Flash Flooding in Texas, November 17, 2003

SOUTH TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
1000 AM CST MON NOV 17 2003

.UPDATE...A TORNDADO WATCH IS IN EFFECT FOR VICTORIA AND CALHOUN
COUNTIES UNTIL 1 PM CST. ALTHOUGH HELICITY VALUES ARE BEST AROUND
HOUS AREA AND DECREASE FARTHER S...VCT AND CAL COUNTIES DO HAVE
SOME POTENTIAL FOR ROTATION. FEEL CWA WILL SEE A LULL ONCE THE S/WV
EXITS TO THE NE BY AROUND 18Z. ANOTHER EMBEDDED WEAK S/WV IS EVIDENT
ON SATELLITE TO THE WEST AND SW OF CW OVR MEX. MESO ETA TAKES THIS
S/WV MORE N THRU 18Z. THE MAIN TROF AXIS WL CONT TO SHFT E CLOSER TO
CWA THRU THE AFTERNOON. WITH DESTABILIZATION/DIURNAL HEATING...AND
ANOTHER S/WV...EXPECT REDEVELOPMENT BY LATE AFTERNOON/EVENING...WITH
A THREAT FOR SVR ONCE AGAIN...AS MODELS INDICATING SQUALL LINE JUST
AHD AND ALONG THE WSHFT/CF WHICH IS SCHEDULED SOMETIME BETWEEN 03Z
AND 06Z. FCST LOOKS OKAY AT THE MOMENT...BUT MAY BE ABLE TO DROP TOR
WATCH PRIOR TO 1 PM WITH THE POSSIBILITY OF ANOTHER ONE LATER.

TE...81

&&

.PREVIOUS DISCUSSION...
.SHORT TERM (TODAY THROUGH TUESDAY)...SHRAS/TSRAS CONTINUE TO
INCREASE IN COVERAGE THIS MORNING ACROSS THE RIO GRANDE PLAINS AND
NRN COASTAL BEND AS THE NOSE OF A STRONG JET STREAK OF 130+ KT
IMPINGES UPON THE AREA.  A FAVORABLE UPR DIV/DIFL PATTERN WL REMAIN
ACROSS MOST OF SOUTH TX THROUGHOUT THE DAY AND EVE AS A POTENT S/WV
APPROACHES FROM NRN MEXICO.  IT APPEARS THAT THE NRN ZONES WL BE
UNDER THE GUN THE MOST WITH THIS SYSTEM.  A STRONG S/SW LLJ WL TEND
TO LIMIT PCPN POTENTIAL FURTHER SOUTH.  WHILE THE OVERALL
INSTABILITY WL NOT BE TOO IMPRESSIVE GIVEN THE ABUNDANT
CLOUDS...THINK THE DYNAMICS WL BE ENOUGH TO GENERATE SOME STRONG TO
SVR STORMS.  EXPECT THE BEST BET TO ONCE AGAIN BE ACROSS THE NRN
HALF OF THE AREA WITH THE MAIN SVR THREAT BEING DAMAGING WINDS GIVEN
THE INCREASINGLY UNIDIRECTIONAL SHEAR PROFILE AND HIGH WBZ VALUES.
CONVECTION WL TEND TO BECOME MORE LINEAR WITH TIME AS A RESULT AND A
POSSIBLE SQUALL LINE BY THE AFTN/EVE IS REASONABLE TO ACCEPT.  THIS
LINE OF STORMS WL PUSH ACROSS MOST OF THE LAND AREAS BY MIDNIGHT
BEFORE SWEEPING THROUGH THE WATERS IN THE EARLY MORNING HOURS ON
TUE.  RAPID CLEARING IS EXPECTED TO BEGIN LATER TNT ACROSS THE WEST
AND THE REMAINDER OF THE AREA ON TUE AS A SECONDARY S/WV PUSHES EWD
AND THE PACIFIC FNT CLEARS THE AREA.  A SURGE IN WIND IS EXPECTED ON
TUE WITH THIS SECOND WAVE AND WL PRODUCE BREEZY/WINDY CONDITIONS.
WL GO A LTL BIT WARMER WITH TEMPS ON TUE GIVEN THE EXCELLENT MIXING
AND PACIFIC NATURE OF THE FNT.

WITH THE INCREASING JET DYNAMICS AND EXPECTED LLJ INCREASE TO 30-40
KTS...WL GO WITH SCA CONDITIONS TDA/TNT FOR THE WATERS.  WINDS WL
ACTUALLY SLACKEN OFF A BIT TNT BEFORE INCREASING ONCE AGAIN ON TUE
BEHIND THE FNT.

&&

.LONG-TERM (TUESDAY NIGHT THROUGH SUNDAY)...MAIN FORECAST PROBLEMS
IN THE LONG TERM WILL BE TEMPERATURES AND POTENTIAL FOR LINGERING
SCA CONDITIONS TUESDAY NIGHT INTO WEDNESDAY.  GFS AND ETA CONTINUE
TO SLOWLY BUILD HIGH PRESSURE OVER SOUTH TEXAS THROUGH THE MIDDLE OF
THE WEEK.  GRADIENT IS PROGGED TO REMAIN TIGHT OVER THE WESTERN GULF
THROUGH WEDNESDAY SO WILL LIKELY NEED TO KEEP SCA CONDITIONS UNTIL
THEN. COLD ADVECTION WILL BEGIN SUBSIDE TUESDAY NIGHT BUT
TEMPERATURES WILL LIKELY FALL WELL INTO THE 40S ESPECIALLY OVER
NORTHERN AREAS.  TEMPERATURES WILL MODERATE LATER THIS WEEK AS
RETURN FLOW DEVELOPS.  LATEST CANADIAN AND GFS SHOW UPPER TROUGH
PROGRESSING THROUGH THE WESTERN STATES NEXT WEEKEND.  THERE ARE SOME
DISCREPENCIES WITH SURFACE FEATURES BUT APPEARS THAT FRONT WILL
APPROACH THE REGION BY SUNDAY. THINK SUFFICIENT MOISTURE WILL BE
AVAILABLE FOR SOME CONVECTION SO FOR NOW...WILL KEEP SLIGHT CHANCE
FOR SHOWERS GOING FOR SUNDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
CORPUS CHRISTI 85 64 81 49 / 20 70 10 00
VICTORIA       82 61 77 46 / 50 80 10 00
LAREDO         83 60 80 50 / 40 40 00 00

&&

.CRP...WATCHES/WARNINGS/ADVISORIES...SCA FOR ALL WATERS.

&&

80/MB...SHORT TERM
72/AP...LONG-TERM

GMZ230-235-250-255-270-275-TXZ229>234-239>247-181200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
840 AM CST MON NOV 17 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH TEXAS.

.DAY ONE...TODAY AND TONIGHT

A TORNADO WATCH IS IN EFFECT UNTIL 100 PM CST FOR VICTORIA AND
CALHOUN COUNTIES. THERE IS A SLIGHT RISK OF SEVERE WEATHER TO THE
NORTH OF AN ENCINAL TO SKIDMORE TO ROCKPORT LINE THIS AFTERNOON AND
EVENING. THE MAIN THREAT WILL BE FROM DAMAGING WIND GUSTS.  THIS IS
DUE TO AN APPROACHING STRONG UPPER LEVEL DISTURBANCE AND STRONG JET
STREAM. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE THROUGH EARLY AFTERNOON ACROSS MAINLY AN AREA STRETCHING
FROM LASALLE COUNTY EASTWARD TO ARANSAS COUNTY.  HOWEVER A MORE
ORGANIZED BAND OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
IN ADVANCE OF A COLD FRONT LATER THIS AFTERNOON ACROSS THE RIO GRANDE
PLAINS AND NORTHERN COASTAL BEND.  THIS BAND OF SHOWERS AND
THUNDERSTORMS WILL THEN PUSH EASTWARD THIS EVENING ACROSS THE
REMAINDER OF SOUTH TEXAS.  STRONG WIND GUSTS BETWEEN 40 AND 60 MPH
WILL BE POSSIBLE ACROSS THE SLIGHT RISK AREA.  OTHERWISE...HEAVY
RAINFALL WILL ACCOMPANY SOME OF THESE SHOWERS AND THUNDERSTORMS TODAY
AND THIS EVENING.  RAINFALL AMOUNTS UP TO TWO INCHES WILL BE POSSIBLE
BETWEEN COTULLA AND VICTORIA THROUGH THIS EVENING.  IMPROVING
CONDITIONS ARE EXPECTED BY MIDNIGHT ACROSS THE RIO GRANDE PLAINS AND
AFTER MIDNIGHT ELSEWHERE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE COLD FRONT WILL MOVE OFFSHORE ON TUESDAY.  STRONG NORTHWEST
WINDS BEHIND THE FRONT WILL PRODUCE SMALL CRAFT ADVISORY CONDITIONS
OVER THE WATERS THROUGH THE MIDDLE OF THE WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED AGAIN THIS AFTERNOON AND EVENING.

TE

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
759 AM CST MON NOV 17 2003

TXZ234-247-171900-
CALHOUN-VICTORIA-
INCLUDING THE CITIES OF PORT LAVACA...PORT OCONNOR AND VICTORIA
759 AM CST MON NOV 17 2003

...A TORNADO WATCH IS IN EFFECT FOR CALHOUN AND VICTORIA COUNTIES...

THE NATIONAL WEATHER SERVICE HAS ISSUED A TORNADO WATCH VALID UNTIL
100 PM CST MONDAY AFTERNOON. THE WATCH INCLUDES THE COUNTIES OF
CALHOUN AND VICTORIA. SOME CITIES INCLUDED IN THE WATCH ARE PORT
LAVACA...PORT OCONNOR...SEADRIFT AND VICTORIA.

A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR TORNADOES TO OCCUR
IN OR NEAR THE WATCH AREA. IF TORNADOES DO IN FACT DEVELOP OR ARE
SPOTTED...THEN A TORNADO WARNING WILL BE ISSUED.

EMERGENCY MANAGERS AND SPOTTER GROUPS SHOULD BE PREPARED FOR POSSIBLE
ACTIVATION. RESIDENTS ACROSS SOUTH TEXAS SHOULD REMAIN ALERT AND BE
READY TO QUICKLY ACT IF THREATENING WEATHER APPROACHES YOUR AREA. IF
SEVERE WEATHER THREATENS YOUR AREA...THEN MOVE TO AN INTERIOR ROOM
AND LAY DOWN ON THE FLOOR. IF CAUGHT OUTSIDE...LAY FLAT DOWN ON THE
GROUND...PREFERABLY IN A DITCH OR OTHER LOW SPOT. NEVER TRY TO OUTRUN
SEVERE WEATHER.

MB