Flash Flood Warning 4, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
633 PM CDT FRI MAY 14 2010

.DISCUSSION...
00Z TAF DISCUSSION.

&&

.AVIATION...
BROKEN LINE OF THUNDERSTORMS FROM JUST W OF KCXO/KUTS DOWN TO
KSGR AND THEN TO KVCT IS SLOWLY MOVING E WITH SOME CELLS MOVING N
OFF THE GULF. SOME OF THESE CELL MERGERS HAVE RESULTED IN
ENHANCED AREAS OF TSRA MAINLY OVER KSGR. RIGHT NOW THIS ACTIVITY
IS ANTICIPATED TO SLOWLY DRIFT OVER KIAH AND KHOU OVER THE NEXT
HOUR OR TWO. MAIN THREATS WILL BE HEAVY RAINFALL REDUCING VSBY TO
1SM OR LESS AND SOME BRIEF GUSTY WINDS FROM THE WNW. SUSPECT
CONVECTION WILL BEGIN TO WANE AROUND 01Z- 02Z AS INSTABILITY
DECREASES. BASED OFF 12Z WRF- ARW...THINK CONVECTION WILL SLOWLY
COME TO AN END AROUND 05Z. KEEP MVFR CIGS IN PLACE OVERNIGHT WITH
ENE-SE WINDS ACROSS THE AREA. TOMORROW WILL BE ANOTHER QUESTION
MARK WITH CONVECTION. WILL HAVE TO RE- EVALUATE THESE
POSSIBILITIES IN THE 06Z TAFS BUT COULD SEE ISO ACTIVITY DURING
THE DAY TOMORROW.

39

&&

.PREV DISCUSSION... /ISSUED 350 PM CDT FRI MAY 14 2010/

DISCUSSION...
A SLIGHTLY AMPLIFIED ZONAL PATTERN WILL BE OVER SE TX THROUGH THE
NEXT SEVEN DAYS. ALMOST DAILY SHORTWAVE TROUGHS WILL MOVE ACROSS THE
AREA AND KEEP CHANCES OF RAIN IN PLACE. THE MODELS ARE DIFFERING IN
THEIR SOLUTIONS WHICH HAS ADDED TO THE UNCERTAINTY. DID NOT FEEL
CONFIDENT ENOUGH TO INSERT LIKELY POPS BEYOND THE FIRST PERIOD. THE
MAIN FRONTAL BOUNDARY WILL BE NORTH TOWARD THE RED RIVER AREA AND THE
SURFACE BOUNDARIES OVER SE TX WILL BE MESO-SCALE DRIVEN.

THE MAIN FORECAST CONCERN FOR THIS EVENING IS THE STRENGTH OF THE
THUNDERSTORMS ENTERING THE AREAS WEST OF INTERSTATE 45. ALTHOUGH
THERE MAY BE SMALL HAIL AND STRONG GUSTY WINDS...LOCALLY HEAVY
RAINFALL LOOKS TO BE THE BIGGEST THREAT. THE DRY ANTECEDENT
CONDITIONS WAS REFLECTED IN THE GRIDDED FLASH FLOOD GUIDANCE OF ABOUT
3 TO 5 INCHES PER HOUR. ONE HOUR PRECIP RATES SO FAR HAS BEEN ONE
TO THREE INCHES PER HOUR. HOWEVER...SOME AREAS JUST WEST THE JACKSON
COUNTY LINE WERE 3 TO 3.5 INCHES PER HOUR. RAINFALL RATES MAY GET
HIGH ENOUGH TO GENERATE MINOR STREET FLOODING AND WILL ADJUST THE
HAZARDOUS WEATHER OUTLOOK TO REFLECT THIS.

OVER THE WEEKEND...BETTER CHANCES FOR RAIN LOOK TO OCCUR SATURDAY
THAN SUNDAY. THE ECMWF INDICATED AT LEAST A SLIGHT CHANCE FOR RAIN
THROUGH THE NEXT WORK WEEK.

40

MARINE...
SCATTERED SHOWERS WILL BE POSSIBLE FRIDAY AFTERNOON ACROSS THE
COASTAL WATERS WITH THE GREATEST CONCENTRATION IN THE BAYS AND WEST
OF A LINE FROM FREEPORT SOUTHWARD. ONSHORE WINDS EXPECTED THROUGHOUT
MUCH OF THE UPCOMING WEEK WITH WAVE HEIGHTS DECLINING BY SUNDAY
EVENING. 38

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      69  87  70  85  70 /  40  40  30  30  30
HOUSTON (IAH)              69  87  70  87  69 /  60  40  30  30  30
GALVESTON (GLS)            74  82  75  82  74 /  50  40  30  30  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION THROUGH SATURDAY AFTERNOON
     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.

&&

AVIATION/MARINE...39

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
411 PM CDT FRI MAY 14 2010

GMZ330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-
227-235>238-151300-
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-
411 PM CDT FRI MAY 14 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...TONIGHT

THUNDERSTORMS WILL MOVE ACROSS SOUTHEAST TEXAS THIS EVENING. A
FEW OF THE STORMS MAY GENERATE MINOR FLOODING...ESPECIALLY OVER
URBAN LOCATIONS. RAINFALL OF ONE TO TWO INCHES CAN BE EXPECTED
WITH ISOLATED AMOUNTS OF TWO TO FOUR INCHES POSSIBLE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.