Severe Thunderstorm Warning 18, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
338 AM CST TUE FEB 25 2003

...CORRECTED TO ADD CURRENT PRELIMS...

LONG WAVE TROUGH SITUATED OVER THE SOUTHWESTERN PORTION OF THE COUNTRY
WILL HAVE SHORTWAVE TROUGHS SHEAR OFF ACROSS THE SOUTHERN PLAINS AND
TEXAS THROUGHOUT THE FORECAST PERIOD.  THE TIMING AND STRENGTH OF
THESE EVENTS AS THEY EFFECT SE TX WILL BE THE MAIN FORECAST PROBLEM.
THE ETA SEEMED TO BE DOING A BETTER JOB THAN THE GFS...BUT BOTH LOOK
OKAY IN THE SHORT TERM KEEPING ISENTROPIC LIFT OVER SE TX THE FIRST
COUPLE OF PERIODS.

IN THE SHORT TERM...THE FORECAST PROBLEM CONCERNS THE ONGOING WINTER
WEATHER EVENT OVER THE NORTHWESTERN QUARTER OF THE FORECAST AREA WITH
THUNDERSTORMS ADDED TO THE MIX.  SEE THE MARINE AND AVIATION
DISCUSSION BELOW CONCERNING THE THUNDERSTORM POSSIBILITIES.  FOR THE
THE FREEZING RAIN CHANCES...CURRENT RADAR AND SATELLITE TRENDS
INDICATE THAT THE BULK OF THE PRECIPITATION WILL BE MOVING EAST OF THE
ADVISORY AREA BY 14Z.  THE ETA BUFR FORECAST SOUNDINGS INDICATE
FREEZING RAIN OR DRIZZLE STILL A POSSIBILITY UNTIL 16Z.  THE QUESTION
WILL BE THE EXTENT OF THE ADVISORY AREA.  CURRENT MSAS ANALYSIS
INDICATES WET BULBS TO BE AT OR BELOW ZERO AT THE SURFACE FROM NEAR
MADISONVILLE TO SOMERVILLE AND CLIPPING THE FAR WESTERN EDGE OF
COLORADO COUNTY.  AM EXPECTING THIS AREA TO ADVECT EASTWARD SOME...AND
THE CURRENT ADVISORY AREA LOOKS OKAY THROUGH 16Z...MAINLY TO TAKE INTO
ACCOUNT ANY FREEZING DRIZZLE THAT OCCURS AFTER THE MAIN PRECIPITATION
AREA MOVES EAST.  THE GFS AND ETA BOTH INDICATE GOOD ISENTROPIC LIFT
WITH LOW CONDENSATION PRESSURE DEFICITS ON THE 295K SURFACE FOR THIS
MORNING.

RAIN CHANCES LOOK TO DECREASE OVER THE NORTH TODAY BUT STAY IN THE
LIKELY CATEGORY OVER THE COASTAL THIRD.  THE ISENTROPIC FORECAST
INDICATES CHANCE POPS TONIGHT...THEN LIKELY POPS AGAIN WEDNESDAY.  BY
THURSDAY THE FRONT OFFSHORE UNDERGOES SOME CYCLOGENISIS AND PULLS
SOME DRY AIR INTO THE AREA...BRIEFLY.  GIVEN THE MODEL
UNCERTAINTIES...WILL NOT CHANGE THE FORECAST BEYOND THURSDAY.

MARINE AND AVIATION DISC...
STRONG OFFSHORE FLOW WILL STRENGTHEN THIS MORNING SUPPORTING THE
CONTINUATION OF THE SCA... WILL SPLIT THE DIFFERENCE BETWEEN ETA AND
AVN FOR WINDS WEDNESDAY AND THURSDAY OFFSHORE. SHOWERS AND
THUNDERSTORMS WILL MOVE THROUGH IAH/HOU/GLS TERMINALS THIS MORNING ON
THE NOSE OF THE UPPER JET AND COINCIDENT WITH VERY MINIMAL ELEVATED
CAPE...COULD SEE SOME SMALL HAIL. THESE SHOULD BE ENDING BY 15Z. CIGS
SHOULD REMAIN 800 TO 1800 FT RANGE FOR MOST OF THE DAY...INCREASING
THREAT OF PRECIP TONIGHT SHOULD MOISTEN THE LOW-LEVEL FURTHER AND
LOWER CIGS OVERNIGHT INTO IFR CONDITIONS. 45

PL-40
45

.HGX...WINTER WEATHER ADVISORY NORTH OF A LINE FROM COLUMBUS TO
       BRENHAM TO HUNTSVILLE TO GROVETON UNTIL 16Z.
       SCA GALVESTON AND MATAGORDA BAYS.
       SCA 00 TO 60 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL.

PRELIMS...
CLL ER 038/035 042/039 055 536
IAH RR 042/039 046/041 055 757
GLS RR 049/046 050/047 055 757

TXZ163-164-176>179-195>200-210>214-226-227-235>238-251300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1000 PM CST MON FEB 24 2003

...WINTER WEATHER ADVISORY IN EFFECT FOR NORTHERN AND WESTERN
PORTIONS OF SOUTHEAST TEXAS...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

.DAY ONE...TONIGHT.
A WINTER WEATHER ADVISORY IS IN EFFECT FOR NORTHERN AND WESTERN
PORTIONS OF SOUTHEAST TEXAS GENERALLY ALONG AND NORTH OF A LINE FROM
COLUMBUS TO BRENHAM TO HUNTSVILLE TO GROVETON. FREEZING RAIN IS
POSSIBLE ACROSS THE ADVISORY AREA OVERNIGHT...MAINLY BETWEEN
MIDNIGHT AND 8 AM. THE GROUND IS STILL FAIRLY WARM DUE TO THE RECENT
WARM WEATHER SO ICE ACCUMULATIONS SHOULD BE 1/4 INCH OR LESS.
ELEVATED STRUCTURES SUCH AS BRIDGES AND OVERPASSES WILL BE MORE
PRONE TO ICE ACCUMULATION...MAKING TRAVEL POTENTIALLY TREACHEROUS.
FURTHER SOUTH...PRECIPITATION WILL BE IN THE FORM OF RAIN.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.
FOR TUESDAY...FREEZING RAIN WILL BE POSSIBLE IN THE ADVISORY AREA
UNTIL MID MORNING WHEN TEMPERATURES WARM ABOVE FREEZING. WEDNESDAY
THROUGH SUNDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.