Tornado Warning 10, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1220 PM CDT FRI APR 17 2009

.AVIATION...
SHOWER AND THUNDERSTORM ACTIVITY HAS PICKED UP SOUTH AND EAST OF
HIGHWAY 59.  COASTAL AND HOUSTON METRO TAFS ARE TOGGLING BETWEEN
VFR/MVFR CIG AND VSBY AS THUNDERSTORMS MOVE THROUGH THE AREA.  WITH
ABUNDANT LOW LEVEL MOISTURE AND A DIFLUENT WIND PATTERN
ALOFT...WOULD EXPECT GENERAL TSRA ACTIVITY TO CONTINUE OVER NIGHT.

A NEW ROUND OF CONVECTIVE ACTIVITY IS LIKELY ON SATURDAY MORNING
WHEN AN UPPER LEVEL SHORTWAVE TROF SWINGS AROUND THE SOUTHERN
PERIPHERY OF THE UPPER LEVEL LOW PRESSURE SYSTEM THAT CENTERED OVER
THE MID-WEST. IT SHOULD BEGIN TO AFFECT THE WESTERN TAF SITES
BETWEEN 14-18Z AND THE REMAINDER OF THE FORECAST AREA BETWEEN
18-00Z. ANTICIPATE WIDESPREAD MVFR/IFR SHRA/TSRA CONDITIONS TO COVER
MUCH OF THE AREA BY SATURDAY AFTERNOON. 44

&&

.PREV DISCUSSION.../1020 PM CDT FRI APR 17 2009/
NOT SEEING A WHOLE LOT OF DEVELOPMENT OUT WEST THIS EVENING. THIS
TIME LAST NIGHT THE START OF THE MCS WAS WELL UNDERWAY OUT THERE.
AT ANY RATE THE BULK OF TODAYS ACTIVITY CONTINUING TO MOVE OFF TO
THE EAST BUT STREAMER SHRA ARE BECOMING MORE PROMINENT ALONG/OVER
A N/S LINE THRU THE MIDDLE OF THE FA. THIS SET UP OF THE MOISTURE
AXIS SHOULD GIVE THE WRN PORTIONS OF THE CWA (ESP COLORADO/AUSTIN
COUNTIES) A BREAK FROM THE PCPN. HOWEVER IT IS NOT LIKELY THAT WE
ARE OUT OF THE WOODS JUST YET AS THE MAIN UPPER LOW IS CONTINUING
TO SPIN OVER SRN CO/NRN NM TONIGHT. AND GIVEN THE QUICK RETURN OF
PCPN IN THE WAKE OF THE MCS...THE ATMS DOES SEEM TO HAVE RECOVER-
ED NICELY. GOOD CHC/LIKELY POPS TO HOLD UFN. 41

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      64  76  60  80  52 /  60  60  40   0   0
HOUSTON (IAH)              67  78  62  82  54 /  60  60  60  10   0
GALVESTON (GLS)            69  76  66  80  61 /  50  60  60  10   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLOOD WATCH THROUGH SATURDAY EVENING FOR THE FOLLOWING ZONES:
     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.

GM...SMALL CRAFT ADVISORY UNTIL 11 AM CDT SATURDAY FOR THE FOLLOWING
     ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
     20 NM TO 60 NM...WATERS FROM FREEPORT TO THE MATAGORDA SHIP
     CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20
     TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
505 AM CDT FRI APR 17 2009

GMZ330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-
227-235>238-181200-
AUSTIN-BRAZORIA-BRAZOS-BURLESON-CHAMBERS-COLORADO-FORT BEND-
GALVESTON-GALVESTON BAY-GRIMES-HARRIS-HOUSTON-JACKSON-LIBERTY-
MADISON-MATAGORDA-MATAGORDA BAY-MONTGOMERY-POLK-SAN JACINTO-
TRINITY-WALKER-WALLER-WASHINGTON-
WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM-
WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM-
WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM-
WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM-WHARTON-
505 AM CDT FRI APR 17 2009

...SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST TEXAS
THROUGH SATURDAY EVENING...

...LOCALLY HEAVY RAINFALL POSSIBLE THROUGH SATURDAY EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

AN APPROACHING UPPER LEVEL DISTURBANCE AND INCREASING MOISTURE
LEVELS WILL RESULT IN THE DEVELOPMENT OF NUMEROUS SHOWERS AND
THUNDERSTORMS OVER SOUTHEAST TEXAS MAINLY THIS AFTERNOON AND
TONIGHT.

THE COMBINATION OF A HIGHLY UNSTABLE AIRMASS AND SIGNIFICANT SHEAR
IN THE LOW LEVELS WILL RESULT IN THE POSSIBILITY OF A FEW STORMS
BECOMING SEVERE. THE PRIMARY SEVERE WEATHER THREATS WILL BE LARGE
HAIL DAMAGING WINDS...WITH ISOLATED TORNADOES ALSO POSSIBLE. THE
PRIMARY THREAT AREA FOR SEVERE WEATHER WILL BE WEST OF THE
INTERSTATE 45 CORRIDOR.

IN ADDITION...LOCALLY HEAVY DOWNPOURS WILL BE POSSIBLE. MINOR
FLOODING OF STREETS...FEEDER ROADS...SECONDARY ROADS...AND LOW
WATER CROSSINGS WILL BE POSSIBLE WHERE TRAINING OF STORMS OCCURS.
HOWEVER...RECENT DRY CONDITIONS ARE EXPECTED TO MITIGATE THE
OVERALL FLOODING THREAT. RAINFALL TOTALS THROUGH EARLY SATURDAY
ARE EXPECTED TO AVERAGE 1 TO 2 INCHES...WITH ISOLATED TOTALS OF 3
TO 6 INCHES POSSIBLE.

STRONG EASTERLY WINDS WILL RESULT IN ELEVATED TIDE LEVELS ALONG
THE UPPER TEXAS COAST AND SHORES OF THE BAYS. TIDE LEVELS WILL RUN
1 TO 2 FEET ABOVE NORMAL.

.DAY TWO...SATURDAY THROUGH SATURDAY NIGHT

A SLOW MOVING UPPER LEVEL LOW PRESSURE SYSTEM WILL COMBINE WITH A
MOIST AND UNSTABLE AIRMASS TO RESULT IN ADDITIONAL SHOWERS AND
THUNDERSTORMS THROUGH SATURDAY EVENING.

THE COMBINATION OF A HIGHLY UNSTABLE AIRMASS AND SIGNIFICANT SHEAR
IN THE LOW LEVELS WILL RESULT IN THE POSSIBILITY OF A FEW STORMS
BECOMING SEVERE. THE PRIMARY SEVERE WEATHER THREATS WILL BE LARGE
HAIL DAMAGING WINDS...WITH ISOLATED TORNADOES ALSO POSSIBLE.

IN ADDITION...LOCALLY HEAVY RAINFALL WILL BE AGAIN POSSIBLE. STORM
TOTAL RAINFALL AMOUNTS THROUGH EARLY SUNDAY ARE EXPECTED TO RANGE
FROM 2 TO 4 INCHES NORTH OF THE INTERSTATE 10 CORRIDOR TO 1 TO 3
INCHES SOUTH OF INTERSTATE 10. LOCALIZED RAINFALL TOTALS OF 4 TO 7
INCHES WILL BE POSSIBLE. FLOODING PROBLEMS WILL BE POSSIBLE WHERE
TRAINING OF STORMS OCCURS.

A COLD FRONT WILL CROSS THE AREA LATE SATURDAY NIGHT ENDING THE
RAIN CHANCES AS THE THUNDERSTORM ACTIVITY SHIFTS INTO THE GULF OF
MEXICO.

.DAYS THREE THROUGH SEVEN...SUNDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AT ANY TIME THROUGH SATURDAY EVENING.