Flash Flood Warning 46, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
859 PM CDT THU SEP 19 2002

A COMBINATION OF A STRONG COLD FRONT AND SHORTWAVE TROUGHS AHEAD OF
THE MAIN UPPER TROUGH WILL PROVIDE FOR THUNDERSTORMS ACROSS SE TX
TONIGHT.  THE MAIN PROBLEM CONCERNS RAINFALL AMOUNTS...POPS...AND
STRENGTH OF STORMS.  THE 18Z AVN LOOKS TO BE THE BEST MODEL WITH THE
00Z RUC AGREEING.  BOTH BRING THE COLD FRONT THROUGH CLL BY 06Z...IAH
AND THE COASTAL AREAS NEAR MATAGORDA BY AROUND 09Z OR 10Z...AND THE
UPPER COAST AROUND 12Z.

THE 01Z SURFACE ANALYSIS SHOWED THE FRONT THROUGH A KACT TO KSAT
LINE...WHILE A TROUGH WAS FROM KBPT TO JUST EAST OF KLBX.  AN MCS
FORMED OVER EASTERN HARRIS AND LIBERTY COUNTIES EARLIER AND CONVECTION
HAS CONTINUED TO FIRE ALONG THE SURFACE TROUGH OVER CHAMBERS AND
NORTHERN GALVESTON COUNTIES.  HEAVY RAINFALL CONTINUES TO BE A
THREAT...RAINFALL RATES BETWEEN 8 AND 9 PM HERE AT THE OFFICE HAS BEEN
FROM 2 TO 3 INCHES PER HOUR.  THIS IS REASONABLE GIVEN THE PW/S AND
MOISTURE ALOFT.  THE PW OF 2.54 INCHES AT LCH MAY BE A BIT SUSPECT
GIVEN THE SOUNDING WAS SATURATED BETWEEN 900 AND 775 MB...YET CRP WAS
AT 2.60.  THESE VALUES ARE AT OR ABOVE THE MAXIMUM FOR THE HISTORICAL
DATA FOR THIS DATE.  DEWPOINTS IN EXCESS OF 8 AT 700 MB AND 18 AT 850
MB WERE RIGHT ALONG THE UPPER TX COAST.  OTHER CONVECTION WAS FIRING
OVER THE MID TEXAS COAST IN ASSOCIATION WITH A SHORTWAVE TROUGH
EVIDENT ON THE 850...700...AND 500 MB SURFACES.  THESE STORMS SHOULD
AFFECT MAINLY THE COASTAL COUNTIES.  FEEL THAT THE THREAT FOR HEAVY
RAINFALL WILL BE OVER THE COASTAL COUNTIES...INCLUDING HARRIS AND
LIBERTY COUNTIES...AND NOT THE CENTRAL OR WESTERN COUNTIES.  THE
SEVERE THREAT LOOKS TO BE DIMINISHED.  WILL UPDATE TO MAKE THESE
CHANGES AND TO LOWER POPS OVER THE INLAND COUNTIES.

PL-40
43

.HGX...NONE.

TXZ163-164-176>179-195>200-210>214-226-227-235>238-200900-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
330 PM CDT THU SEP 19 2002

...SEVERE THUNDERSTORMS AND LOCALLY HEAVY RAINFALL POSSIBLE
THROUGH TONIGHT...

A MOIST AND UNSTABLE AIRMASS IN PLACE OVER SOUTHEAST TEXAS...AND A
PASSING UPPER LEVEL DISTURBANCE WILL RESULT IN THE CONTINUING
DEVELOPMENT OF SHOWERS AND THUNDERSTORMS OVER THE REGION. A COLD FRONT
WILL APPROACH THE REGION FROM THE WEST. THE FRONT IS EXPECTED TO
ENTER THE WESTERN PORTIONS OF SOUTHEAST TEXAS DURING THE LATE EVENING
HOURS AND REACH THE COAST DURING THE EARLY MORNING HOURS ON FRIDAY.
AHEAD OF THE FRONT...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
DEVELOP AND MOVE NORTHWARD. A LINE OF THUNDERSTORMS IS EXPECTED
TO DEVELOP NEAR AND ALONG THE FRONT. AS THIS LINE OF THUNDERSTORMS
MOVES ACROSS SOUTHEAST TEXAS TONIGHT...THERE WILL BE A THREAT OF LARGE
HAIL AND STRONG DAMAGING WINDS.

RAINFALL AMOUNTS OF 1 TO 2 INCHES CAN BE EXPECTED OVER MUCH OF
THE AREA THROUGH TONIGHT AS UPPER LEVEL DISTURBANCES AND
THE FRONTAL BOUNDARY INTERACT WITH TROPICAL MOISTURE OVER SOUTHEAST
TEXAS. LOCALIZED RAINFALL AMOUNTS OF 3 TO 5 INCHES ARE POSSIBLE.

STAY TUNED TO NOAA WEATHER RADIO OR OTHER WEATHER NEWS SOURCES FOR
LATER STATEMENTS CONCERNING THIS SEVERE WEATHER AND HEAVY RAIN THREAT.