Severe Thunderstorm Warning 98, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
850 PM CDT THU JUN 21 2001

REGIONAL 88DS AND IR IMAGERY SHOW A LINE OF SHOWERS AND
THUNDERSTORMS JUST NORTHWEST OF OUR CWA...MOVING SOUTH-SOUTHEAST.
THE MAIN FORECAST ISSUE IS THE THREAT FOR HEAVY RAIN. THE LINE IS
PROPAGATING IN AN ORDERLY FASHION...ALTHOUGH 3HR PRESSURE CHANGE
FIELDS INDICATE ONLY WEAK PRESSURE RISES BEHIND THE LINE AND LAGGING
COLD FRONT.

THE 00Z RAOBS...GOES SOUNDER...AND 21Z RUC AGREE ON PWS AROUND 1.5
INCHES AREAWIDE EXCEPT FOR POOLING TO NEAR 1.8 INCHES NEAR THE LINE
OF STORMS. WARM CLOUD DEPTH IS 3-3.5 KM...0-6 KM MEAN WINDS ARE
WEAK...AND STORM MOTION SLOW...POINTING TO A HEAVY RAIN THREAT.
RAINFALL FROM ALLISON MAKES THIS MORE CRITICAL THAN NORMAL SINCE
ADDITIONAL RAINFALL WILL PRIMARILY BE RUNOFF. HOWEVER...WITHOUT A
SUSTAINED MODERATE TO STRONG MOIST AIR FEED...LOSS OF DAYTIME
HEATING...AND PROGRESSION OF CURRENT LINE...WILL NOT ISSUE A FLASH
FLOOD WATCH.

WILL RETAIN MENTION OF HEAVY RAIN IN THE FORECAST AND LEAVE SPS/HWO
AS IS. WILL UPDATE TO CATEGORICAL POPS EXCEPT ALONG THE COAST
WITH RAIN TRENDING OUT FROM NORTH TO SOUTH AND FROM LATE TO TOWARD
MORNING.

.HGX...NONE.

31/40/DO

UPDATE PRELIMS...
CLL BU 069/089 065/091 068 +10  INCREASED POPS TONIGHT
IAH BU 071/090 067/091 069 930  DITTO
GLS EB 077/087 075/087 077 541  DITTO