554 FXUS62 KTAE 171334 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 930 AM EDT WED MAR 17 2010 .SYNOPSIS... AT 9 AM EDT...SKIES WERE CLOUDY ACROSS THE REGION. LOCAL RADARS SHOWED WIDESPREAD LIGHT RAIN FALLING FROM A STRATIFORM ALTO DECK AND SPREADING NORTHEAST ACROSS THE NORTHEAST GULF AND FL PANHANDLE. TEMPS RANGED FROM MID 40S NORTH TO AROUND 50 AT THE COAST. 24 HR TEMP/DEW POINT COMPARISON INDICATES A SIGNIFICANT AIRMASS MODIFICATION...8-12 DEGREES WARMER/WETTER THAN SAME TIME YESTERDAY. WINDS WERE GENERALLY N/NW 3-8 MPH. AT UPPER LEVELS... THE LARGE SCALE CONUS PATTERN REMAINS AMPLIFIED HIGHLIGHTED BY A RIDGE OVER WRN STATES...AND TROUGHINESS ACROSS EASTERN HALF OF CONUS. THIS INCLUDES A 556MB LOW ON KS/MO BORDER AND A UPPER TROUGH OVER GULF OF MEX WITH A WEAK H5 558MB LOW CONTINUING TO ROTATE ALONG SW AL COAST. WATER VAPOR LOOP SHOWED ABUNDANT MID AND UPPER LEVEL MOISTURE ON THE N PERIPHERY OF THIS LOW. SEVERAL SHORTWAVES/H5 TROUGHS ARE ROTATING AROUND BOTH LOWS CONTRIBUTING TO A BROAD REGION OF LOWER HEIGHTS DOWN INTO THE GULF COAST STATES. LOOKING SOUTH... SBTRPCL JET CONTINUES TO ADVECT MOISTURE FROM THE PACIFIC NEWD TO CNTRL FLA. SO DRIEST AIR CONTINUES TO BE THAT WRAPPING S OF GULF LOW...NORTH OF SBTRPCL JET AND SOUTH OF SHORTWAVES. DURING THIS MORNING...ONE SHORT WAVE WAS PROPAGATING EASTWARD OVER THE E/CNTRL GULF COAST AND ANOTHER WAS DIVING SOUTHWARD OVER SE MO. THE FIRST SHORT WAVE WILL MOVE THROUGH OUR AREA REST OF THIS AFTN/EVE SHUNTING UPPER TROUGH EWD INTO THE NE GULF. THIS WILL PROVIDE PLENTY OF LIGHT RAIN UNTIL IT TAPERS OFF FROM WEST TO EAST THIS EVE AS THE SHORT WAVES MOVE TO OUR EAST. THE NEXT SHORTWAVE MOVES INTO THE NORTHERN GULF TONIGHT AND BEGIN TO PHASE WITH THE DEPARTING SHORTWAVE OVER THE EXTREME ERN FL. AS THESE LOWS ARE NEARLY CUT OFF FROM THE N JET...THIS PHASING WILL BE A SLOW PROCESS WITH TROUGH/LOW NOT OFF THE EAST COAST UNTIL THURS AFTN/EVE. THUS...THE GUIDANCE INDICATES THAT THERE WILL BE ENOUGH DEEP LAYER MOISTURE REMAINING INTO THURSDAY FOR A SMALL CHANCE OF SHOWERS. AS THE UPPER TROF LIFTS OUT...MID LEVEL HEIGHT RISES PUSH EASTWARD ACROSS THE NRN GULF WITH CLEARING FRIDAY INTO EARLY SATURDAY. THE RIDGE ADVANCES QUICKLY EASTWARD OFF THE EAST COAST ON SATURDAY WHILE THE NEXT STORM SYSTEM DEVELOPS OVER THE SRN PLAINS. THIS SETS UP A RETURN FLOW PATTERN OFF THE GULF BY LATE SAT ALLOWING FOR AN INCREASE IN DEEP LAYER MOISTURE OVERNIGHT SAT AND THRU SUN. THIS IS REFLECTED IN MODEL SOUNDINGS. I.E. GFS TAE WITH 0.91 INCH PWAT AT 18Z WED...HOVERING AROUND .07 AND .08 INCHES THRU 06Z FRI BEFORE SLOWLY DECREASING TO 1/2 INCH RANGE THRU SAT EVE BEFORE INCHING UP AGAIN INTO SUN. AT LOWER LEVELS... ANALYSIS SHOWED A TROUGH/DIFFUSE LOW EXTENDING FROM NORTH GA THROUGH THE FL WRN BIG BEND...WESTWARD INTO MS. THE COMBINATION OF ABOVE PASSING SHORTWAVE AND THIS TROUGH WAS PRODUCING INCREASING ISENTROPIC INDUCED MAINLY LIGHT RAIN. THIS TROUGH WILL MOVE SLOWLY EWD BY TONIGHT HELPING TO DRAG IN SOME DRIER AIR INTO THE LOWER LEVELS. STILL THE PASSING SHORTWAVE WILL ALLOW FOR SMALL CHANCE OF RAIN TONIGHT DECREASING FROM W-E. BY TOMORROW...RIDGING WILL BE PROMINENT ACROSS MUCH OF THE GULF OF MEXICO. A FAIRLY DEEP LOW IS PROGGED TO MIGRATE SSE THROUGH THE SRN PLAINS ON FRIDAY PUSHING THE RIDGE EASTWARD TOWARD THE ATLANTIC. AS THIS OCCURS...A BROADENING BELT OF MODESTLY STRONG SOUTHERLY FLOW WILL DEVELOP OFF THE GULF OF MEXICO. HOWEVER...A RELATIVELY DRY BOUNDARY LAYER OVER THE GULF OF MEXICO WILL TAKE TIME TO MODIFY AND THE LACK OF A RETURN FLOW WILL SUPPRESS ANY CHANCES OF LOCAL RAIN UNTIL ASSOCD COLD FRONT IS DRAGGED ESE ACROSS LOCAL AREA ON SUNDAY. && .SHORT TERM...(THIS AFTERNOON THROUGH TONIGHT) WITH THE LOW LEVEL TROUGH AND UPPER SHORTWAVES ACROSS LOCAL REGION... EXPECT CLOUDY AND RAINY PERIOD. PER WRF4K AND RUC...GREATEST COVERAGE AND BEST CHANCE FOR MODERATE RAIN WILL BE 15Z-19Z WITH RAIN THEN GRADUALLY DECREASING FROM W-E. WILL CONT WITH CATEGORICAL POPS REST OF TODAY BUT DECREASING FROM W-E THRU AFTN...AND A 20-40 PCT W-E POP GRADIENT TONIGHT. WILL INCREASE CLOUDS FORM M/CLOUDY TO CLOUDY. CLOUDS WILL MODERATE TEMPS...WITH HIGHS IN THE MID 50S WEST OF THE APALACHICOLA RIVER WHERE CLOUDS AND RAIN BEGAN EARLIEST...TO THE LOW 60S SE BIG BEND. MIN TEMPS TONIGHT WILL BE IN THE LOW-MID 40S. LOW STRATUS A GOOD BET TONIGHT ESPECIALLY EAST OF THE APALACHICOLA RIVER. WITH AREAS OF FOG LIKELY ESPECIALLY OVER GA ZONES LATE TONIGHT. THIS REFLECTED IN SREF PROGS. && .AVIATION...A WET DAY IS IN PROGRESS OVER OUR REGION. OVERCAST SKIES WITH RAIN WILL PREVAIL THROUGH MUCH OF THE TAF CYCLE. AN UPPER LOW OVER THE EASTERN GULF IS CREATING JUST ENOUGH LIFT TO SUPPORT WIDESPREAD SHOWER ACTIVITY OVER THE SOUTHEAST. CIGS WILL REMAIN MAINLY IN THE VFR CATEGORY THROUGH THE EARLY AFTERNOON AND SLOWLY BEGIN LOWERING TO IFR BY THIS EVENING. VSBYS WILL REMAIN VFR EXCEPT AROUND HEAVIER SHOWERS WHERE MVFR CONDITIONS CAN BE EXPECTED. CIGS WILL REMAIN LOW THROUGH THURSDAY MORNING WITH ISOLATED SHOWERS POSSIBLE. && .MARINE... OFFSHORE WINDS MAY APPROACH EXERCISE CAUTION LEVELS THIS AFTERNOON AND TONIGHT...BUT THEN SUBSIDE THURSDAY AND FRIDAY AS THE PRESSURE GRADIENT WEAKENS. FOR TODAY...WILL GO WITH NW AROUND 15 KNOTS WITH SEAS UP TO 4 FEET OFFSHORE. WINDS WILL SUBSIDE THURS AND FRI AS HIGH PRESSURE BUILDS EAST ACROSS THE NRN GULF REGION. WINDS WILL VEER TO ONSHORE AND BEGIN TO INCREASE ON SAT AHEAD OF NEXT FRONT. THIS FRONT WILL CROSS ON SUNDAY WITH WINDS INCREASING AND VEERING TO WEST AND THEN NW AND MAY APPROACH OR REACH ADVISORY LEVELS. && .FIRE WEATHER... NO FIRE WEATHER CONCERNS UNTIL POSSIBLY FRIDAY AND SATURDAY ACROSS PORTIONS OF NORTH FLORIDA. && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ BLOCK/AUSTIN