NATIONAL WEATHER SERVICE MOBILE AL 501 AM CDT SAT MAR 15 2014 .SHORT TERM (TODAY AND TONIGHT)...MAIN CONCERN THROUGH TONIGHT WILL BE ONSET OF SHOWERS AND THUNDERSTORMS LATE TONIGHT AND EARLY SUNDAY MORNING IN RESPONSE TO MAIN UPPER LOW DIGGING OVER MUCH OF TEXAS LATE TONIGHT AND SUNDAY MORNING WITH A VIGOROUS LOW CENTER REFLECTING AT THE SFC TRACKING EASTWARD FROM THE LOWER MS RIVER VALLEY TO CENTRAL PARTS OF MS AND AL MOSTLY DURING THE DAY ON SUN. FURTHER SOUTH A WEAK SFC LOW IS ALSO REFLECTED OVER THE LOWER GULF PROGGED TO TRACK NORTHWARD TOWARDS THE CENTRAL GULF COAST LATER IN THE DAY ON SUN. OUT TO 24 HOURS THE LATEST 00Z GUIDANCE FROM THE GFS...NAM AND ECMWF ARE IN FAIR TO GOOD AGREEMENT WITH THE POSITION OF THE UPPER SYSTEM TO THE WEST AND THE VIGOROUS SFC LOW TRACKING INLAND OVER THE DEEP SOUTH COMBINED WITH THE DEVELOPMENT OF A 45 TO 55 KNOT H8 JET MAX POSITION OVER MUCH OF THE CWFA BY 12Z SUN. ALL THE MODEL GUIDANCE DEPICT THE LOW LEVEL JET SHIFTING EASTWARD OVER THE LOWER MS RIVER EARLY SUN MORNING SUGGESTING A FAIRLY ORGANIZED COMPLEX OF THUNDERSTORMS MOVING EASTWARD OUT OF MS AND LA SHORTLY AFTER 09Z SUN...RESULTING IN THE POSSIBILITY OF A FEW STRONG TO SEVERE THUNDERSTORMS MOVING OVER THE CWFA SHORTLY BEFORE SUNRISE....CONTINUING THROUGH THE LATE MORNING HOURS. CURRENT THINKING FROM THE STORM PREDICTION CENTER SUGGESTS THERE WILL BE A SLIGHT RISK FOR SEVERE THUNDERSTORM DEVELOPMENT OVER THE FORECAST AREA MOSTLY DURING THE MORNING HOURS ON SUN...BEGINNING SHORTLY BEFORE SUNRISE. DAMAGING WINDS...TORNADOES ALONG WITH PERIODS OF HEAVY RAIN AND FREQUENT LIGHTNING WILL ACCOMPANY SOME OF THE STRONGER THUNDERSTORMS BETWEEN 09Z AND 12Z SUN FOR MOST AREAS GENERALLY WEST OF THE I-65 CORRIDOR INCLUDING THE IMMEDIATE COAST MOSTLY WEST OF PENSACOLA FL. WILL CONTINUE TO MONITOR THIS DEVELOPING SITUATION CLOSELY TODAY AND MAKE FURTHER ADJUSTMENTS AS NEEDED. AS FOR TEMPS WITH A GOOD ONSHORE FLOW RESULTING IN BETTER WARM AIR ADVECTION TODAY AND TONIGHT WILL LEAN TOWARDS THE WARMER MAV OR MET GUIDANCE FOR TEMPS TODAY AND TONIGHT. /32 FOR SUNDAY THROUGH MONDAY NIGHT...A VIGOROUS AND POSITIVELY TILTED UPPER TROF OVER THE SOUTHERN/CENTRAL PLAINS ADVANCES EASTWARD THROUGH THE PERIOD...MOVING ACROSS THE REGION MONDAY INTO MONDAY NIGHT. THE GFS/ECMWF HAVE BEEN IN FAIR AGREEMENT ON AN ASSOCIATED SURFACE LOW MOVING ACROSS THE LOWER MISSISSIPPI RIVER VALLEY TO CENTRAL ALABAMA ON SUNDAY AND BRINGS A TRAILING COLD FRONT THROUGH THE FORECAST AREA SUNDAY NIGHT. AS THE UPPER TROF APPROACHES...A STRONG SERIES OF SHORTWAVES WILL BE EJECTING FROM THE TROF AND MOVING ACROSS THE FORECAST AREA. CONVECTION CONTINUES TO BE EXPECTED TO HAVE ORGANIZED INTO A SQUALL LINE WEST OF THE AREA EARLIER AND ADVANCED INTO THE WESTERN HALF OF THE AREA BY 12Z SUNDAY. THE CONVECTION CONTINUES EASTWARD SUNDAY MORNING AND IS EXPECTED TO EXIT THE EASTERN PORTION OF THE AREA BY MIDDAY OR SHORTLY THEREAFTER. THE STRENGTH OF THE 850 MB FLOW FOR SUNDAY MORNING WILL BE 40-50 KNOTS RESULTING IN HIGH HELICITY VALUES ALONG THE CONVECTIVE LINE. DEEP LAYER MOISTURE WILL BE HIGH AS WELL WITH PRECIPITABLE WATER VALUES OF 1.5-1.75 INCHES MAKING FOR HIGH PRECIPITATION RATES WITH THE ADVANCING LINE AND EXPECT THE SQUALL LINE TO BRING AROUND 1 INCH OF RAIN WHILE MOVING THROUGH WITH LOCALLY HIGHER AMOUNTS POSSIBLE. THE MAIN QUESTION CONTINUES TO BE WITH THE AMOUNT OF INSTABILITY WITH THE SQUALL LINE. THE GFS AND ECMWF MODEL SOUNDINGS CONTINUE TO SHOW LIMITED INSTABILITY ORIENTED WITH THE CONVECTIVE LINE WITH SURFACE BASED CAPES AS HIGH AS 400 J/KG. THIS IS EXPECTED TO BE UNDERDONE THOUGH AND PER COORDINATION WITH SPC...HIGHER INSTABILITY COULD BE PRESENT ESPECIALLY NEAR THE COAST. SPC HAS A SLIGHT RISK FOR THE SOUTHERN HALF OF THE AREA WHICH IS A GOOD BALANCE FOR THE POTENTIAL BETTER INSTABILITY WITH THE HIGH SHEAR VALUES...AND HAVE OPTED TO MENTION SOME STORMS MAY BE SEVERE A BIT WEST OF I-65 AND FURTHER EAST SUNDAY MORNING...BUT EXPECT SEVERE STORMS TO BE ISOLATED IN OCCURRENCE AT THIS TIME DUE TO THE QUESTIONS INVOLVING INSTABILITY. BETTER DELINEATION OF THIS AREA WILL COME WITH LATER SHIFTS AS TIMING AND STRENGTH OF THE SQUALL LINE BECOMES MORE CERTAIN. THE FLOW BECOMES UNIDIRECTIONAL IN THE WAKE OF THE CONVECTIVE LINE AND WEAKENS DRAMATICALLY. MODEL SOUNDINGS SHOW A MARKED IMPACT FROM SUBSIDENCE IN THE WAKE OF THE LINE. WILL HAVE CATEGORICAL POPS FOR MOST OF THE AREA SUNDAY MORNING THEN POPS TAPER OFF TO CHANCE OVER THE WESTERN FOURTH OF THE AREA SUNDAY AFTERNOON WITH LIKELY POPS FOR MUCH OF THE REMAINING PORTION. WHILE GUIDANCE IS IN AGREEMENT ON THE TRAILING FRONT MOVING THROUGH THE FORECAST AREA SUNDAY NIGHT...THE GFS HAS BEEN STRUGGLING WITH THE HANDLING OF AN UPPER LOW IN THE BASE OF THE TROF AND HAS A SECONDARY SURFACE LOW DEVELOPING OVER THE NORTH CENTRAL GULF AND ADVANCING INTO THE MARINE AREA SUNDAY NIGHT. THE ECMWF IN CONTRAST SLOWS THE SURFACE LOW WHILE MOVING TO NEAR THE CENTRAL ALABAMA/GEORGIA BORDER SUNDAY NIGHT. DESPITE THESE DIFFERENCES...THERE IS GOOD SUPPORT FOR PRECIPITATION AND HAVE GONE WITH LIKELY POPS FOR MOST OF THE AREA EXCEPT FOR CATEGORICAL POPS OVER THE NORTHWEST FLORIDA PORTION WHERE THE BEST QPF AMOUNTS ARE EXPECTED. THE GFS THEN MOVES THE SURFACE LOW ACROSS THE EASTERN PORTION OF THE FORECAST AREA ON MONDAY...AND WHILE THE ECMWF DIFFERS...IT AT LEAST HAS AN INVERTED SURFACE TROF DEVELOP OVER EASTERN ALABAMA. HAVE GONE WITH LIKELY POPS FOR THE EASTERN TWO THIRDS OF THE AREA FOR MONDAY WITH CHANCE POPS FOR THE REMAINDER. SLIGHT CHANCE POPS FOLLOW FOR MONDAY EVENING FOR THE EASTERN PORTION THEN DRY CONDITIONS FOLLOW FOR THE REMAINDER OF THE NIGHT. HIGHS ON SUNDAY WILL BE A FEW DEGREES ABOVE NORMAL WITH MILD TEMPERATURES FOR MUCH OF THE AREA SUNDAY NIGHT. NEAR SEASONABLE TEMPERATURES WILL BE OVER THE EASTERN MOST PORTION FOR MONDAY TRENDING TO NEAR 10 DEGREES BELOW NORMAL OVER THE WESTERNMOST PORTION. LOWS MONDAY NIGHT WILL BE ABOUT FIVE DEGREES BELOW NORMAL. /29 .LONG TERM (TUESDAY THROUGH FRIDAY)...SHORTWAVE RIDGING BUILDS INTO THE REGION ON TUESDAY IN THE WAKE OF THE UPPER TROF WHILE ANOTHER UPPER TROF ADVANCES ACROSS THE PLAINS. THIS NEXT SYSTEM ADVANCES ACROSS THE EASTERN STATES THROUGH THURSDAY WITH SUBTLE RIDGING BUILDING INTO THE REGION ON FRIDAY. A SURFACE RIDGE BUILDS ACROSS THE FORECAST AREA IN THE WAKE OF THE SURFACE LOW ON TUESDAY. A SURFACE LOW ASSOCIATED WITH THE ADVANCING UPPER TROF BRINGS A TRAILING COLD FRONT ACROSS THE LOWER MISSISSIPPI RIVER VALLEY TUESDAY NIGHT WHICH MOVES THROUGH THE FORECAST AREA BETWEEN WEDNESDAY AND THURSDAY MORNING...WITH CONTINUED UNCERTAINTY REGARDING THE TIMING OF THE FRONT. A SURFACE HIGH FOLLOWS IN THE WAKE OF THE FRONT AND ALLOWS FOR A RETURN FLOW TO BECOME ESTABLISHED ON FRIDAY AS ANOTHER SYSTEM ADVANCES ACROSS THE PLAINS. HAVE CONTINUED WITH A DRY FORECAST THROUGH THE PERIOD AS DESPITE THE FRONTAL BOUNDARY MOVING INTO THE AREA...DEEP LAYER MOISTURE REMAINS LIMITED. HIGHS ON TUESDAY WILL BE SLIGHTLY BELOW NORMAL THEN TREND TO A FEW DEGREES ABOVE NORMAL FOR THE REMAINDER OF THE PERIOD...WITH NEAR SEASONABLE OVERNIGHT LOWS. /29 && .AVIATION (12Z ISSUANCE)...MVFR TO IFR CONDITIONS THROUGH ABOUT 15.14Z FOLLOWED BY MVFR TO VFR CONDITIONS THROUGH 16.00Z THEN MVFR TO IFR CONDITIONS THROUGH 16.12Z. EXPECT SOME LOW STATUS AND PATCHY FOG EARLY TODAY FOLLOWED BY INCREASING LOW TO MID CLOUDS TODAY AND TONIGHT WITH THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS APPROACHING FROM THE WEST AND NORTHWEST BETWEEN 16.09Z AND 16.12Z CONTINUING THROUGHOUT THE DAY ON SUNDAY AND POSSIBLY SUNDAY NIGHT. DAMAGING WINDS...TORNADOES...PERIODS OF HEAVY RAIN AND FREQUENT LIGHTNING WILL ACCOMPANY THE STRONGER THUNDERSTORMS MOSTLY SUNDAY MORNING. 32/EE && .MARINE...SOUTHERLY WINDS AND SEAS WILL BUILD TODAY AND TONIGHT AHEAD OF A VIGOROUS UPPER LEVEL DISTURBANCE MOVING EAST OUT OF TEXAS COMBINED WITH A DEVELOPING SURFACE LOW SHIFTING FROM THE LOWER GULF TO THE CENTRAL GULF COAST REGION SUNDAY AND SUNDAY NIGHT. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS CAN BE EXPECTED WITH THIS PATTERN DEVELOPING EARLY SUNDAY MORNING SHIFTING EASTWARD OVER THE MARINE AREA DURING THE DAY ON SUNDAY THEN BECOMING ENHANCED LATE SUNDAY AND SUNDAY NIGHT AS THE WEAK SFC LOWS TRACKS NORTHWARDS TOWARDS THE CENTRAL GULF COAST. DAMAGING WINDS...ISOLATED TORNADOES...HEAVY RAIN AND FREQUENT LIGHTNING WILL LIKELY ACCOMPANY THE STRONGER THUNDERSTORMS SUNDAY AND SUNDAY NIGHT. SOUTHERLY WINDS WILL BUILD TO NEAR 20 KNOTS OVER THE OPEN GULF WATERS LATE TONIGHT AND EARLY SUNDAY SHIFTING SOUTHWEST LATER IN THE DAY THEN NORTHWEST TO NORTHEAST OVERNIGHT AS SFC LOW APPROACHES FROM THE SOUTH. AS THE SFC LOW BEGINS TO MOVE OUT OF THE REGION DURING THE DAY ON MON A MODERATE TO STRONG WEST TO NORTHWEST WILL DEVELOP OVER THE MARINE AREA MONDAY NIGHT THROUGH TUESDAY MORNING WITH WINDS UP TO 20 TO 25 KNOTS MOSTLY MONDAY NIGHT AND EARLY TUESDAY MORNING. WITH THIS PATTERN WILL GO AHEAD AN ISSUE A SMALL CRAFT ADVISORY FOR THE OVERNIGHT AND DAYLIGHT HOURS ON SUN MAINLY FOR THE OPEN GULF WATERS FROM 0 TO 60 NM FROM SHORE. SMALL CRAFT ADVISORIES MAY BE NEEDED ALSO LATE MONDAY AND MONDAY NIGHT WITH THE WEST TO NORTHWEST FLOW. 32/EE && .PRELIMINARY POINT TEMPS/POPS... MOBILE 68 59 76 55 66 / 30 90 100 70 60 PENSACOLA 67 61 72 58 68 / 20 70 100 80 70 DESTIN 66 61 70 61 68 / 20 70 100 90 70 EVERGREEN 70 58 76 56 67 / 20 90 100 70 60 WAYNESBORO 70 58 76 49 59 / 30 100 80 60 50 CAMDEN 70 57 74 54 64 / 30 100 100 70 50 CRESTVIEW 70 59 74 56 71 / 20 70 100 80 70 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...NONE. FL...NONE. MS...NONE. GM...SMALL CRAFT ADVISORY FROM 1 AM SUNDAY TO 10 AM SUNDAY FOR THE FOLLOWING ZONES: COASTAL WATERS FROM DESTIN TO PENSACOLA FL OUT 20 NM...COASTAL WATERS FROM PENSACOLA FL TO PASCAGOULA MS OUT 20 NM...WATERS FROM DESTIN TO PENSACOLA FL FROM 20 TO 60 NM...WATERS FROM PENSACOLA FL TO PASCAGOULA MS FROM 20 TO 60 NM... &&
Posted on: Sat, 15 Mar 2014 10:51:22 +0000
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