Tornado Warning 31, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
851 PM CDT THU SEP 11 2003

THUNDERSTORMS PUSHING SOUTH AND NEARING THE NORTHWESTERN-MOST BORDER
OF THE CWA. OUTFLOW CONTINUES TO PUSH SOUTH AND AREA VWP INDICATE
GOOD FLOW IN LL NEARLY PERPENDICULAR TO THE BOUNDARY...FLOW
8-10KFT NEARLY PARALLEL. PW/IPWV RUNNING 1.7 TO 2.0 NEAR THE
BOUNDARY THOUGH OVER SETX THE AIRMASS GOT WORKED OVER PRETTY GOOD WITH
DEEP CONVECTION DURING THE AFTERNOON. LI OF -6 TO -8 STILL PRESENT
OVER THE SOUTHWEST ZONES AND HELICITY/SHEAR IN SW ZONES MAY POSE
ENOUGH OF PROBLEM THAT I WILL ADD MENTION OF SEVERE TO SW ZONES.
EXPECTING THAT THE CONVECTION SHOULD MOVE SOUTH SO WILL UPDATE ZONES
TO INCREASE POPS AND QPF AND NUDGE DOWN TEMPERATURES 2 TO 5 DEGREES.
UPDATE SHOULD BE OUT AROUND 915 PM.

45/37/31

.HGX...FLASH FLOOD WATCH.

PRELIMS...
CLL TE 068/085 069/088 065 +85
IAH TE 072/086 071/087 066 886
GLS TE 077/085 077/085 074 778

PREV DISC...
A DECENT SHORTWAVE TROUGH TO AFFECT SE TX OVER THE NEXT FEW PERIODS.
THE MAIN CHALLENGE WILL BE RAINFALL COVERAGE AND AMOUNTS...THOUGH
TEMPERATURES AND CLOUD COVER WILL BAT A CLOSE SECOND AND THIRD.  IN
CONSIDERING THE MODELS...THE GFS LOOKED MORE REALISTIC THAN THE ETA
IN BRINGING A PREFRONTAL TROUGH THROUGH SE TX FRIDAY AFTERNOON AND
EVENING...THEN THE ETA LOOKS MORE REALISTIC IN BRINGING THE ACTUAL
FRONT THROUGH LATE ON SATURDAY.  THE MESO-ETA LOOKED FAIRLY GOOD IN
ITS DEPICTION OF THE 500 MB HEIGHTS AND VORTICITY.  THUS...WILL TAKE
A COMPROMISE OF BOTH.

THE RAINFALL POTENTIAL LOOKS GOOD THROUGH TOMORROW EVENING.  ACCORDING
TO THE GFS...PW/S WILL GET OVER 2.1 INCHES DURING THIS PERIOD...NEAR 2
STANDARD DEVIATIONS ABOVE THE HISTORICAL NORM FOR THE LCH SOUNDING
SITE AND CLOSE TO IT FOR THE CRP SITE.  IN CONJUNCTION WITH THIS...THE
LOCAL FLASH FLOOD GUIDANCE WORKSHEET SUGGESTS RAINFALL POTENTIAL OF 1
TO 3 INCHES AND ISOLATED AMOUNTS OF 3 TO 6 INCHES POSSIBLE.  SOME OF
THE STORMS THIS AFTERNOON WERE PRODUCING ONE HOUR RAINFALL AMOUNTS OF
1 TO 2 INCHES PER HOUR.  WILL GO WITH A FLOOD WATCH AREA-WIDE TONIGHT
AND FRIDAY...THEN OVER THE COASTAL COUNTIES FRIDAY EVENING.  ACCORDING
TO THE GFS...THE PREFRONTAL TROUGH SHOULD CLEAR THE COAST BETWEEN 00Z
AND 03Z TOMORROW EVENING.  EXPECT THE HEAVY RAINFALL THREAT TO END AT
THAT TIME.  RAINFALL COVERAGE LOOKS TO BE GOOD...AND WILL KEEP THE
POPS ABOUT THE SAME AS THE CURRENT NUMBERS FOR TONIGHT THROUGH FRIDAY
NIGHT EXCEPT TO TWEAK THE FRIDAY NIGHT POPS DOWN A BIT IN THE NORTH
FRIDAY NIGHT.  THE MAIN SHORTWAVE TROUGH PUSHES INTO SE TX FRIDAY
NIGHT AND SATURDAY BUT WITH VERY LITTLE VORTICITY ADVECTION.

TEMPERATURES WILL BE A BIT OF A CHALLENGE.  A COMPROMISE BETWEEN THE
FWC AND MAV LOOK GOOD TONIGHT AND FRIDAY.  FRIDAY NIGHT THE SITUATION
GETS A BIT MORE COMPLEX.  THE MAV IS AN OUTLIER BETWEEN THE MET AND
FWC FOR THE THIRD PERIOD.  THE MID 60S LOOK BETTER FOR SATURDAY
NIGHT AFTER THE DRIER AIR FILTERS SOUTHWARD.  THE MAV IS ALSO A BIT
FAST WITH CLEARING OUT THE CLOUD COVER...AND WILL NOT DEVIATE FROM
THE CURRENT FORECAST IN THAT REGARD.

GMZ330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-227-
235>238-121630-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1016 PM CDT THU SEP 11 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

...FLASH FLOOD WATCH IN EFFECT FOR SOUTHEAST TEXAS AND ISOLATED
SEVERE STORMS POSSIBLE OVER SOUTHWESTERN PORTIONS OF SOUTHEAST
TEXAS...

.DAY ONE...TONIGHT.
HEAVY RAINFALL EXPECTED ACROSS SOUTHEAST TEXAS TONIGHT. A FLASH
FLOOD WATCH IS IN EFFECT THROUGH FRIDAY.

ISOLATED SEVERE THUNDERSTORMS MAY OCCUR OVER AREAS SOUTHWEST OF A
BELLVILLE TO WHARTON TO SARGENT LINE. SLIGHTLY DRIER AIR WILL
MOVE IN FROM THE SOUTHWEST AND MODERATE WIND SHEAR IN THE LOWER
ATMOSPHERE MAY SUPPORT THUNDERSTORMS CAPABLE OF STRONG DAMAGING
WINDS...HAIL OR POSSIBLY ISOLATED TORNADOES.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.
SHOWERS AND THUNDERSTORMS WILL LIKLEY BE GOING ON ACROSS SOUTHEAST
TEXAS IN THE MORNING AND MORE EXPECTED TO DEVELOP OVER THE COAST AND
SPREAD INLAND EARLY THURSDAY MORNING. HEAVY RAINFALL WILL
ACCOMPANY SOME THE THE STORMS. THE RAIN WILL END FROM WEST TO EAST
ONCE THE FRONT CROSSES THE AREA EARLY ON SATURDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEED TONIGHT OR FRIDAY.