Severe Thunderstorm Warning 164, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1039 AM CST TUE DEC 4 2012

.UPDATE...
A QUICK UPDATE TO RAISE THE POPS FOR THE NORTH THIS MORNING AND
ELSEWHERE FOR THE AFTERNOON AS THE FRONT PUSHES SOUTH. AT 16Z THE
FRONT WAS NEAR A CORSICANA-TEMPLE-KERRVILLE LINE WITH MOST OF THE
SHOWER ACTIVITY ASSOCIATED WITH THE PREFRONTAL TROUGH WHICH IS
NEARING PALESTINE-HEARNE-SAN ANTONIO LINE. THE FRONT SHOULD
CONTINUE TO PUSH SOUTHEAST AND PROVIDE LIFT AS IT DOES SO AND WITH
THE ABUNDANT MOISTURE THAT HAS BEEN STREAMING INTO THE AREA
EXPECTING WIDESPREAD COVERAGE OF SHOWERS OVER THE REGION TODAY. AS
THE LIFTING WORKS SOUTH AND DAYTIME HEATING PROGRESSIVELY BECOMES
MORE AVAILABLE STORM ENVIRONMENT BECOMES MORE FAVORABLE FOR
THUNDERSTORMS WITH CAPE OF 800-2000J/KG THIS AFTERNOON. VERY POOR
SHEAR SO EXPECTING MULTICELL STORMS WITH POOR ORGANIZATION. THE
STORMS SHOULD BE MOVING OFFSHORE AROUND 6PM WITH STORMS OUT OVER
THE WATER BY 8PM.
45

&&

.DISCUSSION...

&&

.PREV DISCUSSION... /ISSUED 551 AM CST TUE DEC 4 2012/

DISCUSSION...
UPDATED AVIATION SECTION.

AVIATION...
DENSE FOG AT THE SOUTHERN TAF SITES THIS MORNING...INCLUDING
LBX...HOU AND SGR. THIS SHOULD BURN OFF OVER THE NEXT FEW HOURS
WITH CEILINGS LIFTING TO MVFR THEN VFR. MESOSCALE
MODELS...WRF...SUGGESTING FRONT...NOW WORKING ITS WAY FROM NW TO
SE ACROSS THE AREA...SHOULD BECOME A FOCUS FOR SHOWERS AND
THUNDERSTORMS MAINLY THIS AFTERNOON AND EARLY EVENING. THIS WILL
DEPEND ON SKY PARTIALLY CLEARING OUT AND THINK THIS SHOULD HAPPEN.
BASED ON THESE MODEL SOLUTIONS AND TIMING OF FRONT...THUNDERSTORM
THREAT SHOULD EXIT THE COAST NEAR OR JUST AFTER 00Z. TONIGHT AND
WEDNESDAY MUCH MORE BENIGN AVIATION CONDITIONS WITH MAINLY VFR
CONDITIONS ALTHOUGH CANT RULE OUT SOME PATCHY FOG TONIGHT IN AREAS
THAT GET RAIN. 46

PREV DISCUSSION... /ISSUED 520 AM CST TUE DEC 4 2012/

DISCUSSION...
SEE UPDATE BELOW.

UPDATE...
ISSUED A DENSE FOG ADVISORY VALID THROUGH 9 AM CST. LOCATIONS
MAINLY EAST OF HIGHWAY 59 AND SOUTH OF INTERSTATE 10 WERE
EXPERIENCING FOG WITH THE VISIBILITY LOWERING TO UNDER ONE HALF
MILE AT TIMES. EXPECT THE FOG TO LIFT AFTER SUNRISE AND BY 9 AM.

40

PREV DISCUSSION... /ISSUED 443 AM CST TUE DEC 4 2012/

DISCUSSION...
A COLD FRONT AND ASSOCIATED SHORTWAVE TROUGH WILL MOVE ACROSS SE
TX TODAY. THE MAIN FORECAST CHALLENGES OF THE DAY INCLUDE EARLY
MORNING FOG...RAINFALL COVERAGE THROUGHOUT THE DAY...AND STRENGTH
OF ANY THUNDERSTORMS THAT DEVELOP. LIKED THE GFS TIMING OF
EVENTS. THE COLD FRONT...OR ELSE WIND SHIFT...WILL MAKE ITS WAY
INTO THE WESTERN COUNTIES BY AROUND MIDDAY AND THEN TO NEAR THE
COAST BY AROUND 6 PM THIS EVENING.

THE FORECAST MODEL SOUNDINGS INDICATED PATCHY FOG WILL BE POSSIBLE
EARLY THIS MORNING. SOME SEA FOG WAS ALSO PRESENT IN AND AROUND
GALVESTON BAY WHERE SURFACE DEWPOINTS IN THE UPPER 60S WERE
PRESENT OVER WATER TEMPERATURES IN THE MID 60S. THE SOUNDINGS
FORECAST THE LOW-LEVEL INVERSION TO BREAK BY AROUND 9 AM. WILL
KEEP AN EYE OUT TO SEE IF ANY DENSE FOG DEVELOPS OVER THE LAND
AREAS AND MAY ISSUE AN ADVISORY LATER IF NEEDED.

THE MODELS SOUNDINGS ALSO SHOWED THAT THE BEST INSTABILITY WILL
BE OVER MOST OF THE CENTRAL AND EASTERN COUNTIES LATER THIS
MORNING THROUGH THE AFTERNOON. THE SOUNDINGS ALSO FORECAST A CAP
OVERHEAD THAT SHOULD BREAK DURING THE LATE MORNING PERIOD. THE
HIGH RESOLUTION MODELS DEVELOP ISOLATED SHOWERS THIS MORNING...
WITH SHOWERS AND THUNDERSTORMS DEVELOPING AHEAD OF THE FRONT AS IT
MOVES ACROSS THE FAR NORTHWESTERN SET OF COUNTIES DURING THE EARLY
AFTERNOON. THESE MODELS PUSH THE AREA OF STORMS INTO THE
INTERSTATE CORRIDOR DURING THE LATE AFTERNOON PERIOD...AND THEN
THE COASTAL COUNTIES DURING THE EARLY EVENING. FORECAST CAPE
VALUES OF AROUND 1000 TO 1500 AND FORECAST CAPE PROFILES INDICATE
ISOLATED STRONGER STORMS MAY PRODUCE STRONG GUSTY WINDS AND MAYBE
SMALL HAIL.

A SLIGHT DRIER AND COOLER AIRMASS WILL THEN FILTER ACROSS SE TX...
WITH ONSHORE WINDS RETURNING GULF MOISTURE BY THURSDAY. THE GFS
AND ECMWF BOTH SHOW A SOUTHWESTERLY FLOW OVER SE TX BY THE WEEKEND
AND EARLY NEXT WEEK AS A TROUGH OF LOW PRESSURE DEVELOPS OVER THE
NORTHERN PLAINS INTO THE BAJA CA. THIS PATTERN SHOULD RETURN AT
LEAST ISOLATED RAIN CHANCES TO SE TX OVER THE WEEKEND.

40

MARINE...
A WEAK COLD FRONT WILL CROSS THE WATERS TONIGHT ACCOMPANIED BY
SCATTERED SHOWERS AND THUNDERSTORMS. MODERATE OFFSHORE FLOW IS
EXPECTED BEHIND THE FRONT ON TUESDAY. WITH A HIGH PRESSURE RIDGE
OVERHEAD...WINDS WILL BE LIGHT ON WEDNESDAY. THE HIGH PUSHES EAST
ON THURSDAY WITH WINDS BECOMING BACK ONSHORE ON THURSDAY AND
FRIDAY AS THE HIGH PRESSURE RIDGE PUSHES EAST. 46

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      76  52  72  51  74 /  60  10  10  10  10
HOUSTON (IAH)              78  56  73  52  75 /  60  20  10  10  10
GALVESTON (GLS)            77  62  70  61  71 /  50  30  10  10  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

DISCUSSION...38

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
502 AM CST TUE DEC 4 2012

TXZ163-164-176>179-195>200-210>214-226-227-235>238-051300-
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-
502 AM CST TUE DEC 4 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

PATCHY FOG THAT MAY BE DENSE AT TIMES WILL LIFT BY 9 AM ACROSS
THE COASTAL AND CENTRAL COUNTIES. SHOWERS AND THUNDERSTORMS WILL
THEN BE POSSIBLE...MAINLY THIS AFTERNOON AND EARLY THIS EVENING
AHEAD OF A COLD FRONT. ISOLATED STRONG TO SEVERE THUNDERSTORMS ARE
POSSIBLE DURING THE MID AND LATE AFTERNOON PERIOD. POSSIBLE
HAZARDOUS WEATHER CONDITIONS ARE STRONG GUSTY WINDS AND SMALL
HAIL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED THIS AFTERNOON AND EVENING.