Special Weather Statement, NWS Mobile, AL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
503 AM CDT MON MAY 25 2015

.SHORT TERM [MEMORIAL DAY THROUGH TUESDAY NIGHT]...SURFACE RIDGING
FROM THE MID ATLANTIC WILL EXTEND INTO THE NORTH CENTRAL GULF
AND CONTINUES TO EFFECT A STRONG ONSHORE FLOW THROUGH THE PERIOD.
FROM THE GFS360 LONGWAVE PROGS WE SEE THE WAVENUMBER 5 PATTERN
INDICATES A 500 MB TROUGH ORIENTED ALONG 60W AND FILLING AS AN
ANTICYCLONE EXTENDS OVER THE EASTERN PACIFIC AND ANOTHER EXTENDS
ALONG MOST OF THE ATLANTIC FROM THE ANTILLES TO THE AFRICAN COAST
ALONG 20N. THE GFS360 FULL SPECTRUM OF THE 500 MB PROG INDICATES A
500 MB ANTICYCLONE REMAINS ALIGNED OVER ONSLOW BAY CAUSING THE
GEOPOTENTIAL HEIGHTS AT 500 MB TO BE ORIENTED SUCH THAT WE WOULD
MAINTAIN A SOUTHWEST FLOW ALOFT THROUGH 12Z TUESDAY.

IN SHORT AS TO WHAT WILL HAPPEN FOR THE FIRST TWO PERIODS...SHOWERS
AND THUNDERSTORMS WILL BE MOVING IN. OUR POP FORECAST IN ITS
ENTIRETY FOR THE FIRST 24 HOURS IS PREDICATED ON QPF INDICATED BY
HIGH RESOLUTION NON HYDROSTATIC MODEL OUTPUTS AVAILABLE TO US.
WETBULB ZEROS WILL BE 12000 TO 13000 FEET INDICATING LARGE HAIL IS
UNLIKELY. WIND AT 925 MB IS INDICATED SOUTH AROUND 25 KNOTS SO
LIMITED ORGANIZATION OF CONVECTIVE CELLS CANNOT BE RULED OUT
ESPECIALLY CONSIDERING THAT WE FOUND A COUPLET ON ONE CELL EARLY
THIS MORNING SHORTLY AFTER 07Z IN WAYNE COUNTY BEFORE FORECAST TIME.
BUOYANCY IS MODERATE AND LOWER-LEVEL WIND SHEAR BASED ON RADAR DATA
WOULD SEEM TO REINFORCE THE RISK OF TRANSIENT SUPERCELLS BUT THE
VERTICAL WIND DISTRIBUTION AS FORECAST BY MODEL OUTPUTS INDICATES
SHEAR WOULD DIMINISH OVER THE SHORT TERM. SO WE BELIEVE THE OVERALL
SEVERE WEATHER RISK WILL REMAIN LIMITED.

SURFACE DEWPOINTS WILL BE REMAINING STEADY IN THE LOW 70S THE NEXT
24 HOURS AND PRECIPITABLE WATER WILL RISE TO SLIGHTLY ABOVE 2
INCHES. SURFACE BASED (SB) CAPE FORECAST CALCULATIONS INDICATE IT
WILL RANGE FROM 2000 J/KG TO THE MID 2000'S INLAND. AS THEY DID
YESTERDAY...FORECAST SOUNDINGS SHOW MIXED LAYER CAPE WILL BE ABOUT
HALF THE SB CAPE. LIFTED INDEX IS FORECAST -3 TO -4. ALL OF THESE
PARAMETERS TELL US CONVECTION COVERAGE AND RAIN PRODUCTION WILL
INCREASE THROUGH TODAY. FORECAST SOUNDINGS ARE MOIST ADIABATIC FOR
TEMPERATURE. DEWPOINT DEPRESSION IS ONLY A COUPLE OF DEGREES CELSIUS
TO 300 MB BEING INDICATIVE OF HEAVY RAINFALL RISK TODAY AND TONIGHT.

HIGHS TODAY IN THE LOW TO MID 80S. LOWS INLAND AROUND 70 GIVE OR
TAKE A DEGREE...AND MID 70S FURTHER TOWARD THE COAST.

THIS AFTERNOON'S WET MICROBURST RISK IS LOW. /77

FORECASTS CALL FOR UPPER LEVEL STORM SYSTEM/TROF TO PIVOT SLOWLY
EASTWARD OUT OF THE PLAINS TUESDAY...WITH AXIS OF THE TROF LINING UP
ACROSS THE MISSISSIPPI VALLEY TUESDAY NIGHT. WITH DEEP LAYER MOISTURE
REMAINING UNCHANGED (PRECIPITABLE WATER VALUES FROM 1.7 TO 1.9
INCHES) AN UNSETTLED WEATHER PERIOD CONTINUES INTO THE DAY TUESDAY AS
A SERIES OF MID LEVEL IMPULSES EMBEDDED IN THE HIGH LEVEL SOUTHWEST
FLOW EJECT NORTHEAST FROM THE WESTERN GULF...UP ACROSS THE
MISSISSIPPI AND TENNESSEE RIVER VALLEY. THESE FEATURES WILL AID IN
ASCENT ALONG WITH ANY PROPAGATING RAIN COOLED MESOSCALE BOUNDARIES
SET DOWN BY CONVECTION. DAYTIME INSTABILITY WILL BE IN PLACE WITH
MOST UNSTABLE POTENTIAL ENERGY LIFTING TO BETWEEN 2000 TO 2500 J/KG.
IF THERE ARE BREAKS IN THE CLOUD COVER...SOLAR INSOLATION WILL
LIKELY YIELD HIGHER INSTABILITY. THE DEGREE OF INSTABILITY IS MORE
THAN SUFFICIENT FOR STORM UPDRAFTS. WHAT IS LACKING OVER OUR LOCAL
AREA IS A STRONG LOW LEVEL WIND FIELD. STRONGEST MID LEVEL
ENERGY/ASCENT AND BETTER POTENTIAL FOR ORGANIZED STORMS LOOKS TO BE
TO OUR NORTH...LIFTING NORTHEAST UP ACROSS THE TENNESSEE RIVER VALLEY
TUESDAY...THEN UP ACROSS THE OHIO RIVER VALLEY/NORTHEASTERN US
TUESDAY NIGHT. GIVEN THE AMOUNT OF INSTABILITY THOUGH...CANNOT RULE
OUT A FEW SEVERE STORMS PRODUCING DAMAGING WINDS IN EXCESS OF 60 MPH.
OTHER HAZARDS IN AND NEAR STORMS WILL BE FREQUENT LIGHTNING ACTIVITY
AND LOCALLY HEAVY RAINS. WITH CLOUDS AND RAIN...WILL KEEP HIGHS ONLY
IN THE MID 80S. TEMPERATURES MAY VERY WELL NOT GET OUT OF THE
70S...IF ONSET OF RAINS BEGIN EARLY IN THE DAY AND PERSIST. OVERNIGHT
LOWS NEAR 70 INTERIOR TO LOWER/MID 70S COAST. /10

.LONG TERM [WEDNESDAY THROUGH SUNDAY]...THE FORECAST AREA REMAINS
POSITIONED UNDER A HIGH LEVEL SHEAR ZONE AT THE BASE OF A LOWER
AMPLITUDE UPPER TROF POSITIONED OVER THE EASTERN US WEDNESDAY AND
THURSDAY. DEEP MOISTURE REMAINS IN PLACE AND THERE IS A PRECIPITATION
SIGNAL IN THE LATEST 25.00Z OPERATIONAL GFS AND ECMWF OUTPUT TO
SUPPORT A LIKELIHOOD OF SHOWERS/STORMS EARLY IN THE MEDIUM RANGE. THE
STRONGER STORMS CAN BE EFFICIENT IN PRODUCING LOCALLY HEAVY
RAINS...BRIEF STRONG WIND GUSTS AND FREQUENT LIGHTNING ACTIVITY.

AT THE CLOSE OF THE MEDIUM RANGE...LOOK TO BE GETTING BACK INTO A
MORE SEASONAL DIURNAL CONVECTIVE MODE. ISOLATED/SCATTERED SHOWERS/STORMS
FORMING ON COASTAL SEABREEZE BOUNDARY DURING THE DAYTIME HOURS FRIDAY
THROUGH SUNDAY.

DAYTIME HIGHS IN THE MID/UPPER 80S. BEACH TEMPERATURES LOOK TO HOLD
INTO THE MID 80S...WITH FLOW OFF THE GULF. OF COURSE...TIMING OF
ONSET AND PERSISTENCE OF DAYTIME RAINS WILL HAVE A LARGE IMPACT ON
HOW HIGH TEMPERATURES GO DURING THE OUTLOOK. OVERNIGHT LOWS NEAR 70
INTERIOR TO MID 70S BEACH AREAS. /10

&&

.AVIATION...
25.12Z ISSUANCE...MODERATE SOUTH WIND OF 11 TO 15 KNOTS
WITH OCCASIONAL HIGHER GUSTS TO NEAR 25 KNOTS LIKELY FOR THE NEXT 24
HOURS. PERSISTENT SCATTERED TO BROKEN LOW CLOUDS IN THE IFR CATEGORY
OF 1500 TO 2500 FEET ESPECIALLY NEAR NUMEROUS CONVECTIVE CELLS
COMMENCING AROUND MID MORNING AND LASTING THROUGH MID-AFTERNOON.
VISIBILITY 3 TO 5 MILES IN RAIN WITH OCCASIONAL RESTRICTIONS TO
BELOW A MILE. /77

&&

.MARINE...MODERATE TO STRONG ONSHORE WINDS WILL CONTINUE INTO MID
WEEK. A SURFACE RIDGE WILL EXTEND FROM THE MID ATLANTIC WESTWARD
OVER THE SOUTHEASTERN UNITED STATES. WIND WILL DIMINISH SOMEWHAT
COMMENCING MIDWEEK DUE TO A FLATTENING PRESSURE GRADIENT BROUGHT
ABOUT BY THE RETREATING SURFACE RIDGE. HOWEVER WINDS ARE EXPECTED TO
REMAIN GENERALLY ONSHORE INTO THE WEEKEND. SHOWERS AND THUNDERSTORMS
WILL BECOME NUMEROUS TODAY AND DIMINISH THROUGH MIDWEEK. BAYS AND
AREA WATERWAYS WILL BE CHOPPY. SWAN CALCULATIONS OF SEA HEIGHTS
AGREED CLOSELY WITH THE WNA AND GWW WAVE MODELS...AS WELL AS WITH
THE BRETSCHNEIDER NOMOGRAM. /77

&&

.PRELIMINARY POINT TEMPS/POPS...
MOBILE      81  72  84  70  85 /  60  40  60  40  60
PENSACOLA   82  75  86  73  84 /  40  40  60  30  50
DESTIN      82  76  85  75  84 /  50  30  60  30  40
EVERGREEN   85  70  86  70  86 /  70  40  70  40  70
WAYNESBORO  81  69  84  69  85 /  60  40  70  60  60
CAMDEN      84  69  86  69  84 /  70  50  70  60  70
CRESTVIEW   85  71  86  70  88 /  50  30  60  30  60

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...HIGH RIP CURRENT RISK THROUGH TUESDAY AFTERNOON FOR LOWER
     BALDWIN-LOWER MOBILE.

FL...HIGH RIP CURRENT RISK THROUGH TUESDAY AFTERNOON FOR COASTAL
     ESCAMBIA-COASTAL OKALOOSA-COASTAL SANTA ROSA.

MS...NONE.
GM...NONE.
&&

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MOBILE AL
524 AM CDT MON MAY 25 2015

ALZ052-061-251130-
UPPER MOBILE AL-WASHINGTON AL-
524 AM CDT MON MAY 25 2015

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN WASHINGTON COUNTY
UNTIL 630 AM CDT...

AT 523 AM CDT...A STRONG THUNDERSTORM WAS LOCATED OVER DEER PARK...OR
8 MILES NORTHWEST OF CITRONELLE...MOVING NORTHEAST AT 25 MPH.

LOCATIONS IMPACTED INCLUDE...
SAINT STEPHENS...      DEER PARK...           WAGARVILLE...
VINEGAR BEND...        TIBBIE...              CORTELYOU...
BASSETTS CREEK...      REID SETTLEMENT...     HAWTHORN...
PRESTWICK...           WAGAR...               SEABOARD...

THE PRIMARY THREATS FROM THIS STORM ARE WIND GUSTS UP TO 55 MPH.
WINDS THIS STRONG COULD BLOW OFF TREE LIMBS AND ALSO BLOW AROUND
SMALL UNSECURED OBJECTS. SEEK SHELTER UNTIL THIS STORM HAS PASSED.

THIS STORM MAY CONTINUE TO INTENSIFY AND A WARNING MAY SOON BE
NEEDED. PLEASE CONTINUE TO MONITOR LOCAL RADIO OR TV FOR FURTHER
NATIONAL WEATHER SERVICE UPDATES OR POSSIBLE WARNINGS.

HAZARDOUS DRIVING CONDITIONS ARE EXPECTED. HEAVY RAINFALL WILL
GREATLY RESTRICT VISIBILITY AND CREATE PONDING OF WATER ON
ROADWAYS...WHICH MAY CAUSE VEHICLES TO HYDROPLANE. TRAVELERS ARE
URGED TO USE CAUTION.

TO REPORT SEVERE WEATHER...CALL (800) 284-9059.

LAT...LON 3140 8791 3139 8793 3137 8794 3106 8830
      3116 8844 3120 8844 3160 8808
TIME...MOT...LOC 1023Z 222DEG 22KT 3118 8833