Severe Thunderstorm Warning 26, NWS Brownsville, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
834 PM CDT WED MAY 27 2009

.DISCUSSION...VERY RARE AND POTENT OUTFLOW FROM CONVECTION NORTH OF
OUR REGION FIRED OFF SVR TSTMS W/HAIL NEAR GOLF BALL SIZE OVER
KENEDY AND CAMERON COUNTIES. THIS OUTFLOW BOUNDARY WOULD NORMALLY
BRING A QUICK SHOT OF NORTHEAST WINDS TO NEAR 35 MPH...INSTEAD
NORTHEAST WINDS OF 35 TO 50 MPH PERSISTED FOR NEARLY 3 HOURS WITH
TSTMS DEVELOPING PRE AND POST BOUNDARY PASSAGE. THIS WAS THE LIFTING
MECHANISM THAT OUR VOLATILE ATM HAS BEEN WAITING FOR...AND MORE
NEEDED LIFT IS SCHEDULED FOR THURSDAY. SPC WRITES...MODERATE TO
STRONG INSTABILITY IS EXPECTED TO LINGER IN THE CONTINUING PRESENCE
OF STEEP MID-LEVEL LAPSE RATES ACROSS THE LOWER RIO GRANDE
VALLEY...WHERE MID-LEVEL INHIBITION APPEARS LIKELY TO REMAIN
RELATIVELY WEAK AS WELL.  THERE ARE INDICATIONS IN MODEL GUIDANCE
THAT FORCING ASSOCIATED WITH A WAVE WITHIN THE SUBTROPICAL STREAM
COULD CONTRIBUTE TO STORM DEVELOPMENT OFF THE HIGHER TERRAIN OF
MEXICO BY MIDDAY THURSDAY...BEFORE SPREADING ACROSS SOUTHERN TEXAS
COASTAL AREAS BY EARLY THURSDAY EVENING. LOW-LEVEL FLOW FIELDS ARE
PROGGED TO BE WEAK...BUT AN EASTERLY COMPONENT BENEATH MODEST
WESTERLY MID/UPPER FLOW MAY PROVIDE SUFFICIENT SHEAR FOR ISOLATED
SUPERCELLS. THIS ACTIVITY IS ALREADY SHOWING ITSELF ALONG THE LEE
SIDE OF THE SIERRA MADRE ORIENTALS...WITH TSTMS COOKING 60 MILES SE
OF STARR COUNTY AND 70 MILES NW OF EXTREME WESTERN ZAPATA COUNTY. BE
WEATHER AWARE TOMORROW
&&

.PREV DISCUSSION.../ISSUED 220 PM CDT WED MAY 27 2009/MAIN FOCUS IN
THE SHORT TERM WILL CONTINUE TO BE THREAT FOR STRONG TO SEVERE
THUNDERSTORMS ACROSS PORTIONS OF DEEP SOUTH TX. CONTINUE TO MONITOR
MCS THAT DEVELOPED DURING THE MRNG HRS NORTH OF THE AREA AND
CONTINUES TO IMPACT AREAS AROUND THE COASTAL BEND. THE ACTIVITY HAS
BEEN SHIFTING SEWD AND RADAR TRENDS HAVE INDICATED DEVELOPMENT ON
THE SOUTHERN FRINGES CLOSER TO OUR CWA. ANTICIPATE THIS TREND TO
CONTINUE WITH ADDITIONAL DEVELOPMENT TO THE SOUTH ACROSS PORTIONS OF
THE CENTRAL AND EASTERN BRO CWA THRU THE AFTN/EVE POSSIBLY ALONG
OUTFLOW. MAIN THREAT WITH THE MOST SEVERE ACTIVITY WILL BE LARGE
HAIL AND DAMAGING WINDS. HEAVY RAINFALL WILL ALSO BE A CONCERN. SPC
KEEPS DEEP SOUTH TX IN SLIGHT RISK FOR SEVERE WEATHER THRU 12Z FRI.
DECIDED TO RETAIN HIGHER POPS HERE THRU TNGT AND THEN BREAK THEM
SLIGHTLY OVRNGT AND THEM BUMP THEM BACK UP DURING THE DAYTIME THU.
SFC COLD FRONT WILL CONTINUE TO SAG SWD INTO OUR AREA THRU THU.
EMBEDDED S/WV ENERGY IN THE MID LEVEL FLOW IS EXPECTED TO CONTINUE
TO INTERACT WITH THE VERY MOIST AND UNSTABLE AIRMASS THRU THAT TIME
PERIOD. PATTERN LOOKS TO PREVAIL THRU FRI AND WILL CONTINUE TO
MENTION CHC FOR THUNDERSTORMS. SLIGHTLY DRIER CONDITIONS POSSIBLE
FOR THE UPCOMING WEEKEND AS ACTIVITY MAY SHIFT BACK TO THE WEST AND
SOUTHWEST ACROSS MEXICO AND POTENTIALLY HAVE ONLY AN IMPACT ALONG
THE RIO GRANDE RIVER AND ADJACENT COUNTIES. CONTINUED BLEND OF
MAV/MET TEMPS THRU THE SHORT TERM AS LATEST GUIDANCE CONTINUES TO
REMAIN IN FAIRLY GOOD AGREEMENT. OVERALL TEMPERATURE TREND SHOULD
CONTINUE TO EXHIBIT NORMAL TO SLIGHTLY ABOVE NORMAL FOR LATE MAY
THRU THE FCST PERIOD.
&&

.MARINE...SEAS WERE NEAR 6 FEET WITH EAST WINDS NEAR 17 KNOTS AT
BUOY020 THIS EVENING. SEAS SHOULD SUBSIDE TONIGHT AS THE OUTFLOW
BOUNDARY THAT GENERATED SEVERE THUNDERSTORMS ACROSS THE COASTAL
WATERS THIS AFTERNOON HAS MOVED TO THE SOUTH. LIGHT TO MODERATE EAST
TO SOUTHEAST WINDS SHOULD PREVAIL TONIGHT INTO THURSDAY WITH A
RELATIVELY WEAK PRESSURE GRADIENT ACROSS THE WESTERN GULF OF MEXICO.
WINDS AND SEAS WILL BRIEFLY INCREASE WITH SHOWERS AND THUNDERSTORMS
THAT MOVE THROUGH THE COASTAL WATERS THURSDAY.
&&

.AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE HIGH
CLOUDS FROM THE ANVIL TOPS FROM THUNDERSTORMS OVER NORTHEAST MEXICO
CONTINUE TO MOVE ACROSS DEEP SOUTH TX THIS EVENING. VFR CONDITIONS
SHOULD PREVAIL TONIGHT AND THURSDAY WITH THUNDERSTORMS PROVIDING
MVFR CONDITIONS LATE TONIGHT INTO EARLY THURSDAY.
&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  78  88  75  88 /  50  50  30  30
BROWNSVILLE          75  89  74  90 /  50  50  30  30
HARLINGEN            75  91  75  91 /  50  50  30  30
MCALLEN              76  90  75  91 /  50  50  30  30
RIO GRANDE CITY      78  94  75  93 /  50  50  30  30
SOUTH PADRE ISLAND   79  86  77  85 /  50  50  30  30

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WWW.WEATHER.GOV/BROWNSVILLE

58/61

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1228 AM CDT THU MAY 28 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1226 AM     TSTM WND GST     5 N SAN YGNACIO         27.11N 99.45W
05/28/2009  E40 MPH          XXX                XX   LAW ENFORCEMENT

            ZAPATA COUNTY SHERIFFS DEPARTMENT REPORTED WINDS OF 35 TO
            40 MPH 5 MILES NORTH OF SAN YGNACIO.

&&

TOMASELLI