Flash Flood Warning 40, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
850 PM CST FRI DEC 12 2003

.DISCUSSION...
CONVECTION BECOMING BETTER ORGANIZED AS HIGHER LEVEL OF MOIST AND
MARGINALLY UNSTABLE AIR HAS ADVECTED INTO SOUTHEAST TEXAS FROM THE
GULF. INVERTED TROUGH...STRENGTHING WARM ADVECTION WITH LOW LEVEL
JET AND SHALLOW WARM FRONT/COASTAL TROUGH FROM SAN LUIS PASS WNW ALL
CONTRIBUTING TO FOCUS NEARLY SOLID LINE OF THUNDERSTORMS PRODUCING
HEAVY RAIN FROM CONROE SOUTH SOUTHWEST TO THE COAST IN MATAGORDA
COUNTY.   PROGRESSIVE TROUGH MOVING THROUGH WEST TEXAS SHOULD KEEP
THIS LINE MOVING EASTWARD WITH ALL BUT EXTREME EAST PART OF ARE AREA
SEEING HEAVY STUFF ENDING BY AROUND MIDNIGHT.  EXPECT 2 INCHES
WIDESPREAD WITH ISOLATED TOTALS TO AROUND 4 INCHES. FALLING FAST
ENOUGH OVER BROAD ENOUGH AREA FOR STREET FLOODING SO ISSUED AN URBAN
AND SMALL STREAM.  PROFILE SUGGEST SUFFICIENT SHEAR FOR ROTATION.
WHILE SOME WEAK ROTATION NOTED ON RADAR NO STORMS HAVE EXCEEDED
SEVERE THRESHOLDS.  PERHAPS THE INSTABILITY ISNT QUITE POTENT
ENOUGH. SEVERE THREAT SHOULD END WITH PASSAGE OF THIS LINE.

LIFT FROM ADVANCING TROUGH PRODUCING ENHANCED MID CLOUDS AND SOME
PRECIP BEHIND MAIN EVENT SO EXPECT PRECIP CHANCES TO CONTINUE MOST
OF THE NIGHT.  ONE OTHER THING TO CONSIDER...PATCHY DENSE FOG
FORMING OVER SOUTH TEXAS AND MIGHT HAVE SAME BRIEFLY BEFORE MAIN
WINDSHIFT AND DRIER AIR KICKS IN DURING THE PREDAWN HOURS.

MINOR CHANGES THIS UPDATE TO ACCOUNT FOR CURRENT TRENDS.
&&

.MARINE...
NO CHANGE FOR THE MARINE AREA ADVISORIES. WILL KEEP SCA FOR THE
OFFSHORE WATERS AND A CAUTION STATEMENT FOR THE BAYS. WIND SHIFT TO
OCCUR EARLY SUN MORNING ALONG THE COAST.
&&

.HGX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT SHOULD EXERCISE CAUTION BAYS
SMALL CRAFT ADVISORY 0-60NM
&&

30/43

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1050 AM CST FRI DEC 12 2003

TXZ163-164-176>179-195>200-210>214-226-227-235>238-131300-
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-
1050 AM CST FRI DEC 12 2003

...SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND TONIGHT...
...LOCALLY HEAVY RAINFALL POSSIBLE TONIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT.
AN UPPER LEVEL DISTURBANCE WILL APPROACH TEXAS TODAY FROM THE WEST.
SURFACE LOW PRESSURE WILL DEVELOP ALONG THE TEXAS COAST AND WILL
LEAD TO INCREASING SHOWER AND THUNDERSTORM CHANCES THIS AFTERNOON
AND TONIGHT. SOME OF THE THUNDERSTORMS MAY BECOME SEVERE DUE TO
INCREASINGLY FAVORABLE WIND SHEAR. DURING THE AFTERNOON HOURS...THE
SEVERE WEATHER THREAT IS PRIMARILY ISOLATED TORNADOES ACROSS THE
COASTAL AND CENTRAL PORTIONS OF SOUTHEAST. THIS THREAT WILL
CONTINUE INTO THE OVERNIGHT HOURS AND EXPAND TO THE NORTHERN PORTIONS
OF SOUTHEAST TEXAS WHERE LARGE HAIL WILL BE THE PRIMARY THREAT.
AS A COLD FRONT MOVES ACROSS SOUTHEAST TEXAS.

LOCALLY HEAVY RAINFALL WILL BE POSSIBLE ACROSS ALL OF SOUTHEAST
TEXAS TONIGHT WITH AVERAGE RAINFALL AMOUNTS OF 1 TO 2 INCHES EXPECTED
AND ISOLATED AMOUNTS OF UP TO 4 INCHES POSSIBLE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.
SHOWERS AND THUNDERSTORMS WILL GRADUALLY MOVE OFF TO THE EAST LATE
SATURDAY MORNING AS A COLD FRONT AND A DRIER AIRMASS MOVES EASTWARD
ACROSS THE STATE. FOR SATURDAY AFTERNOON THROUGH THURSDAY...
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON THROUGH EARLY
SATURDAY MORNING.