Flash Flood Warning 15, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
240 PM CDT FRI AUG 31 2001

VISIBLE SATELLITE IMAGERY THIS AFTERNOON INDICATES LOW/MID LEVEL
CLOUD COVER REMAINING ACROSS THE EASTERN TWO-THIRDS OF THE
CWA...WITH CLEARING SKIES IN THE WESTERN VALLEY.  WATER VAPOR
IMAGERY HINTS AT A SUBTLE VORT MAX MOVING EAST ACROSS SOUTHERN
TEXAS...WITH SUBSIDENCE NOTED IN THE MID-LEVEL ANTICYCLONIC FLOW
REGIME OVER THE WESTERN VALLEY.  THIS VORT MAX IS LIKELY INDUCING
THE VERY WEAK SURFACE LOW OVER JIM HOGG AND BROOKS COUNTIES AT THIS
TIME.  WILL PRIMARILY USE THE 31/12Z AVN FOR THIS FORECAST...AS IT
SEEMS TO HAVE BETTER INITIALIZED THE MID-LEVEL AND SURFACE FEATURES
THAT ARE OF MOST IMPORTANCE TO DEEP SOUTH TEXAS.  AS THE VORT MAX
OVER SOUTH-CENTRAL TEXAS CONTINUES TO MOVE EAST...SUBSIDENCE
COMBINED WITH WEAK CONFLUENT FLOW AT 500 MB...AND LACK OF ANY WAVES
UPSTREAM SHOULD HELP TO KEEP THINGS RELATIVELY QUIET AROUND THE AREA
TONIGHT.  HOWEVER...GIVEN THE VERY MOIST AIRMASS OVER THE
AREA...WILL MAINTAIN ISOLATED POPS TONIGHT.  UPPER RIDGING TRIES TO
BUILD OVER THE AREA ON SATURDAY AND SUNDAY...BUT WITH ONLY VERY
SLIGHT FLUCTUATIONS IN 500 MB HEIGHT AND THE PRESENCE OF A WEAK 500
MB TROUGH OVER CENTRAL TEXAS...WILL MAINTAIN ISOLATED TO LOW-END
SCATTERED POPS THROUGH SUNDAY NIGHT.

BY LABOR DAY...MODELS ARE FORECASTING THE MID-LEVEL TROUGH TO
AMPLIFY OVER TEXAS...WITH A TRANSITION TO SHARP MID/UPPER LEVEL
NORTHWEST FLOW OVER THE AREA.  THIS WILL ONLY SERVE TO INCREASE THE
PRECIPITATION CHANCES ACROSS THE AREA...ONCE AGAIN...AS NUMEROUS
MID-LEVEL WAVES ARE ALLOWED TO MOVE SOUTHEAST AND ACROSS SOUTH TEXAS
IN THE DIFFLUENT FLOW PATTERN AT 500 MB.  WILL GO WITH CHANCE POPS
EACH DAY THROUGH THURSDAY...AS TROFFING REMAINS OVER THE AREA.

MARINE...SOUTHEAST WINDS AROUND 15 KNOTS PRODUCING 6 TO 7 FOOT SEAS
AT BUOY 020.  THUS...SCA WILL BE MAINTAINED FOR NOW.  MODERATE
SOUTHEAST WINDS WILL PREVAIL THROUGH NEXT WEEK.  SHOWERS AND
THUNDERSTORMS WILL REMAIN IN THE FORECAST...WITH THE BEST CHANCES AT
THE BEGINNING OF NEXT WEEK.

PRELIMINARY NUMBERS:
BRO BB 078/095 078/095 078  20/30/20/30/20
HRL BB 077/096 077/096 077  20/30/20/30/20
MFE BB 078/098 078/098 078  20/30/20/30/20
RGC BB 077/099 077/099 077  20/30/20/30/20
SPI BB 079/089 079/089 079  20/30/20/30/20

SYNOPTIC...DD (65) / AVIATION-MARINE...HG (52) / MESO...TA

.BRO...FFA FOR TXZ 248-249-250-251.
       SCA FOR GMZ 130-150-155-170-175.

TXZ248>255-010230-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BROWNSVILLE TX
730 PM CDT FRI AUG 31 2001

...THUNDERSTORMS PRODUCING DANGEROUS CLOUD TO GROUND LIGHTNING...
AND VERY HEAVY RAIN...WERE APPROACHING THE LOWER VALLEY...

AT 730 PM...AN AREA OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
PRODUCING LOCALLY HEAVY RAIN...GUSTY WINDS...AND DANGEROUS
CLOUD TO GROUND LIGHTNING....EXTENDED FROM JUST NORTH OF PORT
MANSFIELD TO SULLIVAN CITY AND CONTINUED WEST INTO MEXICO.  THESE STORMS
WERE MOVING SOUTHEAST AT 30 MPH.

RIO GRANDE CITY...EDINBURG...MCALLEN...PORT MANSFIELD...RAYMONDVILLE...
AND SURROUNDING COMMUNITIES WILL LIKELY EXPERIENCE THIS AREA OF
THUNDERSTORMS BETWEEN 745 AND 800 PM.

IF THESE STORMS HOLD TOGETHER...THEN THEY SHOULD AFFECT THE
HARLINGEN...BROWNSVILLE...PORT ISABEL...SOUTH PADRE ISLAND AND
SURROUNDING COMMUNITIES BETWEEN 830 AND 930 PM.

STAY TUNED TO NOAA WEATHER RADIO...AND YOUR FAVORITE RADIO OR TV
STATION FOR FURTHER UPDATES.