Alert archive / Texas / Flash Flood Watches in 2015

Flash Flood Watch 4, NWS Houston/Galveston, TX

May 11, 201523 counties in Texas

NWS Houston/Galveston, TX issued this flash flood watch at May 11, 2015, 10:52 AM CDT for 23 counties in Texas. It was in force for 24 hr.

The area

The counties it named.

The facts

Issued: May 11, 2015, 10:52 AM CDT (15:52 UTC)
Expired: May 12, 2015, 10:35 AM CDT
In force: 24 hr
Issued by: NWS Houston/Galveston, TX
Flood severity: None

All 23 counties

Austin County, TX, Brazoria County, TX, Brazos County, TX, Burleson County, TX, Chambers County, TX, Colorado County, TX, Fort Bend County, TX, Galveston County, TX, Grimes County, TX, Harris County, TX, Houston County, TX, Jackson County, TX, Liberty County, TX, Madison County, TX, Matagorda County, TX, Montgomery County, TX, Polk County, TX, San Jacinto County, TX, Trinity County, TX, Walker County, TX, Waller County, TX, Washington County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 91 km from the middle of the area, began a volume at 15:55 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 3.9 hours before the alert went out and 242 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 1889 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 597 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 75 m²/s²
0-3 km storm-relative helicity: 152 m²/s²
Significant tornado parameter: 0.6
Supercell composite: 4.4

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Houston/Galveston, TX wrote its last area forecast discussion before this flash flood watch went out at May 11, 8:42 AM CDT, 2 hours 10 minutes earlier.

Area forecast discussion, May 11, 8:42 AM CDT, 2 hours 10 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
842 AM CDT MON MAY 11 2015

.UPDATE...
MORNING FORECAST UPDATE.

&&

.DISCUSSION...
LINE OF THUNDERSTORMS CURRENTLY RUNS WEST TO EAST ALONG A
BRENHAM...CONROE...CLEVELAND LINE. STORMS CONTINUE TO WEAKEN BUT
STILL CAPABLE OF HEAVY RAINFALL. SEVERE THREAT LOOKS TO BE
DIMINISHED WITH OUTFLOW FROM THE STORMS OUT RUNNING UPDRAFTS.
ELEVATED STORMS MAY BRIEFLY PULSE UP IN INTENSITY AND PRODUCE 2
INCHES OF RAIN IN AN HOUR. SFC OBS ALSO SHOW WEAK FRONTAL BOUNDARY
JUST TO THE NORTH OF THE AREA. WILL NEED TO WATCH FOR ADDITIONAL
DEVELOPMENT THIS AFTERNOON AS CURRENT STORMS DISSIPATE AND AIRMASS
RECOVERS. AIRMASS MAY STILL BE MOIST/UNSTABLE SOUTH OF OUTFLOW
WHICH COULD BE A FOCUS FOR THUNDERSTORM DEVELOPMENT THIS
AFTERNOON. MAIN CHANGES TO THE FORECAST WAS TO INCREASE RAIN
CHANCES WHERE STORMS ARE ONGOING AND TO ACCOUNT FOR FUTURE TRENDS.

39

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      79  66  77  67  80 / 100  80  70  60  60
HOUSTON (IAH)              82  71  81  69  82 /  90  70  70  40  40
GALVESTON (GLS)            79  75  81  74  79 /  50  60  60  30  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 11 AM CDT THIS MORNING
     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...39

Hazardous weather outlook, May 11, 6:56 AM CDT, 3 hours 56 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
656 AM CDT MON MAY 11 2015

TXZ163-164-176>179-195>200-210>213-226-227-121200-
AUSTIN-BRAZOS-BURLESON-COLORADO-FORT BEND-GRIMES-HARRIS-HOUSTON-
LIBERTY-MADISON-MONTGOMERY-POLK-SAN JACINTO-TRINITY-WALKER-WALLER-
WASHINGTON-WHARTON-
656 AM CDT MON MAY 11 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

A LINE OF CLUSTERED THUNDERSTORMS WILL TRAIN ACROSS THE CENTRAL
FORECAST AREA TODAY...THIS LINE WILL SLOWLY SAG SOUTHWARD THROUGH
THE AFTERNOON. THE MAIN THREAT WILL BE HEAVY RAIN LEADING TO
FLOODING ISSUES. THERE IS A POTENTIAL FOR AN ISOLATED SEVERE STORM
WITHIN THIS CLUSTERED LINE THAT COULD PRODUCE DAMAGING WIND GUSTS
AND HAIL TO THE SIZE OF QUARTERS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A SERIES OF HARD-TO-TIME DISTURBANCES WILL MOVE OVERHEAD...WITH
STRONG TO SEVERE THUNDERSTORMS POSSIBLE AGAIN ACROSS THE REGION
MONDAY EVENING THROUGH EARLY TUESDAY. ANOTHER ROUND OF STRONG TO
SEVERE THUNDERSTORMS COULD AFFECT THE REGION LATE TUESDAY INTO
EARLY WEDNESDAY.

LOCALIZED HEAVY RAINFALL AND FLOODING WILL BE POSSIBLE THROUGH THE
WEEK. SOME LOCATIONS COULD SEE SOME SIGNIFICANT RAINFALL ACCUMULATIONS
BY THURSDAY. HOWEVER...THERE IS CONSIDERABLE UNCERTAINTY REGARDING
THE TIMING AND LOCATION OF THE MOST ACTIVE WEATHER. THIS SITUATION
WILL BE CLOSELY MONITORED.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED PERIODICALLY THROUGH MID WEEK.

TXZ214-235>238-121200-
BRAZORIA-CHAMBERS-GALVESTON-JACKSON-MATAGORDA-
656 AM CDT MON MAY 11 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

ALTHOUGH THE THREAT IS DIMINISHING DUE TO WEAKENING ONSHORE
WINDS...SLIGHTLY HIGHER THAN NORMAL SURF AND RIP CURRENTS WILL
PERSIST ALONG LOCAL AREA BEACHES. SWIM NEAR A LIFEGUARD.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

RAIN CHANCES WILL FURTHER INCREASE SUNDAY NIGHT THROUGH NEXT WEEK
AS MOISTURE LEVELS INCREASE AND A SERIES OF HARD-TO-TIME DISTURBANCES
MOVE OVERHEAD...WITH STRONG TO SEVERE THUNDERSTORMS POSSIBLE ACROSS
THE REGION LATE MONDAY INTO EARLY TUESDAY. LOCALIZED HEAVY RAINFALL
AND FLOODING WILL ALSO BE POSSIBLE THROUGH THE WEEK. SOME LOCATIONS
COULD SEE SOME SIGNIFICANT RAINFALL ACCUMULATIONS BY THE END OF
NEXT WEEK. HOWEVER...THERE IS CONSIDERABLE UNCERTAINTY REGARDING
THE TIMING AND LOCATION OF THE MOST ACTIVE WEATHER. THIS SITUATION
WILL BE CLOSELY MONITORED.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED DURING THE WORK WEEK.

In the hours before

Local storm report, May 11, 8:14 AM CDT, 2 hours 38 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
814 AM CDT MON MAY 11 2015

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

0811 AM     FLASH FLOOD      3 SSE HUNTSVILLE        30.67N  95.53W
05/11/2015                   WALKER             TX   LAW ENFORCEMENT

            ROADS NOT PASSABLE IN ELKINS LAKE SUBDIVISION

&&

EVENT NUMBER HGX1500196

41

Local storm report, May 11, 8:40 AM CDT, 2 hours 12 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
840 AM CDT MON MAY 11 2015

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

0356 AM     TSTM WND DMG     2 NE GRAPELAND          31.51N  95.46W
05/11/2015                   HOUSTON            TX   EMERGENCY MNGR

            THUNDERSTORM WINDS DOWNED TREES AND THREE CONCRETE
            UTILITY POLES... AND TOOK THE ROOF OFF OF A TRACTOR
            SHED.

&&

EVENT NUMBER HGX1500197

42

Local storm report, May 11, 9:19 AM CDT, 1 hour 33 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
919 AM CDT MON MAY 11 2015

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

0910 AM     HEAVY RAIN       7 E HUNTSVILLE          30.71N  95.44W
05/11/2015  M4.80 INCH       WALKER             TX   PUBLIC

            4.80 INCHES OF RAIN MEASURED AT HWY 190 AND FM 2296

&&

EVENT NUMBER HGX1500198

DO

Local storm report, May 11, 9:25 AM CDT, 1 hour 27 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
925 AM CDT MON MAY 11 2015

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

0900 AM     FLASH FLOOD      HUNTSVILLE              30.71N  95.55W
05/11/2015                   WALKER             TX   EMERGENCY MNGR

            MUTILPLE ROADS CLOSED IN AND AROUND HUNSTVILLE
            INCLUDING 10 COUNTY ROADS.

&&

EVENT NUMBER HGX1500199

DR

Local storm report, May 11, 9:39 AM CDT, 1 hour 13 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
939 AM CDT MON MAY 11 2015

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

0932 AM     FLASH FLOOD      2 SE NAVASOTA           30.38N  96.07W
05/11/2015                   GRIMES             TX   BROADCAST MEDIA

            WATER ACROSS CR 105 NEAR HIGHWAY 6. ON OFF RAMP TO
            HIGHWAY 6 CLOSED DUE TO FLOODING.

&&

EVENT NUMBER HGX1500201

42

Local storm report, May 11, 10:39 AM CDT, 13 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1039 AM CDT MON MAY 11 2015

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

0930 AM     FLASH FLOOD      10 N GROVETON           31.20N  95.16W
05/11/2015                   TRINITY            TX   DEPT OF HIGHWAYS

            COUNTY ROADS 1280... 3154 358 UNDER WATER. FLOODING
            STILL ONGOING.

&&

EVENT NUMBER HGX1500202

DR

The office that day

Everything else NWS Houston/Galveston, TX issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 10, 11:54 PM CDT	Special Weather Statement	HGX	Houston	21 min
May 11, 1:56 AM CDT	Special Weather Statement	HGX	Houston	34 min
May 11, 2:24 AM CDT	Special Weather Statement	HGX	Burleson	36 min
May 11, 2:53 AM CDT	Special Weather Statement	HGX	Madison	52 min
May 11, 3:39 AM CDT	Special Weather Statement	HGX	Trinity	51 min
May 11, 3:42 AM CDT	Special Weather Statement	HGX	Trinity	48 min
May 11, 3:46 AM CDT	Special Weather Statement	HGX	Houston	44 min
May 11, 4:08 AM CDT	Special Weather Statement	HGX	Madison	37 min
May 11, 4:38 AM CDT	Special Weather Statement	HGX	Trinity	52 min
May 11, 4:43 AM CDT	Severe Thunderstorm Warning	HGX	Trinity	32 min
May 11, 5:02 AM CDT	Special Weather Statement	HGX	Walker	43 min
May 11, 5:57 AM CDT	Areal Flood Advisory	HGX	Polk, San Jacinto, Trinity, Walker	3 hr
May 11, 5:59 AM CDT	Special Weather Statement	HGX	Polk	46 min
May 11, 6:28 AM CDT	Severe Thunderstorm Warning	HGX	Polk	32 min
May 11, 6:34 AM CDT	Severe Thunderstorm Warning	HGX	Grimes, Montgomery, Walker	26 min
May 11, 6:43 AM CDT	Areal Flood Advisory	HGX	Brazos, Burleson, Grimes, Montgomery, San Jacinto, Trinity and 2 more	3 hr
May 11, 7:22 AM CDT	Special Weather Statement	HGX	Polk	38 min
May 11, 7:31 AM CDT	Special Weather Statement	HGX	Montgomery	44 min
May 11, 7:41 AM CDT	Tornado Warning	HGX	Montgomery	18 min
May 11, 8:06 AM CDT	Flash Flood Warning	HGX	Grimes, Montgomery, Polk, San Jacinto, Trinity, Walker and 1 more	114 min
May 11, 9:34 AM CDT	Areal Flood Advisory	HGX	Washington	3 hr
May 11, 9:59 AM CDT	Flash Flood Warning	HGX	Austin, Brazos, Burleson, Grimes, Montgomery, Waller and 1 more	2 hr
May 11, 10:03 AM CDT	Flash Flood Warning	HGX	Polk, San Jacinto, Trinity, Walker	117 min
May 11, 11:06 AM CDT	Special Weather Statement	HGX	Montgomery	24 min
May 11, 12:43 PM CDT	Areal Flood Advisory	HGX	Harris	2 hr
May 11, 1:41 PM CDT	Severe Thunderstorm Warning	HGX	Colorado	49 min
May 11, 1:52 PM CDT	Areal Flood Advisory	HGX	Colorado	113 min
May 11, 2:24 PM CDT	Flash Flood Warning	HGX	Colorado	81 min
May 11, 3:03 PM CDT	River Flood Warning	HGX	Burleson, Lee	65 hr

Nearby

Flash Flood Watches in Texas, 2015 Every flash flood watch in 2015

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.