Severe Thunderstorm Warning 81, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
245 PM CST SAT DEC 01 2001

THICK CLOUD COVER REMAINS OVER DEEP SOUTH TEXAS THIS AFTERNOON...PER
LATEST VISIBLE SATELLITE LOOP.  IN ADDITION TO THE CLOUD COVER...
KBRO REFLECTIVITY DATA INDICATES THAT A NORTHWEST-SOUTHEAST ORIENTED
BAND OF SHOWERS AND A COUPLE OF THUNDERSTORMS CONTINUES TO PROPAGATE
SLOWLY NORTHWARD FROM NORTHERN MEXICO.  THE CLOUD COVER AND PRECIP
IS LIKELY A RESULT OF UVV GENERATED BY A SUBTLE MID-LEVEL SHORTWAVE
TROUGH...SEEN IN WV IMAGERY MOVING ACROSS THE VALLEY...AS WELL AS
LOW-LEVEL FORCING FROM A WEAK INVERTED SURFACE TROUGH OVER THE
REGION.  BANDED NATURE OF REFLECTIVITY ALSO SUGGESTS THAT ISENTROPIC
LIFT MAY BE CONTRIBUTING TO THE VERTICAL MOTION FIELD...AND THIS IS
SUPPORTED BY 01/12Z MESOETA MODEL GUIDANCE...WHICH SUGGESTS STRONG
LIFT AND PRESSURE ADVECTION OCCURRING ALONG THE 300K ISENTROPE.

CLOUD COVER AND DECENT CHANCES OF RAIN SHOULD PERSIST THROUGH SUNDAY
NIGHT/EARLY MONDAY...AS A COUPLE OF WEAK SHORTWAVE TROUGHS AND
ABUNDANT PACIFIC MOISTURE MOVE ACROSS THE AREA IN THE MID-LEVEL
SOUTHWESTERLY FLOW.  GUIDANCE INDICATES THAT ISENTROPIC LIFT WILL
DECREASE LATER TONIGHT...BUT MODEL QPF PRODUCTS INDICATE WIDESPREAD
COVERAGE OF RAIN TOMORROW.  OVERALL...WEAK LIFT WILL BE PRESENT OVER
THE AREA VIA WAVES IN THE SUBTROPICAL JET...AND THIS SHOULD ACT ON
AN INCREASINGLY MOIST TROPOSPHERE TO GENERATE RAIN AND A FEW
THUNDERSTORMS.

MEDIUM AND LONG RANGE GUIDANCE CONTINUES TO FORECAST MID/UPPER LEVEL
RIDGING BEGINNING TO BUILD OVER THE AREA ON MONDAY...AND PERSISTING
THROUGH LATE THURSDAY.  THE MRF HAS BEEN CONSISTENT IN MOVING AN
ELONGATED AXIS OF POSITIVE VORTICITY ACROSS THE SOUTHERN PLAINS LATE
THURSDAY...WHICH WILL BREAK DOWN THE RIDGING OVER DEEP SOUTH TEXAS.
THE SURFACE REFLECTION OF THIS FEATURE WILL BE A PACIFIC COLD
FRONT...PROGGED TO PASS THROUGH THE VALLEY LATE THURSDAY NIGHT.  A
BRIEF PERIOD OF MOSTLY CLOUDY SKIES AND A SLIGHT CHANCE OF PRECIP
WILL ACCOMPANY THE FRONTAL PASSAGE...WITH MOSTLY CLEAR CONDITIONS
EXPECTED FOR THE REMAINDER OF FRIDAY AND SATURDAY.

MARINE...CURRENT OBS FROM BUOY020 INDICATE AN EAST WIND AT 15-20
KNOTS AND SEAS BUILDING TO 6 FEET OFFSHORE THIS AFTERNOON.
HOWEVER...WILL NOT MAKE MAJOR ADJUSTMENTS TO CWF AS SCEC STATEMENT
SHOULD COVER THE SITUATION.  SCATTERED SHOWERS AND THUNDERSTORMS
WILL CONTINUE THROUGH MONDAY...AND SOUTHEAST FLOW SHOULD RETURN TO
THE AREA AS EARLY AS TOMORROW.

PRELIMINARY NUMBERS:
BRO EB 067/077 067/079 068 40/40/30/20/00
HRL EB 065/077 065/079 066 40/40/30/20/00
MFE EB 063/076 064/078 066 40/40/30/20/00
RGC EB 060/075 061/077 063 40/40/30/20/00
SPI EB 069/075 070/077 071 40/40/30/20/00

SYNOPTIC...DD (65) / MARINE-AVIATION-MESO...PY (69)

INTERNET ADDRESS...WWW.SRH.NOAA.GOV/BRO

.BRO...NONE.

TXZ248>257-020300-

DEEP SOUTH TEXAS HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BROWNSVILLE TX
100 PM CST SAT DEC 01 2001

...DEEP SOUTH TEXAS HAZARDOUS WEATHER OUTLOOK...

SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL PREVAIL ACROSS DEEP
SOUTH TEXAS THROUGH THE AFTERNOON AND EVENING HOURS.  DEEPER
MOISTURE WILL PERSIST ACROSS SECTIONS OF WESTERN HIDALGO COUNTY
WHERE RAINFALL TOTALS WILL AVERAGE NEAR ONE QUARTER INCH THROUGH THE
AFTERNOON.  STRONGER STORMS OVER NORTHERN MEXICO WILL MOVE NORTH AND
MAY AFFECT THE LOWER VALLEY BY LATE AFTERNOON.  ALTHOUGH SEVERE
WEATHER IS NOT EXPECTED...SOME OF THE THUNDERSTORMS COULD BECOME
STRONG...WITH BLINDING DOWNPOURS AND GUSTY WINDS.

YURA