Flash Flood Warning 30, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
910 PM CDT TUE JUN 22 2004

.DISCUSSION..
UPPER LEVEL TROUGH WILL PERSIST OVER REGION AT LEAST FOR THE NEXT
FEW DAYS. 850 MB ANALYZED DATA INDICATE MOISTURE RIDGE OVER TEXAS
COASTAL PLAINS WITH DEWPOINTS IN THE MID TEENS (C). SURFACE FRONTAL
BOUNDARY JUST NORTH OF CWFA WHILE MESO-HIGH HANGING OVER SW ZONES.
CONFLUENT FLOW EVIDENT ACROSS COASTAL ZONES DUE TO SOUTHEAST FLOW
ACROSS COASTAL REGION AND MESO-HIGH JUST NORTH. CONVECTION HAS BEEN
FIRING THIS EVENING UP NEAR AND ALONG THIS CONFLUENT ZONE.
MEANWHILE...SOUNDINGS CONTINUE TO INDICATE HIGH PWATS NEAR 2 INCHES
OVER CWFA. MESO-HIGH EXPECTED TO WEAKEN LATER TONIGHT SETTING THE
STAGE FOR A MORE UNSTABLE AIR MASS OVER REGION. CURRENT FORECAST
PACKAGE ON TRACK. NO CHANGES TO ZFPHGX AND CWFHGX. FLOOD WATCH
REMAINS IN EFFECT FOR ALL OF SOUTHEAST TEXAS TONIGHT THROUGH 6 PM
WEDNESDAY.

37/42/31
&&

.PREVIOUS DISCUSSION...
THE FLOOD POTENTIAL WILL BE THE MAIN FORECAST CHALLENGE FOR SE TX
TONIGHT INTO WEDNESDAY.  MODELS ARE FAIRLY CLOSE DURING THIS PERIOD
AND FORECAST PW/S OF 1.8 TO 2.3 INCHES...A SURFACE BOUNDARY ALONG THE
FAR NORTHERN COUNTIES...A SERIES OF SHORTWAVE TROUGHS AT 500 MB...AND
DIFFLUENT FLOW AT 200 AND 300 MB.  A WATER VAPOR LOOP OVER THE LAST
TWO DAYS SHOWS TROPICAL MOISTURE CONVERGING OVER TEXAS SINCE LAST
EVENING.  ANOTHER AREA OF MOISTURE LOOKS TO BE POOLING ALONG THE
SOUTHERN MEXICAN COAST AND MAY AGAIN PUSH NORTHWARD.  A CRUDE
EXTRAPOLATION OF THIS FEATURE AND MODEL TIMING OF THE BEST VORTICITY
ADVECTION WITH THE HIGHEST PW/S INDICATE THAT THE HEAVIEST RAINFALL
POTENTIAL WILL BE MAINLY OVERNIGHT TONIGHT INTO WEDNESDAY EVENING.
THERE SHOULD BE A BRIEF BREAK AFTER THE INITIAL LINE MOVES THROUGH
THIS AFTERNOON...YET SATELLITE AND RADAR SHOW REDEVELOPMENT SOUTHWEST
OF SAN ANTONIO.  THUS...EXPECT THE COASTAL AREAS TO HAVE RAIN LATE
THIS AFTERNOON AND REDEVELOPMENT AREA WIDE THIS EVENING.

BEYOND WEDNESDAY...THE MODEL SOLUTIONS DIVERGE.  THE ETA BEGINS TO DRY
THINGS OUT.  HOWEVER...THE GFS DEVELOPS A SURFACE LOW AND BRINGS A
SLUG OF MOISTURE OVER THE AREA AGAIN THURSDAY (PW/S OVER 2 INCHES).
BECAUSE OF THE UNCERTAINTY...WILL KEEP THE REMAINDER OF THE CURRENT
FORECAST IN PLACE BEGINNING THURSDAY.

WILL EXTEND THE FLOOD WATCH TO INCLUDE THE COASTAL COUNTIES IN AREA
AND THROUGH WEDNESDAY IN TIME.  WILL ALSO KEEP THE CAUTION IN PLACE
FOR THE GULF MARINE AREAS.

PL-40
41

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
FFA SE TX TXZ163-164-176>179-195>200-210>214-226-227-235>238.
SCEC 00 TO 60 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL.

&&

.POINT TEMPS/POPS...
COLLEGE STATION (CLL) 74 85 74 90 74 / 70 70 40 50 30
HOUSTON(IAH)          73 87 74 89 74 / 70 70 40 60 40
GALVESTON (GLS)       79 87 78 87 79 / 70 70 40 60 40

&&

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.