Severe Thunderstorm Warning 124, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
WEATHER SERVICE HOUSTON/GALVESTON TX
800 PM CST WED DEC 18 2002

FRONT IS APPROACHING THE NW ZONES THIS EVENING WITH DW PT GRADIENT
OF 15 TO 20 DEGREES ACROSS THE BOUNDARY. FRONT IS EXPECTED TO MOVE
ACROSS THE REGION TONIGHT AND REACH THE COAST DURING THE EARLY
MORNING HOURS. APPEARS CURRENT FORECAST IS IN PRETTY GOOD SHAPE.
AGREE WITH SPC THAT SE TX REMAINS UNDER THE GUN FOR SVR TSTMS
TONIGHT AS MID/UPPER LEVEL ENERGY IS STILL APPROACHING FROM THE WEST
AND ATMOSPHERE IS UNSTABLE WITH LOW LEVEL HELICITY VALUES SUPPORTING
SUPER CELL DEVELOPMENT. COMPLICATED PART OF THE FORECAST IS THE
LOW-MID LEVEL CAP OVER THE FA. BELIEVE AS THE BOUNDARY MOVES ACROSS
THIS WILL AID IN TSTM DEVELOPMENT AS SFC CONVERGENCE COUPLED WITH
INCREASING SYNOPTIC SCALE LIFT PROVIDE THE ADDITIONAL LIFT NEEDED TO
GET THROUGH THE CAP...ESPECIALLY NORTHERN ZONES. ACROSS THE EXT
SOUTHERN ZONES...CAP WILL LIKELY BE TOO STRONG...SO WILL ADJUST POPS
SLIGHTLY DOWNWARD ACROSS THIS ZONE. WILL RAISE POPS ACROSS THE
NORTHERN AND CENTRAL ZONES. WILL NUDGE LOW TEMPS SLIGHTLY LOWER
BASED ON LATEST MAV GUIDANCE.

FOR MARINE AREA...PROLONGED SOUTHERLY FLOW HAS RESULTED IN 10 FOOT
SEAS AT BUOY 019. EXPECT SWELLS TO PUSH SEAS TO AROUND 7 FEET ACROSS
THE 0-20 NM RANGE LATER TONIGHT. THEREFORE...WILL EXTEND SCA TO
NEARSHORE WATERS WITH THE EVE UPDATE.

.HGX...SCA 0 TO 60 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL.

33/41

UPDATED PRELIMS...
CLL BU 048/069 039/066 041 300
IAH BU 055/069 040/066 042 520
GLS BU 059/067 049/062 050 530
SW                         220
NE                         610

PREVIOUS DISCUSSION...
ARKLATEX REGION IS CURRENTLY UNDER A TORNADO WATCH (THRU 03Z). THIS
LOCATION IS WHERE GREATEST INSTABILITY IS EXPECTED TO DEVELOP THIS
AFTERNOON/TONIGHT AS A STRONG DISTURBANCE RAPIDLY APPROACHES THE
AREA FROM THE WEST. WITH THE CLOSE PROXIMITY OF THIS WATCH BOX AND
SPCS CURRENT PLACEMENT OF MODERATE AND SLIGHT RISK AREAS THROUGH
TONIGHT...WILL MENTION SOME STORMS POSSIBLE SEVERE IN THE FIRST
PERIOD OF OUR ZONES. PRECIP CHANCES LOOK TO REMAIN LOW (20% TO 30%)
BUT ANYTHING THAT DOES DEVELOP COULD POSSIBLE BECOME SEVERE.
GREATEST RISK AREA IS ACROSS OUR NORTHEAST COUNTIES. FRONTAL
BOUNDARY WILL MOVE ACROSS SOUTHEAST TEXAS TONIGHT AND WILL PASS OFF
THE COASTLINE AFTER SUNRISE TOMORROW. STORMS MAY DEVELOP ALONG THIS
BOUNDARY AND MAY STILL BE PRESENT AFTER SUNRISE...SO WILL KEEP SOME
POPS IN THE CENTRAL AND COASTAL ZONES. ENTIRE AREA WILL DRY OUT
DURING THE DAY. DRY CONDITIONS WILL PREVAIL ON FRIDAY AS SURFACE
HIGH PRESSURE SETTLES OVER TEXAS AND ON SATURDAY AS THE HIGH MOVES
OFF TO THE EAST. CURRENT THINKING IS THAT IT MAY BE TOO DRY ON
SATURDAY AND SATURDAY NIGHT FOR ANY SHOWERS OR THUNDERSTORMS TO
DEVELOP AS THE NEXT COLD FRONT APPROACHES. THIS BOUNDARY WILL MOVE
THROUGH THE AREA AND OFF THE COAST SATURDAY NIGHT. NEXT UPPER LOW
DEVELOPS OUT WEST OVER THE WEEKEND AND BEGINS ITS EASTWARD MARCH (OR
WILL IT BE A CRAWL?) NEXT WEEK. MODELS ARE SHOWING SOME SPEED AND
STRENGTH DIFFERENCES WITH THIS NEXT DISTURBANCE (SEE HPCS EXTENDED
FORECAST DISCUSSION...PMDEPD...FOR MORE DETAILS ON THESE
DIFFERENCES). THE POTENTIAL IS THERE FOR THIS SYSTEM TO BE OUR NEXT
HEAVY RAIN PRODUCER FOR PORTIONS OF SOUTHEAST TEXAS. FOR NOW...WILL
KEEP CHANCE POPS IN FOR MONDAY AND TUESDAY AND CALL FOR PARTLY
CLOUDY SKIES ON CHRISTMAS DAY.

FOR TEMPS...HAVE GENERALLY STUCK WITH THE MAV AND FMR OUTPUT. OUR
LAST DAY OF UNSEASONABLY WARM 70+ DEGREE AFTERNOONS (4TH IN A ROW)
WILL BE TODAY. EXPECT NEAR NORMAL TEMPERATURES TO RETURN TOMORROW
AND CONTINUE THROUGH THE UPCOMING WEEKEND.

42/35

GMZ300-330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-
227-235>238-191300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
700 AM CST WED DEC 18 2002

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

...A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING
EAST OF A LINE FROM AUSTONIO TO GALVESTON...

.DAY ONE...
.TODAY...THERE IS A SLIGHT CHANCE OF SEVERE THUNDERSTORMS THIS
AFTERNOON ALONG AND EAST OF A LINE FROM AUSTONIO TO NEW WAVERLY TO
SEGNO.  TONIGHT A SLIGHT RISK FOR SEVERE THUNDERSTORMS WILL EXIST
ALONG AND EAST OF A LINE FROM AUSTONIO TO NEW WAVERLY TO GALVESTON.
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP AHEAD OF A COLD FRONT
LATER THIS AFTERNOON AND EVENING.  SOME OF THESE STORMS COULD BE
SEVERE BY LATE THIS AFTERNOON NORTH OF THE HOUSTON METRO AREA...THEN
THIS EVENING FROM THE HOUSTON METRO AREA SOUTHEAST TO THE COAST.

.DAYS TWO THROUGH SEVEN...
.THURSDAY THROUGH TUESDAY...HAZARDOUS WEATHER IS NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND TONIGHT.