Flash Flood Warning 30, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1129 PM CDT MON MAY 11 2015

.DISCUSSION...
SEE 06Z AVIATION DISCUSSION.

SEE UPDATED MARINE SECTION.

&&

.AVIATION...
PERIODS OF LIGHT TO MODERATE RAIN WILL PERSIST OVER THE SOUTHERN
HALF OF THE FORECAST AREA. GFS/RAP SEEMS TO BE HANDLING THE
SITUATION BEST AND LEANED TOWARD THOSE SOLNS. RAIN SHOULD TAKE A
BRIEF BREAK BUT SCATTERED SHRA/TSRA POSSIBLE AGAIN ON TUESDAY.
VERY LITTLE CONFIDENCE ON WHEN/WHERE EXACTLY SO WILL CARRY VCTS
FOR THE FIRST HALF OF THE DAY. EAST WINDS WILL GRADUALLY BECOME SE
DURING THE AFTN OR EVENING. MVFR CIGS EXPECTED DURING THE MORNING
WILL SCATTER OUT TO VFR CIGS IN THE AFTN. WINDS WILL REMAIN STRONG
TONIGHT ALONG THE COAST DIMINISHING TOWARD MORNING. 43

&&

.MARINE...
WILL EXTEND THE SMALL CRAFT ADVISORY FOR THE GULF WATERS THROUGH
10Z. WINDS SHOULD BEGIN TO DIMINISH IN THE NEXT COUPLE OF
HOURS BUT GENERALLY REMAIN E-SE. THE RAP/GFS/NAM KEEP AND EAST
WIND OF AROUND 15 KNOTS ON TUESDAY SO AM GETTING INCREASINGLY
CONCERNED WITH TIDE LEVELS. TIDES AT NORTH JETTY ARE 2.5 FT AND
RISING WITH A STIFF EAST WIND. NEW MARINE ZONES OUT SHORTLY. 43

&&

.PREV DISCUSSION... /ISSUED 956 PM CDT MON MAY 11 2015/

UPDATE...
SHOWERS AND THUNDERSTORMS CONTINUE THIS EVENING IN THE VICINITY
OF AN OUTFLOW BOUNDARY THAT HAS PUSHED NEAR THE SOUTHERN EXTEND OF
OUR COASTAL WATERS. MESSY 00Z SURFACE ANALYSIS SHOWS A COLD FRONT
DRAPED ALONG THE NORTHERN FRINGES OF THE REGION /ROUGHLY ALONG A
CALDWELL TO GRAPELAND LINE/... WITH AN INCREASING SURFACE PRESSURE
GRADIENT LEADING TO ELEVATED WINDS OVER THE COASTAL WATERS. WATER
VAPOR IMAGERY SHOWS AN APPROACHING DISTURBANCE MOVING NORTHEAST INTO
SOUTH TEXAS FROM MEXICO... AND AS THIS FEATURE NEARS THE REGION
OVERNIGHT ANTICIPATE SHOWER AND THUNDERSTORM ACTIVITY TO INCREASE
FROM THE WEST. WITH WEAK FLOW ALOFT ENCOURAGING SLOW STORM MOTIONS
AND 00Z SOUNDINGS SHOWING PRECIPITABLE WATER VALUES OVER 1.8
INCHES /1.84 AT LAKE CHARLES AND 2.15 AT CORPUS CHRISTI... VALUES
MORE THAN 2 STANDARD DEVIATIONS ABOVE NORMAL/... HEAVY RAIN
CONTINUES TO BE THE MAIN THREAT WITH ANY SHOWER OR THUNDERSTORM
THAT DEVELOPS.

WHERE THESE BOUNDARIES LAY WHEN THE SHORTWAVE REACHES THE AREA
WILL PLAY A BIG ROLE IN WHICH AREAS HAVE THE HIGHEST THREAT FOR
POTENTIAL FLOODING. HI-RES GUIDANCE HIGHLIGHTS THE MAIN RAIN
THREAT ALONG THE COAST AND OVER THE COASTAL WATERS THROUGH
MIDNIGHT AND THEN SHIFTS IT FARTHER INLAND AFTER THAT TIME AS THE
OUTFLOW BOUNDARY LIFTS NORTH. ADDITIONALLY... THERE/S STILL SOME
UNCERTAINTY ON HOW FAR NORTH AND EAST THE RAIN WILL ACTUALLY
DEVELOP OVERNIGHT AS THE PATH OF THE DISTURBANCE FROM MEXICO WILL
ALSO AFFECT WHICH AREAS SEE RAIN. FOR NOW... CONTINUING TO
HIGHLIGHT THE BEST RAIN CHANCES ALONG AND WEST OF INTERSTATE 45
TONIGHT. UPDATED PRODUCTS ALREADY OUT.

HUFFMAN

&&

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

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH THROUGH TUESDAY 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 MIDNIGHT CDT TONIGHT FOR THE
     FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY...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...14
AVIATION/MARINE...43

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
328 PM CDT MON MAY 11 2015

TXZ163-164-176>179-195>200-210>214-226-227-235>238-122030-
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-
328 PM CDT MON MAY 11 2015

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

HEAVY RAINFALL AND FLOODING HAS ALREADY OCCURRED FROM NAVASOTA TO
HUNTSVILLE WITH OTHER ISOLATED AREAS OF HIGHER RAINFALL AMOUNTS. A
FRONTAL BOUNDARY CONTINUES TO STALL ACROSS THE AREA WITH AN UPPER
LEVEL DISTURBANCE EXPECTED TO MOVE INTO THE AREA OVERNIGHT.
COMBINED WITH ABUNDANT MOISTURE FROM THE GULF...ADDITIONAL HEAVY
RAINFALL IS EXPECTED TO NIGHT. STORMS COULD PRODUCE 1 TO 2 INCHES
OF RAINFALL IN AN HOUR AND WITH SLOW MOVING STORMS...FLOODING
COULD RESULT. A FLASH FLOOD WATCH HAS BEEN ISSUED FOR THE
POTENTIAL OF FLOODING FROM THESE STORMS.

THERE IS STILL A SLIGHT RISK OF SEVERE STORMS TONIGHT BUT OVERALL
THINK STORMS MAY REMAIN BELOW SEVERE LEVELS. SHOULD A SEVERE STORM
DEVELOP...GUSTY WINDS AND HAIL WILL BE THE MAIN THREATS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THUNDERSTORMS CAPABLE OF PRODUCING HEAVY RAINFALL WILL BE POSSIBLE
TUESDAY AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE AREA. SOME
STORMS MAY PRODUCE 2 INCHES OF RAINFALL IN AN HOUR. WITH SLOW
MOVING STORMS THAT COULD BE MOVING OVER AREAS THAT HAVE ALREADY
RECEIVED HEAVY RAINFALL...THERE IS THE POTENTIAL FOR FLASH
FLOODING. A FLASH FLOOD WATCH HAS BEEN ISSUED THROUGH TUESDAY
EVENING. ADDITIONAL THUNDERSTORM ACTIVITY CAN BE EXPECTED
WEDNESDAY AND THURSDAY. AGAIN HEAVY RAINFALL AND FLOODING WILL BE
THE MAIN IMPACTS FROM THE STORMS. THE SEVERE WEATHER POTENTIAL
REMAINS LOW BUT A STRONG STORM COULD STILL PRODUCE GUSTY WINDS AND
FREQUENT LIGHTNING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TONIGHT.