Severe Thunderstorm Warning 121, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
745 AM CST THU DEC 12 2002

UPDATED: HAVE ISSUED AN SCA FOR 20-60 AS LOW PRESSURE OVER THE LOWER
COAST CONTINUES TO DEEPEN.

STRONG SHORTWAVE LOCATED JUST SOUTH OF BIG BEND EARLY THIS MORNING
WILL BRING A QUICK ROUND OF TSRA TO SE TX TODAY. ANALYSIS SHOWS SFC
LOW/WARM FRONT HAVE DEVELOPED OVER THE COASTAL WATERS WITH DEWPOINTS
IN THE MID/UPPER 60S SOUTH OF THE FRONT. RAPID INCREASE IN MOISTURE
WILL OCCUR NEXT FEW HOURS AS 30-40 KT LLJ TRANSPORTS PWS OF 1.1-1.3
INCHES ACROSS CWA BY 18Z. SHRA INCREASING OVER CENTRAL/SRN ZONES
ALREADY IN WAA PATTERN AND EXPECT SIGNIFICANT INCREASE IN ACTIVITY
JUST AFTER 12Z AS LIFT FROM APPROACHING SHORTWAVE BEGINS TO IMPACT
AREA. WILL WORD LIKELY POPS NRN ZONES...CATEGORICAL CENTRAL/SOUTH
TODAY. MAIN QUESTION FOR TODAY IS SEVERE POTENTIAL. LATEST GFS/ETA
DIFFER ON TRACK OF SFC LOW...WITH 06Z ETA BRINGING LOW AND DEEPER
INSTABILITY ONSHORE COASTAL COUNTIES AROUND MIDDAY. THINKING WARM
FRONT WILL REMAIN OFFSHORE...KEEPING ONLY MARGINAL UNSTABLE AIRMASS
IN PLACE OVER SRN ZONES (LIS 0 TO -2). 850-700 MB LAPSE RATES
STEEPEN THROUGH THE DAY AND WET-BULB ZEROS WILL FALL TO AROUND 8000
FT THIS AFTN SUPPORTING A HAIL THREAT WITH ELEVATED CONVECTION. WILL
GO AHEAD AND MENTION SEVERE CENTRAL/SRN ZONES PER SPC DAY 1 OUTLOOK.
SHOULD WARM FRONT MOVE ONSHORE COASTAL COUNTIES...DAMAGING WIND
GUSTS OR EVEN ISOLATED TORNADOES WOULD BE POSSIBLE WITH SFC BASED
CONVECTION.

PRECIP WILL END OVER WRN ZONES LATE AFTN AND ERN ZONES
EARLY EVENING AS SHORTWAVE PASSES OVER AREA. RAPID DRYING WILL OCCUR
TONIGHT AS PACIFIC AIRMASS SURGES ACROSS CWA.

STILL LOOKS LIKE A GREAT WEEKEND AHEAD AS SFC HIGH SETTLES OVER CWA.
DRY AIRMASS WILL SUPPORT WIDE DIURNAL RANGE WITH WARMER MAX TEMPS
EXPECTED. ONSHORE FLOW RETURNS LATE SUNDAY. MODELS HAVE TRENDED
TOWARD LESS MOISTURE RETURN WITH NEXT SYSTEM TO AFFECT SE TX
MON/TUE...SO WILL KEEP WITH ONLY SLIGHT CHANCE POPS.

35/43/46

.HGX...SCEC 0 TO 20 NM OFFSHORE HI ISLAND TO MATAGORDA SHIP CHANNEL.
       SCA 20-60 HI ISL TO MATA SHIP CHANNEL
PRELIMS...
CLL TU 059/041 061/037 062 710
IAH TU 062/043 063/038 064 920
GLS TU 066/050 062/046 061 930

GMZ300-330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-
227-235>238-131300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
700 AM CST THU DEC 12 2002

...RISK OF SEVERE STORMS OVER THE SOUTHERN HALF OF SOUTHEAST TEXAS
TODAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS AND THE UPPER
TEXAS COASTAL WATERS.

.DAY ONE...
.TODAY...AN UPPER LEVEL STORM SYSTEM WILL MOVE ACROSS SOUTHEAST TEXAS
TODAY AND COMBINE WITH AN INCREASINGLY MOIST AIRMASS TO PRODUCE
SHOWERS AND THUNDERSTORMS. SOME STORMS MAY BECOME SEVERE SOUTH OF A
LINE FROM COLUMBUS TO CONROE TO MOSS HILL. THE PRIMARY SEVERE WEATHER
THREAT WILL BE LARGE HAIL DUE TO COLD AND DRY AIR IN THE MID LEVELS OF
THE ATMOSPHERE. HOWEVER...DAMAGING WIND GUSTS AND ISOLATED TORNADOES
ARE ALSO POSSIBLE OVER THE COASTAL COUNTIES.

THE THUNDERSTORMS WILL END QUICKLY FROM WEST TO EAST BY EARLY
EVENING.

.DAYS TWO THROUGH SEVEN...
.FRIDAY THROUGH WEDNESDAY...HAZARDOUS WEATHER IS NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL BE POSSIBLE TODAY.

TXZ199-200-210>214-226-227-235>238-121700-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
530 AM CST THU DEC 12 2002

...SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR THE SOUTHERN HALF OF
SOUTHEAST TEXAS UNTIL 11 AM THIS MORNING...

THE STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH
UNTIL 11 AM CST FOR THE FOLLOWING COUNTIES: AUSTIN...BRAZORIA...
CHAMBERS...COLORADO...FORT BEND...GALVESTON...HARRIS...JACKSON...
LIBERTY...MATAGORDA...MONTGOMERY...WALLER...WHARTON.

THE COMBINATION OF AN INCREASINGLY UNSTABLE AIRMASS AND AN APPROACHING
UPPER LEVEL DISTURBANCE WILL PRODUCE NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS THE SOUTHERN HALF OF SOUTHEAST TEXAS THIS
MORNING. SOME OF THESE STORMS COULD BECOME SEVERE. THE PRIMARY SEVERE
WEATHER THREAT WILL BE LARGE HAIL...WITH DAMAGING DOWNBURST WINDS ALSO
POSSIBLE.

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.  SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE
TORNADOES.

STAY TUNED TO NOAA WEATHER RADIO OR OTHER WEATHER NEWS SOURCES FOR
FURTHER UPDATES AND POSSIBLE WARNINGS.