Severe Thunderstorm Warning 151, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1011 PM CST WED DEC 19 2007

.UPDATE...
ANOTHER UPDATE TO RAISE THE POPS TO 80T 90 FOR THE REMAINDER OF
THE NIGHT. LIFT HAS BEEN ON THE INCREASE AND THE CENTRAL AND
NORTHERN CWA HAS HAD A DRAMATIC INCREASE IN THE AREAL COVERAGE AND
INTENSITY OF THE SHOWERS AND A FEW THUNDERSTORMS.
45

&&

.PREV DISCUSSION... /ISSUED 734 PM CST WED DEC 19 2007/

DISCUSSION...
A QUICK UPDATE TO PACKAGE TO LOWER POPS TONIGHT THROUGH 06Z.
EXPECT TO SEE SHOWERS DEVELOP...PRIMARILY NORTH OF UTS AND ALONG
THE COAST. AS THE NEXT SPEED MAX APPROACHES EXPECTING TO SEE MORE
SHRA/TSRA DEVELOP BUT THAT SHOULD BE 09Z-12Z. THE ASSOCIATED
PACIFIC COLD FRONT IS STILL GETTING ORGANIZED OUT BETWEEN ABILENE
AND CHILDRESS. THE ACTION LOOKS TO BE AFTER MIDNIGHT AND PROBABLY
MORE TOWARD MORNING AS THE LIFT GETS BETTER. THIS UNFORTUNATELY
WILL COINCIDE WITH THE COLDER AIR ALOFT ARRIVING BRINGING GREATER
INSTABILITY. STILL LOOK TO HAVE ENOUGH SEVERE THREAT TO CONTINUE
THE SOME MAY BE SEVERE WORDING. ALSO INCREASE CLOUD COVER
OVERNIGHT AND NUDGED UP A FEW TEMPS MAINLY SOUTH OF I-10. AND EAST
OF CXO.

45

PREV DISCUSSION... /ISSUED 546 PM CST WED DEC 19 2007/

AVIATION (00Z TAF)...
ANY SHOWERS HAVE DISSIPATED THIS EVENING AND SUSPECT THAT THE
ATMOSPHERE HAS STABILIZED A LITTLE BIT WITH THE PASSING OF A JET
STREAK. TAF FORECAST WILL HOLD OFF ANY VCTS/TSRA UNTIL AFTER 06Z
WHEN LIFT FROM THE SHORTWAVE TROUGH AND COOLER AIR ALOFT BEGIN
IMPACT SE TX. THE 09Z TO 15Z TIME FRAME SEEMS TO BE WHEN THE
AIRMASS WILL BE MOST UNSTABLE AND WHEN LIFT WILL BE MAXIMIZED. AS
SUCH...WILL SLOWLY BUILD DOWN THUNDERSTORM ACTIVITY FROM KCLL AND
KUTS THROUGH THE HOUSTON METRO TERMINALS IN THE 12Z TIME FRAME
AND CLOSER TO 15Z ALONG THE COAST. TIMING OF THIS WILL LARGELY
DEPEND ON THE FORCING AND INSTABILITY THAT DEVELOPS ACROSS THE
AREA. A FEW OF THESE STORMS COULD BE STRONG/SEVERE BUT WILL WAIT
AND SEE FOR DEVELOPMENT BEFORE REALLY JUMPING ON THAT IN THE
TAFS. AGAIN THE BEST TIME FOR THE SEVERE THREAT SEEMS TO BE AFTER
THE 06Z-09Z TIME FRAME. CLEARING SHOULD OCCUR AFTER 15Z FOR
KCLL/KUTS AND BASICALLY AFTER 18Z FOR EVERYONE ELSE IN SE TX.
WINDS SHOULD INCREASE FROM THE NW BEHIND THE PACIFIC FRONT.

OVERPECK/39

PREV DISCUSSION... /ISSUED 259 PM CST WED DEC 19 2007/

DISCUSSION...
A FAIRLY PROGRESSIVE PATTERN WILL PUSH A FEW SHORTWAVE TROUGHS
ACROSS SE TX OVER THE NEXT SEVEN DAYS. THE MODEL DATA IN THE
SHORT RANGE LOOKED SIMILAR. BEYOND MONDAY...THE GFS LOOKED TO
WANDER A BIT FROM 24 HOURS AGO. FOR NOW WILL STICK WITH THE
PREVIOUS FORECAST IN THE EXTENDED WHICH IS FAIRLY CONSISTENT WITH
THE LATEST ECMWF.

THE MAIN PROBLEM OF THE DAY CONCERNS POPS AND WEATHER FOR TONIGHT
AND EARLY THURSDAY. THE WARM FRONT WAS WELL TO THE NORTH OF SE TX.
WITH GOOD LOW LEVEL MOISTURE AND WARM AIR TRANSPORT FROM THE
SOUTHEAST...THUNDERSTORMS SHOULD RESULT LATER THIS EVENING AS THE
SHORTWAVE TROUGH CURRENTLY MOVING ACROSS WEST TEXAS PUSHES OVER
THIS PART OF THE STATE. THE MODELS INDICATE THAT THE BEST CHANCES
FOR SEVERE WEATHER WILL BE ROUGHLY BETWEEN MIDNIGHT TONIGHT TO
AROUND SUNRISE TOMORROW. THE BEST CHANCES FOR SEVERE ALSO LOOK TO
OCCUR OVER THE NORTHEASTERN COUNTIES...HOWEVER THE SYSTEM DOES NOT
LOOK TO GET ORGANIZED UNTIL IT PUSHES EAST AND NORTHEAST OF THE
FORECAST AREA. LIKELY POPS ARE EXPECTED ALONG AND AHEAD OF THE COLD
FRONT WITH THESE ENDING ALONG THE COAST AROUND MID MORNING. THE
FRONT PUSHES BACK NORTHWARD FRIDAY...BRINGING WITH IT ANOTHER
CHANCE OF RAIN AHEAD OF THE COLD FRONTAL PASSAGE LATE SATURDAY.

THE MODELS DIFFER ON THE POSSIBLE WEATHER FOR EARLY NEXT WEEK. A
SHORTWAVE TROUGH IS FORECAST TO PUSH ACROSS THE SOUTHERN PLAINS.
FOR NOW THE AFFECTS OF THE SYSTEM LOOK TO STAY TO THE NORTH OF SE
TX.

40

AVIATION...
MVFR CIGS SHOULD REDEVELOP THIS EVENING. FOG SHOULD NOT BE TOO BIG
OF A CONCERN AS WINDS SHOULD REMAIN UP. EXPECT INCREASING COVERAGE
OF SHRA/TSTMS LATER THIS EVENING AND DURING THE OVERNIGHT HOURS AS
UPPER DISTURBANCE CURRENTLY OVER NEW MEXICO DRAWS ADDITIONAL GULF
MOISTURE INTO THE REGION AND LARGE SCALE LIFT INCREASES AS IT
MOVES FURTHER EAST. MAY SEE SOME ISOLATED STRONG STORMS AFTER
MIDNIGHT AND TOWARD MORNING PRIMARILY ALONG/EAST OF I-45...BUT IT
CURRENTLY LOOKS LIKE THE BETTER THREAT OF SVR STORMS WILL BE IN E
TX AND LA WHERE EVERYTHING LOOKS TO GET A LITTLE BETTER ORGANIZED.
CANNOT RULE OUT SOME LOCALLY HEAVY RAINFALL EITHER CONSIDERING
AVAILABLE MOISTURE SHOULD BE WELL ABOVE NORMAL FOR THIS TIME OF
YEAR. RAINFALL FROM END FROM NW TO SE AS A WEAK PACIFIC FRONTAL
BOUNDARY MOVES OFF THE COAST DURING MID TO LATE MORNING HOURS
THURS. CLEAR SKIES AND VFR BEHIND THE BOUNDARY. 47

 &&

MARINE...
DEWPOINTS NOT EXPECTED TO GET MUCH ABOVE CURRENT WATER TEMPS
TONIGHT SO DO NOT ANTICIPATE MUCH IN THE WAY OF SEA FOG.
OTHERWISE...WINDS AND SEAS WILL INCREASE TONIGHT AHEAD OF AN
UPPER LEVEL TROUGH MOVES ACROSS N TX. WILL GO AHEAD AND HOIST TO
CAUTION FLAGS IN THE 20-60NM GROUP LATER TONIGHT. SPEAKING OF THE
20-60NM GROUP...UNLESS THERE IS SOME SORT OF SMALL BOUNDARY WE ARE
NOT SEEING OUT THERE...WILL BE WATCHING 42019 DURING THE NEXT
COUPLE HOURS AS IT APPEARS THE WIND DIRECTION MAY BE STUCK IN A NE
DIRECTION VERSUS SE WHICH SURROUNDING OBS SHOW. NDBC MAY NEED TO
TURN THIS SENSOR OFF IF THATS THE CASE. WEAK PACIFIC FRONTAL
BOUNDARY SHOULD BE PUSHING OFF THE COAST IN THE MID AND LATE
MORNING HOURS THURS BRINGING AN END TO RAIN CHANCES. ONSHORE FLOW
RESUMES FRI AND INCREASES AHEAD OF THE NEXT (STRONGER) FRONT
SOMETIME SATURDAY - STILL SOME UNCERTAINTY REGARDING TIMING OF
THIS ONE. 47

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      58  73  45  75  59 /  90  20  10  10  40
HOUSTON (IAH)              63  76  48  77  59 /  90  60  10  10  20
GALVESTON (GLS)            66  74  59  71  65 /  90  70  10  10  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 9 AM CST THURSDAY FOR
     THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA
     SHIP CHANNEL 20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO
     FREEPORT 20 TO 60 NM.

&&

DISCUSSION...45

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
839 AM CST WED DEC 19 2007

TXZ163-164-176>179-195>200-210>214-226-227-235>238-201445-
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-
839 AM CST WED DEC 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

...SLIGHT RISK FOR SEVERE THUNDERSTORMS OVERNIGHT TONIGHT...

.DAY ONE...TODAY AND TONIGHT

INCREASING MOISTURE LEVELS AND INSTABILITY IN COMBINATION WITH A
FAST MOVING UPPER LEVEL DISTURBANCE WILL RESULT IN THE DEVELOPMENT
OF THUNDERSTORMS OVER THE REGION TONIGHT ESPECIALLY OVER THE
NORTHERN PORTIONS. SOME OF THE STORMS MAY BECOME SEVERE MAINLY
FROM MIDNIGHT TO AROUND SUNRISE. THE MAIN THREAT WILL BE HAIL.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

AN APPROACHING UPPER LEVEL DISTURBANCE AND A STRONG COLD FRONT
WILL MOVE ACROSS THE REGION ON SATURDAY. EXPECT SCATTERED
SHOWERS AND THUNDERSTORMS WITH THIS FRONT. THE FRONT IS EXPECTED
TO MOVE OFFSHORE BY SATURDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED TONIGHT AND EARLY THURSDAY
MORNING.