Severe Thunderstorm Warning 12, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1215 PM CDT SUN APR 20 2003

CORRECTED FOR RGC PRELIMINARY NUMBERS

DISCUSSION...SHORT TERM PROBLEM IS THE COLD FRONT ADVANCING SLOWLY
SOUTH INTO DEEP SOUTH TEXAS. THE CURRENT ZONE PRODUCT CARRIES A 50
PERCENT CHANCE OF SHOWERS AND THUNDERSTORMS FOR THE FIRST PERIOD OF
THIS FORECAST...TONIGHT...WITH PRECIPITATION CHANCES DECREASING
AFTERWARD BUT PERSISTING THROUGH WEDNESDAY. DEEP SOUTH TEXAS IS
DEPICTED IN A GENERAL THUNDERSTORM OUTLOOK AREA FOR THE NEXT THREE
PERIODS. LOOKING AT THE SOUNDING...LOW LEVEL MOISTURE IS
AVAILABLE...BUT LIFT WOULD NEED TO BE ENOUGH TO BREAK A DEEP
INVERSION/ISOTHERMAL LAYER. ONCE ACHIEVED...AVAILABLE ENERGY COULD
SUPPORT LARGE THUNDERSTORMS WITH HAIL AND DOWNBURST WIND POTENTIAL.
SOME CONVECTION NOW FIRING TOWARD THE NORTHWEST CORNER OF THE DEEP
SOUTH TEXAS COUNTY WARNING AND FORECAST AREA IN THE VICINITY OF THE
FRONTAL BOUNDARY.

CAN NOT ARGUE MUCH WITH THE SHORT TERM ASSESSMENT. THE FRONTAL
BOUNDARY PUSH APPEARS TO REMAIN WEAK...WITH SLOW PROGRESS ACROSS
DEEP SOUTH TEXAS THE NEXT 24 TO 36 HOURS. SURFACE HIGH PRESSURE
SLIDES EAST MORE THAN SOUTH AND SOUTHERN STREAM DISTURBANCES WITH
SOME UPPER JET SUPPORT REMAIN ACTIVE OVER DEEP SOUTH TEXAS...
ALLOWING CLOUDY UNSETTLED WEATHER TO CONTINUE. MAY KEEP THE MENTION
OF ISOLATED SEVERE IN FIRST PERIOD...BUT NOT BEYOND AT THIS POINT.
RAINFALL COULD BE BRIEFLY HEAVY IN THE STRONGEST STORMS...AS
MOVEMENT IS ALSO MODERATE AND WOULD SUPPORT IT.

WINDS WILL BE GENERALLY WEAK THE NEXT THREE PERIODS...WITH NOT MUCH
CHANGE DUE TO THE FRONT...BUT SLIGHTLY STRONGER SOUTHEAST WINDS ARE
EXPECTED ON TUESDAY AS ANOTHER STORM SYSTEM DEVELOPS OUT WEST WITH
PRESSURE FALLS IN THE HIGH PLAINS. LOW PRESSURE TROUGHING EXTENDS TO
DEEP SOUTH TEXAS BY TUESDAY NIGHT WITH WINDS WEAKENING AGAIN.

THE COMBINATION OF GULF MOISTURE AND PERSISTENT CAPPING FLOW WILL
KEEP SKIES CLOUDY TO MOSTLY CLOUDY MUCH OF THIS WEEK...WITH A
PROGRESSIVE FLOW SENDING A SERIES OF SHORT WAVES INTO THE WEST. THIS
PATTERN DOES NOT ALLOW FOR A CLEARING SCENARIO RELATIVELY SOON.
TEMPERATURES WILL REMAIN NEAR NORMAL THROUGH THE FORECAST HOWEVER.

MARINE AND AVIATION TO BE POSTED WHEN AVAILABLE.

PRELIMINARY NUMBERS FOR COORDINATION PURPOSES ONLY...
BRO CC 068/080 068/082 069/082 50/40/20/20/20/10
HRL CC 065/081 066/083 068/084 50/40/20/20/20/10
MFE CC 067/082 067/084 069/086 50/40/20/20/20/10
RGC CC 065/083 065/085 067/087 50/40/20/20/20/10
SPI CC 068/079 068/080 069/080 50/40/20/20/20/10

.BRO...NONE.

60/54

THIS PRODUCT IS ALSO AVAILABLE ON OUR INTERNET WEB PAGE AT:
HTTP://WWW.SRH.NOAA.GOV/BRO

TXZ248>257-210900-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1215 PM CDT SUN APR 20 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR DEEP SOUTH TEXAS.

.DAY ONE...TODAY AND TONIGHT.

ISOLATED INTENSE THUNDERSTORMS WILL CONTINUE TO FORM ON THE MEXICAN
SIDE OF THE RIO GRANDE RIVER WEST OF LAREDO. SOME OF THUNDERSTORMS
MAY MOVE EAST ACROSS THE RIO GRANDE RIVER INTO ZAPATA...STARR...JIM
HOGG AND BROOKS COUNTIES. THESE STORMS MAY PRODUCE BRIEF
DOWNPOURS...FREQUENT DEADLY LIGHTNING...HAIL AND GUSTY WINDS. SOME
OF THESE STORMS MAY MOVE SOUTH AND EAST THROUGHOUT THE AFTERNOON
HOURS POSSIBLY AFFECTING HIDALGO...KENEDY...WILLACY AND CAMERON
COUNTIES LATER THIS AFTERNOON AND THIS EVENING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

SMALL CRAFT ADVISORIES ARE POSSIBLE WEDNESDAY AND THURSDAY...AS
DEEPENING SURFACE LOW PRESSURE IN WEST TEXAS PROMOTES STRONG
SOUTHEAST WINDS AND HIGH SEAS.

.SPOTTER INFORMATION STATEMENT.

SPOTTER ACTIVATION MAY BE NECESSARY LATER TODAY AND TONIGHT.

SPEECE