MOVING NORTH INTO THE FORECAST AREA FROM CENTRAL ALABAMA. THE PRECIP AREA WAS ROTATING NORTHWARD AROUND THE EASTERN PERIPHERY OF THE UPPER LOW ACROSS WEST CENTRAL MISSISSIPPI. HAVE BEEN A BIT CONCERNED ABOUT POTENTIAL FOR A BRIEF MIX WITH SLEET ON THE LEADING EDGE OF THE PRECIP...BUT WILL JUST STAY WITH A COLD RAIN. AGREE THAT THE BUFR SOUNDING DATA IN VICINITY OF NORTHEAST ALABAMA AROUND CHATTANOOGA TENNESSEE...WAS INDICATING THAT THE LAYER FROM 850 MILLIBARS-SURFACE WOULD BE A LITTLE TOO WARM FOR ENOUGH DENDRITIC ICE GROWTH TO PRODUCE MUCH IN THE WAY OF SLEET. HAVE CONTINUED WITH THE HIGHER PRECIP CHANCES ACROSS THE FORECAST AREA TONIGHT...WHICH SHOULD BE MORE IN LINE WITH NAM PRECIP GUIDANCE. THE SHORT TERM MODELS SHIFT THE PRECIP AREA ASSOCIATED WITH THE UPPER LOW TO THE SOUTHEAST OF THE FORECAST AREA. THIS SOLUTION IS GENERALLY ACCEPTED AND WILL ONLY CARRY A LINGERING SLIGHT CHANCE POP FOR NORTHEAST ALABAMA FOR THE MORNING HOURS ON FRIDAY. WEAK HIGH PRESSURE IS PROGGED BY THE MODELS TO SHIFT EASTWARD INTO THE FORECAST AREA DURING THE DAY ON FRIDAY...WITH A QUICK RETURN FLOW AROUND TO THE SOUTH EXPECTED BY SHORTLY AFTER 00Z SATURDAY ACROSS THE AREA. WITH ABUNDANT SUNSHINE EXPECTED ON FRIDAY...HAVE SLIGHTLY WARMED HIGH TEMPS ACROSS THE FORECAST AREA MORE IN LINE WITH GUIDANCE. THE MODELS QUICKLY SHIFT THE HIGH PRESSURE RIDGE EASTWARD AND OFF THE ATLANTIC COAST BY 12Z SATURDAY...WITH A ZONAL MID AND UPPER LEVEL FLOW IN PLACE ACROSS THE TENNESSEE VALLEY REGION. THE NEXT UPPER LEVEL SYSTEM TO AFFECT THE REGION WILL TAKE SHAPE IN THE SOUTHERN ROCKY MOUNTAIN REGION BY 12Z SATURDAY. THIS UPPER TROUGH WILL SHIFT EASTWARD INTO THE SOUTHERN PLAINS INTO THE LOWER OHIO VALLEY REGION DURING THE DAY ON SATURDAY. A SURFACE COLD FRONT IS PROGGED BY THE MODELS TO MOVE SOUTHEAST FROM THE SOUTHERN PLAINS/MISSOURI VALLEY REGION...INTO THE LOWER OHIO VALLEY BY 18Z SATURDAY...THEN INTO MIDDLE TENNESSEE BY 00Z SUNDAY. HAVE CONTINUED WITH AT LEAST A SLIGHT CHANCE POP MAINLY WEST OF I-65 BY SATURDAY EVENING...AND THEN ACROSS THE REST OF THE FORECAST AREA OVERNIGHT SATURDAY NIGHT AND INTO SUNDAY MORNING. LOW LEVEL MOISTURE AND UPPER SUPPORT WILL BE LACKING WITH THIS SYSTEM...BUT THERE SHOULD STILL BE ENOUGH MOISTURE/INSTABILITY FOR A FEW SCATTERED/WIDELY SCATTERED SHOWERS. WILL CONTINUE WITH A SLIGHT CHANCE OF SHOWERS AS THE COLD FRONT IS EXPECTED TO SINK SOUTH OF THE FORECAST AREA BY 18Z SUNDAY. HAVE SPLIT THE DIFFERENCE BETWEEN THE COOLER GFS AND SLIGHTLY WARMER ECMWF TEMPS FOR AFTERNOON HIGHS. THE MODELS DISSIPATE THE FRONTAL BOUNDARY INTO CENTRAL ALABAMA BY LATE SUNDAY. THE FOCUS THEN WILL TURN TO WEST TEXAS...AS THE MODELS LATCH ON TO A DEVELOPING UPPER LOW AT 500 MILLIBARS. LOW TO MID LEVEL MOISTURE IS PROGGED BY THE MODELS TO BEGIN DEVELOPING AND MOVING NORTHWARD OUT OF THE SOUTHERN GULF OF MEXICO BY 00Z TUESDAY. THE ECMWF AND GFS MODELS...TO VARYING DEGREES...MOVE SCATTERED SHOWERS NORTHEAST THROUGH LOUISIANA AND INTO MISSISSIPPI INITIALLY BY 12Z TUESDAY. THE ECMWF MODEL IS MORE PRONOUNCED WITH THE MOISTURE TRANSPORT NORTHEASTWARD WITH THIS SYSTEM AND FOR NOW HAVE GONE WITH A COMPROMISE INVOLVING PRECIP CHANCES FOR THE FORECAST AREA ON TUESDAY AFTERNOON THROUGH WEDNESDAY. HAVE INCREASED PRECIP CHANCES HIGHER INTO THE CHANCE CATEGORY FOR THE FORECAST AREA ESPECIALLY FROM TUESDAY NIGHT AND INTO WEDNESDAY. INVOLVING TEMPS ON MONDAY AND TUESDAY...HAVE WARMED TEMPS MORE TOWARD ECMWF/GFS TEMP GUIDANCE. THE ECMWF MODEL SOLUTION HAS THE UPPER LOW LIFTING MORE NORTHWARD INTO FAR EASTERN ARKANSAS BY 12Z WEDNESDAY. THIS IS IN COMPARISON TO THE GFS MODEL...WHICH OPENS THE UPPER LOW ON TUESDAY ACROSS THE SOUTHERN GULF AND PROGRESSIVELY DEVELOPS AND MOVES A SURFACE LOW OFF OF THE ATLANTIC COAST. WILL LINGER PRECIP IN ACROSS THE FORECAST AREA LONGER INTO WEDNESDAY...WHICH MAY BE MORE IN LINE WITH THE ECMWF MODEL SOLUTION. HAVE TRENDED TOWARD A COMPROMISE SOLUTION FOR THE FORECAST AREA INVOLVING TEMPS FROM WEDNESDAY THROUGH THURSDAY. DUE TO THE EXPECTED EASTWARD PUSH OF THE STORM SYSTEM AWAY FROM THE FORECAST AREA ON THURSDAY...HAVE REMOVED THE MENTION OF PRECIP ACROSS THE AREA. TT && .AVIATION... FOR 00Z TAFS... MVFR CONDS WILL PREVAIL FOR MUCH OF THE NEXT 12 HOURS AS LIGHT RAIN OVERSPREADS THE TERMINALS FROM THE SOUTH/EAST AS AN UPPER LOW PUSHES ACROSS THE REGION. THOUGH CEILING HEIGHTS WILL HOVER BETWEEN 3000-4000FT, A LOWER BKN015 DECK IS POSSIBLE IN THE HEAVIER RAIN THROUGH MIDNIGHT. AS THE UPPER LOW SHIFTS EASTWARD BY DAYBREAK, WINDS WILL TURN TO THE NORTH, INCREASING TO ARND 10KTS TOMORROW AFTN. SKIES WILL CLEAR FROM WEST TO EAST WITH ONLY A FEW LOW CLOUDS REMAINING BY 07/18Z. 12 && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Thu, 06 Mar 2014 23:30:54 +0000
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