Tornado Warning 30, NWS Houston/Galveston, TX

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

RAINFALL AMOUNT AND COVERAGE THE MAIN CHALLENGE OF THE DAY.  THE 12Z
SOUNDINGS...FWD/LCH/CRP...INDICATED A FAIRLY MOIST AND UNSTABLE
ATMOSPHERE OVER SE TX.  LI/S WERE BETWEEN -6 AND -9...THE K INDEX FROM
30 TO 45...AND CAPES FROM 3100 TO 5050.  THE ACARS/MAPS SOUNDING AT
IAH FOR 13Z SHOWED A BIT MORE STABLE SITUATION WITH THE LI AT -3...K
INDEX AT 30...AND CAPE AT 2124.  AM A BIT CONCERNED ABOUT THE HEAVY
RAINFALL ASPECTS FOR LATER TODAY OVER THE NORTHERN COUNTIES.  THE PW/S
FOR THE CRP AND LCH SOUNDINGS WERE UNDER THE 2 STANDARD DEVIATIONS
ACCORDING TO THE HISTORICAL MARK FOR A HEAVY RAINFALL THREAT FOR THIS
DATE. HOWEVER...THE FWD SOUNDING WAS ALMOST AT THE 2 STANDARD
DEVIATION MARK.  THE CURRENT RADAR AND SATELLITE DATA INDICATES THE
STORMS MOVING THROUGH N TX SHOULD STAY NORTH OF THE FORECAST AREA.
WILL REASSESS THE SITUATION AGAIN AROUND NOON AND UPDATE THE FORECAST
IF NEEDED AT THAT TIME FOR ANY HEAVY RAINFALL THREAT.

FOR NOW...THE MAIN RAINFALL WILL COME FROM THE SHOWERS AND
THUNDERSTORMS DEVELOPING ALONG THE COASTAL COUNTIES.  THE CURRENT
FORECAST LOOKS GOOD IN THIS REGARD...THOUGH WILL ADD THE POSSIBILITY
OF HEAVY RAINFALL.

PL-40
46

.HGX...NONE.

PRELIMS...
CLL TT 089/073 081/068 086 678
IAH TT 087/075 083/070 085 658
GLS TT 087/080 084/075 084 657

PREV DISC...
JUICY AIRMASS REMAINS IN PLACE OVER SE TX. EXPECT SHRA/TSTMS TO
INCREASE OVER THE GULF WITHIN THE NEXT COUPLE HOURS AND GRADUALLY
SPREAD INLAND THROUGHOUT THE DAY AS CONVECTIVE TEMPS IN THE MID 80S
ARE REACHED. DIFLUENCE ALOFT BECOMES FURTHER ESTABLISHED LATER THIS
AFTERNOON ALLOWING FOR INCREASED COVERAGE COMPARED TO YDAY. WILL
KEEP LIKELY POPS ALREADY IN THE FCST IN PLACE.

HEAVY RAIN EVENT SETTING UP LATE TONIGHT THROUGH EARLY SAT MORNING.
COOL FRONT EXPECTED TO EITHER STALL OR SLOW DOWN SIGNIFICANTLY
(DEPENDING ON YOUR MODEL OF CHOICE) DURING THIS TIME PERIOD AS IT
APPROACHES SE TX. ETA IS SLOWER THAN MOST OTHER MODELS...HOLDING THE
H5 TROF TO OUR WEST ABOUT 12-18 HOURS LATER THAN THE GFS, NOGAPS,
CANADIAN AND THE 12Z ECMWF. FOR THIS PACKAGE...WELL GO WITH THE
CONSENSUS GFS SOLN AS FAR AS TIMING GOES. PWS AROUND 2.2 POOL
ALONG THE FRONTAL BOUNDARY AND DYNAMICS ARE ALL THERE TOO:
IMPRESSIVE UPPER LEVEL DIFFLUENCE/JET POSITION, SPEED CONVERGENCE
ALONG THE UPPER TX COAST. EXPECT THE RAIN TO CONTINUE THROUGH MUCH
OF THE NIGHT ACROSS NW ZONES AND SPREAD ACROSS THE ENTIRE FA THRU
THE DAY FRIDAY AND FRIDAY NIGHT. AS OF NOW...WERE EXPECTING RAIN TO
GRADUALLY END FROM NORTHWEST TO SOUTHEAST FRIDAY NIGHT AND INTO
SATURDAY MORNING. WILL ADD THE MENTION OF HEAVY RAINS TO THE ZONES
THIS MORNING BUT WILL LET THE DAY CREW DECIDE WHETHER TO ISSUE AN
FFA. WOULD NOT BE SURPRISED TO SEE LOCALIZED 6+ INCH AMOUNTS BY
SAT MORNING DUE TO THE LONGEVITY AND TRAINING NATURE OF THE
PRECIP...MAYBE MORE IF THE ETA SOLN VERIFIES.

COULD SEE A WIND SHIFT AS SHRA/TSTM COMPLEX PUSHES THRU FRI NT/SAT.
TEMPS WONT RESPOND THAT MUCH UNTIL HIGH PRESSURE SLIDING DOWN THE
ROCKIES FILTERS IN ON SUNDAY. DRIER AIR AND SEASONABLE TEMPS
EXPECTED THROUGH THE MIDDLE OF NEXT WEEK.

GULF IS QUIET FOR NOW. MAY NEED THE SCEC FLAGS FRI OR FRI NT AS
ONSHORE WINDS INCREASE.

47/30

GMZ330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-227-
235>238-121200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
705 AM CDT THU SEP 11 2003

...HEAVY RAINFALL EVENT TONIGHT THROUGH EARLY SATURDAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT.
TODAY...SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO DEVELOP TODAY AS TEMPERATURES WARM INTO THE 80S. LOCALIZED 2 INCH
RAINFALL AMOUNTS ARE POSSIBLE.

TONIGHT...AN UPPER LEVEL STORM SYSTEM AND A SLOW MOVING COLD FRONT
WILL BEGIN APPROACHING SOUTHEAST TEXAS. EXPECT NUMEROUS SHOWERS AND
THUNDERSTORMS TO PERSIST GENERALLY WEST OF A MADISONVILLE TO
COLUMBUS LINE DURING THE OVERNIGHT HOURS. TRAINING PRECIPITATION
COULD PRODUCE LOCALIZED 2 TO 3 INCH RAINFALL AMOUNTS OVER THIS AREA.
A FLOOD WATCH MAY BE REQUIRED.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.
THE STORM SYSTEM WILL CONTINUE TO SLOWLY MOVE INTO ALL OF SOUTHEAST
TEXAS FRIDAY AND INTO EARLY SATURDAY. NUMEROUS SHOWERS AND
THUNDERSTORMS ARE EXPECTED. DUE TO THE ABUNDANT MOISTURE AVAILABLE
AND THE SLOW MOVEMENT OF THE SYSTEM...WIDESPREAD 2 TO 4 INCH
RAINFALL ACCUMULATIONS ARE EXPECTED...WITH LOCALIZED AMOUNTS IN
EXCESS OF 6 INCHES POSSIBLE. THESE RAINFALL AMOUNTS COULD PRODUCE A
RISE ON AREA STREAMS AND RIVERS. AGAIN...A FLOOD WATCH MAY BE
REQUIRED.

THE RAIN WILL END FROM NORTHWEST TO SOUTHEAST LATE FRIDAY NIGHT INTO
MID DAY SATURDAY. HIGH PRESSURE WILL FILTER INTO THE REGION ON
SUNDAY BRINGING DRY WEATHER AND SEASONABLE TEMPERATURES THROUGH THE
MIDDLE OF NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED TONIGHT.