MOB issues Area Forecast Discussion (AFD) 405 FXUS64 KMOB 141105 AAA AFDMOB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOBILE AL 605 AM CDT MON JUL 14 2014 .UPDATE...FOR THE ANTICIPATED EVENT RAINFALL TUESDAY...WE REVIEWED THE MESOSCALE PICTURE INCLUDING MOISTURE TRANSPORT VALUES AS WELL AS SOME LATE ARRIVING EURO MODEL DATA...MODEL SOUNDINGS..06Z RUNS OF THE GFS...AND OTHER SOURCES...AND REVISED OUR RAINFALL ESTIMATE DOWN SOMEWHAT. OVER INLAND AREAS IT IS SLIGHT...TO ABOUT 1 TO 1.15 INCHES OVER MOST OF OUR AREA INLAND. THE BEACH AREAS AND ELSEWHERE WILL ALSO SHOW A DOWNWARD REVISION TO 1.15 TO 1.25 INCHES. 77/BD && .PREV DISCUSSION... /ISSUED 413 AM CDT MON JUL 14 2014/ SHORT TERM [TODAY AND TONIGHT]...WEATHER MAPS THIS MORNING SHOW A COMPLEX...LARGE UPPER LEVEL CYCLONIC GYRE OVER THE HUDSON BAY. THE SOUTHERN EXTENT OF THE ASSOCIATED HIGH LEVEL TROF EXTENDS FROM THE NORTHERN HIGH PLAINS...EAST ACROSS THE GREAT LAKES. AT THE BASE OF THE TROF AND FURTHEST TO THE SOUTH WAS A SURFACE FRONT DRAPED FROM THE TEXAS PANHANDLE TO ACROSS THE OHIO RIVER VALLEY. ALONG THE FRONTAL ZONE IS WHERE FORECASTERS SEE ORGANIZED CONVECTION/ENHANCED LIGHTNING ACTIVITY EARLY THIS MORNING. OVER THE CENTRAL GULF COAST...A BROAD MID LEVEL RIDGE WAS IN PLACE. SURFACE HIGH PRESSURE OVER THE WESTERN ATLANTIC CONTINUES TO NOSE SOUTHWEST TO WEST ACROSS THE CENTRAL GULF IN THE NEAR TERM. DEEP LAYER MOISTURE AROUND 2 INCHES ALONG WITH EMBEDDED IMPULSES IN THE HIGH LEVEL WEST/SOUTHWEST FLOW AND DAYTIME INSTABILITY FAVORS SCATTERED COVERAGE OF SHOWERS AND STORMS THROUGH THE COURSE OF THE DAY. THE FORECAST IS SUPPORTED AS FORECASTERS BEGINNING TO SEE DEVELOPMENT OFF THE LOUISIANA COAST TO THE MISSISSIPPI SOUND. MOVEMENT WAS NORTHEAST AT AROUND 15 MPH. THIS IS ALSO IN AGREEMENT WITH THE PRECIPITATION EVOLUTION IN THE HIGH RESOLUTION NCEP 4.0 KM WRF-NMM AND HRRR GUIDANCE. SOME OF THE ISOLATED STRONGER STORMS TODAY WILL LIKELY CONTAIN FREQUENT LIGHTNING ACTIVITY...BRIEF HEAVY RAINS AND BRIEF STRONG WIND GUSTS POSSIBLY FROM 40 TO 50 MPH. HIGH TEMPERATURES MOST AREAS TODAY FORECAST IN THE LOWER HALF OF THE 90S. OVERNIGHT LOWS AROUND 72 INTERIOR TO AROUND 78 COAST. /10 THIS AFTERNOONS WET MICROBURST RISK IS MODERATE. (MONDAY THROUGH TUESDAY)...A 5980 M UPPER HIGH CONTINUES TO DOMINATE THE SOUTHWESTERN STATES. A BINARY UPPER LOW MENTIONED ABOVE IS EVOLVING SO THAT BY MONDAY THE SOUTHERN CENTER IS FILLING SLIGHTLY WHILE IT MOVES SOUTHEAST ACROSS MINNESOTA AND THE GREAT LAKES. THE NORTHERN CENTER WILL BE LOCATED OVER WESTERN LABRADOR. THE SOUTHERN CENTER WILL MOVE OVER THE UPPER PENINSULA OF MICHIGAN AND RE-INTENSIFY SLIGHTLY. THAT WILL DIG A STRONG UPPER TROUGH INTO OUR REGION TUESDAY MORNING AND STRONG PERTURBATIONS WILL SWEEP SOUTH AROUND THE TROUGH. THIS WILL MOVE A COLD FRONT ACROSS OUR AREA TUESDAY INTO TUESDAY NIGHT BEFORE STALLING OFF THE NORTHERN GULF COAST WEDNESDAY. THIS SCENARIO IS PLAYING OUT A BIT MORE SLOWLY THAN IN PREVIOUS OUTPUTS AND IT IS COMPUTED TO EXTEND OVER OUR COASTAL REGION BY 00Z WEDNESDAY. FOR MONDAY...HAVE INCREASING CHANCES FOR RAIN. WITH THE UPPER SYSTEM HAVING LIMITED REACH THE CHANCE OF SEEING ANY LOW LEVEL WIND ABOVE 10 OR 15 KTS. THIS WILL LIMIT THE MOISTURE TRANSPORT AND THE 850 MB MOISTURE TRANSPORT VECTORS ARE POINTED NORTHEAST BUT WITH VERY SMALL MAGNITUDES. THERE IS SOME INSTABILITY OVER OUR AREA AHEAD OF THE FRONT...CAPE IS AROUND 2000 TO 2500 AND LI IS -4. PRETTY TYPICAL FOR A SUMMER DAY. EXTREMELY LOW HELICITY WILL MAKE A CHANCE OF WIDESPREAD ORGANIZED SEVERE WEATHER PRETTY CLOSE TO NIL. UPPER- LEVEL FORCING FOR ASCENT WILL LIKELY BE LIMITED AND MOST OF THAT REMAINS NORTHEAST OF OUR REGION INTO THE PIEDMONT REGION AND SOUTHEAST STATES. AN ISOLATED STORM APPROACHING OR MEETING SEVERE CRITERIA CANNOT BE RULED OUT...BUT AGAIN ORGANIZED SEVERE CONVECTION IS UNLIKELY WITH THIS FRONTAL PASSAGE. /77 LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)...GFS PROGNOSES STILL SHOW THE 500 MB TROUGH HAVING A SLIGHT POSITIVE TILT LOCATED OVER THE MISSISSIPPI AND OHIO VALLEYS WHILE THE PARENT LOW MOVES INTO SOUTHERN ONTARIO. IT BECOMES SLIGHTLY FLATTER AS IT STALLS WHILE ITS PARENT LOW MOVES FROM SOUTHERN ONTARIO MOVING INTO WESTERN LABRADOR. AT THAT TIME AT 500 MB...THE UPPER HIGH OVER THE SOUTHWEST STATES WILL HAVE ALMOST COMPLETELY COLLAPSED BY THURSDAY. THE OUTPUTS CONTINUE TO AGREE ON A COLD FRONT PUSHING PAST OUR AREA OFFSHORE BUT THE GFS DOES NOT PUSH IT AS STRONGLY AS THE EURO. SINCE THE EURO AND GFS HAVE MORE OR LESS SWITCHED SIDES ON TEMPERATURES THURSDAY MORNING OUR CONFIDENCE IS LEANING TOWARD THE GFS AND THE MEX OUTPUT. ALIGNMENT OF THE COLD FRONT WILL CONTINUE TO PHASE WITH THE WAVENUMBER 5 TROUGH TO OUR NORTH WHICH WILL BRING A NORTHWEST FLOW ALOFT OVER OUR REGION AROUND MIDWEEK. CONTINUE TO EXPECT MID LEVEL PERTURBATIONS IN THE 500 MB FLOW ALONG THE FRONT. TUESDAY NIGHT CAPES 2500 TO 3500 J/KG...LIFTED INDEX GENERALLY AROUND -4 DURING THAT PERIOD...AND PRECIPITABLE WATER CONSIDERABLY GREATER THAN 2 INCHES...WE EXPECT NUMEROUS SHOWERS AND THUNDERSTORMS TUESDAY AND CLEARING WEDNESDAY EXCEPT OVER THE GULF. IN THAT 48 HOUR PERIOD WE EXPECT INLAND AVERAGE RAINFALL OF AN INCH TO AN INCH AND A QUARTER WITH HIGHER TOTALS POSSIBLE WHERE CONVECTIVE TRAINS MAY SET UP. ALONG THE BEACH IT GETS CLOSER TO AN INCH AND A HALF TO 1.75 INCHES TEN TO 2,25 OVER THE GULF...AND GENERALLY THIS WILL BE HAPPENING AS THE FRONT STALLS AND CONTINUES RAINFALL OVER THE MARITIMES. CLEARING BEHIND THE FRONT WEDNESDAY...AND THURSDAY SHOULD BE CLOUD AND RAIN FREE BUT WHEN THE FRONT PULLS OFFSHORE THURSDAY EVENING WE EXPECT IT WILL START BACKING UP AND DISSIPATING...AND WITH THE RETURN OF ONSHORE FLOW THE ATMOSPHERE WILL RECOVER A MORE SEASONAL SUMMERTIME PROFILE WITH THE SEABREEZE AND ITS ATTENDANT EFFECTS. AS WE ALLUDED TO ABOVE...MEX AND EURO MODEL OUTPUTS HAVE SWITCHED SIDES ON POST-FRONTAL TEMPERATURE. WE ARE EXPECTING IT TO GET INTO THE MID 60S THURSDAY MORNING IN THE NORTHERN SECTIONS OF OUR AREA...UPPER 60S NORTH OF I-10...AND CLOSER TO 70 ALONG THE BEACH. SO AGAIN...THE GFS MOS CAME AROUND AS WE THOUGHT IT MIGHT...BUT SINCE ITS OUTPUTS CROSSED THOSE OF THE EURO...WE STAYED CLOSER TO MEX GUIDANCE THIS TIME. WILL KEEP WATCHING THESE MODEL CALCULATIONS IN FUTURE RUNS. /77 AVIATION [14.12Z KMOB/KBFM/KPNS TAF ISSUANCE]...EXPECT ISOLATED TO SCATTERED SHRA...POSSIBLE TSRA MOVING NORTHEAST IN OFF THE GULF TO BRING LOWER CIGS/VSBYS IN RA TO MVFR CATEGORIES THIS MORNING. BRIEF STRONG WIND GUSTS IN AND NEAR TSRA. MOST OF THE WEATHER LOOKS TO SHIFT NORTHEAST OF THE TERMINALS AFTER 18Z. AWAY FROM INFLUENCE OF TSRA...A LIGHT SOUTH/SOUTHWEST PREVAILING WIND FROM 8 TO 12 KNOTS EXPECTED THROUGH THE DAY. /10 MARINE...SURFACE HIGH PRESSURE NOSING WEST INTO THE CENTRAL GULF...BREAKS DOWN ON TUESDAY AS A FRONTAL BOUNDARY APPROACHES FROM THE NORTH. SOUTHWEST FLOW EARLY ON BECOMES MORE WESTERLY TUESDAY. THERE ARE INDICATIONS THAT THE FRONT COULD EASE DOWN INTO THE COASTAL WATERS EARLY WEDNESDAY MORNING...THEN BEGIN TO SLOW AND STALL OUT THROUGH THE DAY. FRONT DISSIPATES LATER IN THE WEEK AS A SYNOPTIC SCALE ONSHORE FLOW RETURNS. SEAS 1 TO 2 FEET THROUGH TUESDAY MAY BUILD ANOTHER FOOT OR SO TUESDAY NIGHT DUE TO INCREASE IN WESTERLY FETCH. WINDS...WAVES AND SEAS WILL BE LOCALLY HIGHER IN AND NEAR STORMS. FREQUENT LIGHTNING ACTIVITY ALSO A HAZARD IN MARINE STORMS. /10 && .PRELIMINARY POINT TEMPS/POPS... MOBILE 91 74 89 72 89 / 30 20 60 50 30 PENSACOLA 90 77 89 75 91 / 30 20 60 50 40 DESTIN 89 78 87 76 90 / 30 20 60 40 40 EVERGREEN 94 73 90 68 87 / 30 20 60 30 20 WAYNESBORO 93 72 90 65 88 / 30 20 50 40 20 CAMDEN 94 72 89 67 86 / 30 20 60 30 20 CRESTVIEW 92 73 90 72 93 / 30 20 60 40 40 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...NONE. FL...NONE. MS...NONE. GM...NONE. && $$
Posted on: Mon, 14 Jul 2014 11:05:59 +0000
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