Flash Flood Warning 4, NWS Houston/Galveston, TX

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

.DISCUSSION...
SHOWERS AND THUNDERSTORMS FROM A LARGE AND SLOW MOVING MCS HAVE PRODUCED
A LOT OF HEAVY RAINFALL AND SOME SEVERE WEATHER ACROSS PORTIONS OF SOUTHEAST
TEXAS TODAY (SEE THE LATEST LSRHGX). SOME RAINFALL REPORTS BEING RECEIVED
ARE ACTUALLY QUITE CLOSE TO THE KHGX 88D ESTIMATED 8 TO 10 INCH BULLSEYES
BETWEEN BELLVILLE AND SCHULENBURG. BASED ON THE HEAVY RAINFALL THAT HAS
ALREADY OCCURRED AND THE POTENTIAL FOR ADDITIONAL HEAVY RAINS THIS AFTERNOON
THROUGH SATURDAY EVENING...HAVE EXTENDED THIS MORNINGS FLOOD WATCH
THROUGH 9 PM ON SATURDAY AND HAVE NOW INCLUDED ALL OF SOUTHEAST TEXAS.
VERY HIGH MOISTURE LEVELS WITH PRECIPITABLE WATER VALUES IN A 1.75 TO
2.00 INCH RANGE...GOOD SURFACE CONVERGENCE AND A VERY DIFFLUENT FLOW
ALOFT SUPPORT ADDITIONAL SHOWER AND THUNDERSTORM DEVELOPMENT BETWEEN
TONIGHT AND TOMORROW NIGHT. THINK THE MAIN HEAVY RAIN THREAT WILL BE
ALONG AND NORTH OF THE HIGHWAY 59 CORRIDOR. OUR HWO ISSUED THIS AFTERNOON
IS CALLING FOR ADDITIONAL RAINFALL TOTALS TO AVERAGE 2 TO 4 INCHES...AND
THIS COULD EASILY BOOST TWO DAY TOTALS (FRIDAY AND SATURDAY) UP TO 15
TO 20 INCHES BETWEEN THE BELLVILLE AND SCHULENBURG AREAS. IN ADDITION
TO THE HEAVY RAIN THREAT...THERE IS A SLIGHT CHANCE OF SEVERE THUNDERSTORMS
THROUGH SATURDAY EVENING AS DISTURBANCES CONTINUE TO ROTATE AROUND
THE STRONG UPPER LEVEL LOW. A COLD FRONT WILL CROSS THE AREA LATE SATURDAY
NIGHT AND WILL DRY THINGS OUT. EXPECT COOL NIGHTS AND MILD DAYS SUNDAY
THROUGH THE MIDDLE OF NEXT WEEK WITH A DRY AIRMASS IN PLACE. A GRADUAL
WARMUP CAN BE EXPECTED DURING THE SECOND HALF OF NEXT WEEK AS A RETURN
FLOW OFF THE GULF BECOMES ESTABLISHED. AS OF NOW...ALL OF NEXT WEEK
LOOKS DRY.  42
&&

.AVIATION...
ON GOING TRENDS OF THE MCS OVER THE BRAZOS VALLEY INDICATE SLOW
MOVEMENT INTO THE I-45 CORRIDOR. WILL SEE PREVAILING VCTS/TSRA
THROUGH THE EVENING HOURS PERHAPS LONGER DEPENDING ON HOW MUCH
INSTABILITY THE STORMS CAN TAP. INSTABILITY IS LIMITED ACROSS
AREAS NORTH OF I-10 BUT THIS UNSTABLE AIR COULD MOVE FURTHER
NORTH THIS AFTERNOON WITH STRONG LLJ PRESENT. WILL LIKELY SEE
+TSRA BUT WILL HOLD OFF ON MENTIONING HAIL/GR FOR NOW DUE TO
LIMITED INSTABILITY AT THE MOMENT. OVERNIGHT SHOULD SEE A LULL IN
ACTIVITY AND THEN SATURDAY SHOULD HAVE ANOTHER ROUND OF TSRA IN
THE LATE MORNING. POSSIBLE TO GET ANOTHER SQUALL LINE DEVELOPING
C TX OVERNIGHT WHICH WILL MOVE INTO THE AREA MUCH LIKE TODAY.
EXTENDED PART OF THE TAF TRIES TO INDICATE A HIGH POSSIBILITY OF
A SECOND ROUND OF STORMS. WINDS WILL LIKELY VEER FROM ESE TO MORE
SSE OVER THE NEXT 24 HRS.

39

&&

.MARINE...
ONSHORE WINDS SHOULD CONTINUE OVERNIGHT AND WILL KEEP SCA GOING FOR
OFFSHORE WATERS THROUGH SAT MORNING.  WINDS OVER THE BAYS MAY REMAIN
QUITE GUSTY AND WILL KEEP SCA GOING THROUGH 10PM TONIGHT.  SCA MAY
BE NEED TO BE EXTENDED INTO SAT AFTERNOON.  COLD FRONT WILL PUSH OFF
THE COAST SUNDAY AS THE LOW PRESSURE SYSTEM PULLS INTO THE MIDWEST.
ANOTHER SCA MAY BE NEEDED POST FRONTAL FOR SUN NIGHT INTO MON.  HIGH
PRESSURE SHOULD BUILD OVER SE TX MON NIGHT INTO TUE ALLOWING FOR
WINDS AND SEAS TO SUBSIDE.  RETURN FLOW MAY RAMP UP AGAIN ON WED BUT
SHOULD LIMIT WIND SPEEDS AND SEAS TO MODERATE LEVELS.

39

&&

.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 10 PM CDT THIS EVENING FOR THE
     FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY.

     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.

&&

DISCUSSION...42
AVIATION/MARINE...39

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
212 PM 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-
212 PM CDT FRI APR 17 2009

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

...FLOOD WATCH IN EFFECT FOR ALL OF SOUTHEAST TEXAS THROUGH
SATURDAY EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

DISTURBANCES ROTATING AROUND A STRONG STORM SYSTEM WILL CONTINUE TO
SUPPORT THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS PORTIONS
OF SOUTHEAST TEXAS. SOME OF THE STRONGER STORMS MAY BECOME SEVERE
AND COULD PRODUCE STRONG DAMAGING WINDS...LARGE HAIL AND ISOLATED
TORNADOES. IN ADDITION TO THE SEVERE WEATHER THREAT...VERY HIGH MOISTURE
LEVELS WILL PERSIST ACROSS MUCH OF THE AREA AND WILL SUPPORT THE THREAT
FOR LOCALLY HEAVY RAINFALL. FLOODING OF STREETS...FEEDER ROADS...SECONDARY
ROADS...LOW WATER CROSSINGS...AND AREA CREEKS AND RIVERS WILL BE POSSIBLE
WHERE TRAINING OF STORMS OCCURS.

.DAY TWO...SATURDAY THROUGH SATURDAY NIGHT

DISTURBANCES ROTATING AROUND A STRONG STORM SYSTEM WILL CONTINUE TO
SUPPORT THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS ACROSS PORTIONS
OF SOUTHEAST TEXAS. SOME OF THE STRONGER STORMS MAY BECOME SEVERE
AND COULD PRODUCE STRONG DAMAGING WINDS...LARGE HAIL AND ISOLATED
TORNADOES. IN ADDITION TO THE SEVERE WEATHER THREAT...VERY HIGH MOISTURE
LEVELS WILL PERSIST ACROSS MUCH OF THE AREA AND WILL SUPPORT THE THREAT
FOR LOCALLY HEAVY RAINFALL. FLOODING OF STREETS...FEEDER ROADS...SECONDARY
ROADS...LOW WATER CROSSINGS...AND AREA CREEKS AND RIVERS WILL BE POSSIBLE
WHERE TRAINING OF STORMS OCCURS.

RAINFALL TOTALS FOR TODAY AND SATURDAY ARE EXPECTED TO AVERAGE 2 TO
4 INCHES. WHERE HEAVY RAINFALL HAS ALREADY OCCURRED...ISOLATED TWO
DAY TOTALS OF 15 TO 20 INCHES ARE POSSIBLE...ESPECIALLY ACROSS PORTIONS
OF NORTHWEST COLORADO COUNTY AND NORTHERN AUSTIN COUNTY. THE THREAT
FOR THE HEAVIEST RAINFALL IS EXPECTED GENERALLY ALONG AND NORTH OF THE
U.S. HIGHWAY 59 CORRIDOR...GENERALLY ALONG AND NORTH OF A LINE FROM
EDNA TO RICHMOND TO HOUSTON TO CLEVELAND TO CORRIGAN.

A COLD FRONT WILL CROSS THE AREA LATE SATURDAY NIGHT ENDING THE RAIN
CHANCES AND SEVERE WEATHER THREAT ACTIVITY SHIFTS TO THE EAST OF THE
AREA.

.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.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
102 PM CDT FRI APR 17 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1047 AM     HAIL             WEIMAR                  29.70N 96.78W
04/17/2009  M0.50 INCH       COLORADO           TX   EMERGENCY MNGR

            MARBLE SIZED HAIL REPORTED IN WEIMAR.

1248 PM     HEAVY RAIN       WEIMAR                  29.70N 96.78W
04/17/2009  M5.00 INCH       COLORADO           TX   COUNTY OFFICIAL

            TWO ROADS CLOSED INCLUDING FM 155...JUST SOUTH OF WEIMAR.

&&

DHELVY

PRELIMINARY LOCAL STORM REPORT...CORRECTED
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
237 PM CDT FRI APR 17 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1047 AM     HAIL             WEIMAR                  29.70N 96.78W
04/17/2009  M0.75 INCH       COLORADO           TX   EMERGENCY MNGR

            PENNY SIZED HAIL REPORTED IN WEIMAR.

1225 PM     TSTM WND DMG     BRENHAM                 30.16N 96.40W
04/17/2009                   WASHINGTON         TX   LAW ENFORCEMENT

            HARTZ CHICKEN RESTAURANT ROOF BLOWN OFF...RESIDENTIAL
            HOME WINDOWS BLOWN OUT. TREES AND POWER LINES DOWN AROUND
            COUNTY.

1248 PM     HEAVY RAIN       WEIMAR                  29.70N 96.78W
04/17/2009  M5.00 INCH       COLORADO           TX   COUNTY OFFICIAL

            TWO ROADS CLOSED INCLUDING FM 155...JUST SOUTH OF WEIMAR.

0200 PM     HEAVY RAIN       FRELSBURG               29.87N 96.55W
04/17/2009  M10.00 INCH      COLORADO           TX   LAW ENFORCEMENT

            10 INCHES OF RAIN IN NORTHERN COLORADO COUNTY.

0200 PM     HEAVY RAIN       WEIMAR                  29.70N 96.78W
04/17/2009  M8.00 INCH       COLORADO           TX   LAW ENFORCEMENT

0200 PM     HEAVY RAIN       COLUMBUS                29.70N 96.55W
04/17/2009  M4.00 INCH       COLORADO           TX   LAW ENFORCEMENT

&&

DHELVY