Flash Flooding in Texas, June 22 to 23, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1027 AM CDT TUE JUN 22 2004

.DISCUSSION...
AN MCS WAS MOVING INTO THE WESTERN COUNTIES OF SE TX LATE THIS
MORNING.  THE FORECAST PROBLEM OF THE DAY IS RAINFALL AND SEVERE
POTENTIAL.

THE UPPER LEVEL ANALYSES FOR 12Z INDICATED VERY GOOD DIFFLUENCE AT 200
AND 300 MB COUPLED WITH SHORTWAVE TROUGHS AT 500 AND 700 MB AND VERY
GOOD MOISTURE ADVECTION AT 700 AND 850 MB.  THE CRP AND LCH SOUNDINGS
HAD PW/S OF 2.0 AND 1.6 INCHES RESPECTIVELY AND THE ACARS/MAP SOUNDING
FOR CLL JUST AHEAD OF THE STORMS AT 14Z HAD A PW OF 1.8 INCHES.  FOR
CRP...THE PW IS JUST BELOW 2 STANDARD DEVIATIONS FOR THIS DATE.  EVEN
THOUGH THAT WOULD INDICATE A MARGINAL FLASH FLOOD POTENTIAL...FEEL
THAT THE PW WILL INCREASE LATER THIS AFTERNOON AND TONIGHT PER THE
ETA12.  THE DYING MCS WILL HAVE ISOLATED POTENTIAL FOR FLASH FLOODING
THROUGH MIDDAY...YET ITS MAIN EFFECT WILL BE TO ADD WATER TO THE
GROUND AHEAD OF THE EXPECTED RAINFALL THAT SHOULD DEVELOP THROUGHOUT
THE AFTERNOON AND TONIGHT.  THE GFS AND ETA FORECAST A SERIES OF
SHORTWAVE TROUGHS THAT WILL HELP FOCUS THE MOISTURE STREAMING OFF THE
GULF OF MEXICO THROUGH TONIGHT.  THE MODELS ALSO KEEP THE UPPER LEVEL
DIFFLUENCE IN PLACE DURING THE TIME PERIOD.  ALSO WITH THE DYING
MCS...THE SEVERE POTENTIAL HAS BEEN DROPPING.  THAT POTENTIAL
REMAINS...YET WILL STICK WITH THE LOCALLY HEAVY RAINFALL IN THE PUBLIC
FORECAST AS THE HAZARDOUS WEATHER OUTLOOK DEALS WITH THE SLIGHT RISK
OF SEVERE STORMS.

TEMPERATURES TODAY WILL BE IMPACTED BY THE CLOUD COVER....ESPECIALLY
IN THE WESTERN TWO-THIRDS OF THE AREA.  WILL LOWER THESE IN THE
UPDATE.  WILL ALSO TWEAK THE WINDS UP A BIT OVER THE LAND AND COASTAL
WATERS.

PL-40
41

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
FFA SE TX INLAND COUNTIES TXZ163-164-176>179-195>200-210>213-226-227.
SCEC 00 TO 60 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
700 AM CDT TUE JUN 22 2004

TXZ163-164-176>179-195>200-210>214-226-227-235>238-231200-
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-GALVESTON-
GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-MADISON-MATAGORDA-MONTGOMERY-
POLK-SAN JACINTO-TRINITY-WALKER-WALLER-WASHINGTON-WHARTON-
700 AM CDT TUE JUN 22 2004

...HEAVY RAINFALL EVENT EXPECTED ACROSS SOUTHEAST TEXAS TODAY
THROUGH WEDNESDAY...
...FLOOD WATCH HAS BEEN ISSUED FOR ALL BUT THE COASTAL COUNTIES OF
SOUTHEAST TEXAS THIS AFTERNOON AND TONIGHT...

.DAY ONE...TODAY AND TONIGHT.
AN APPROACHING UPPER LEVEL DISTURBANCE WILL COMBINE WITH A MOIST AND
UNSTABLE AIRMASS TO PRODUCE NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS
SOUTHEAST TEXAS TODAY AND TONIGHT. LOCALLY HEAVY RAINFALL WILL BE
POSSIBLE...WHICH COULD LEAD TO FLOODING PROBLEMS OVER THE INLAND
COUNTIES.

RAINFALL AMOUNTS THROUGH TONIGHT WILL AVERAGE 1 TO 2 INCHES...WITH
ISOLATED TOTALS OF 3 TO 5 INCHES POSSIBLE. THIS HEAVY RAINFALL COULD
LEAD TO PONDING OF WATER ON ROADWAYS OR MORE SIGNIFICANT FLOODING
PROBLEMS.

MOTORISTS SHOULD USE EXTREME CAUTION WHILE TRAVELING TODAY AND
TONIGHT. DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS
THE ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO
CROSS SAFELY. VEHICLES CAUGHT IN RISING WATER SHOULD BE ABANDONED
QUICKLY. IF YOUR VEHICLE STALLS...ABANDON IT AND SEEK HIGHER GROUND
IMMEDIATELY. RAPIDLY RISING WATER MAY ENGULF YOUR VEHICLE AND ITS
OCCUPANTS AND SWEEP THEM AWAY.

A FEW ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE TODAY WHICH COULD
PRODUCE LARGE HAIL OR DAMAGING WINDS. HOWEVER...THE OVERALL RISK
OF SEVERE WEATHER IS MINIMAL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

WEDNESDAY AND WEDNESDAY NIGHT...A STATIONARY FRONT JUST NORTH OF THE
AREA AND DEEP MOISTURE IN PLACE WILL COMBINE TO PRODUCE MORE SHOWERS
AND THUNDERSTORMS ACROSS SOUTHEAST TEXAS. ADDITIONAL RAINFALL TOTALS
OF 1 TO 3 INCHES OF RAINFALL...WITH LOCALLY HIGHER AMOUNTS...WILL BE
POSSIBLE.

THURSDAY...AN UPPER LEVEL DISTURBANCE MAY BRING ANOTHER ROUND OF
THUNDERSTORMS AND HEAVY RAINFALL TO SOUTHEAST TEXAS.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS POSSIBLE TODAY OR TONIGHT.