Flash Flood Warning 79, NWS Houston/Galveston, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
945 AM CST SUN NOV 21 2004

DISCUSSION...

...A DANGEROUS AND LIFE THREATENING FLOOD EVENT UNFLODING ACROSS
PARTS OF SOUTHEAST TEXAS...

STORMS CONTINUE TO CLUSTER OVER PARTS OF WHARTON...JACKSON AND
COLORADO COUNTIES. KHGX-88D IS OVERESTIMATING A BIT...IT APPEARS
THAT WHARTON COUNTY HAS RECEIVED IN EXCESS OF 12 INCHES OF RAIN
SINCE LAST NIGHT. MANY HOMES ARE INUNDATED AND ROADS ARE IMPASSABLE
DUE TO HIGH WATER.

THE BOUNDARY RESPONSIBLE FOR THESE TRAINING STORMS IS NEARLY
STATIONARY AND DOES NOT APPEAR TO BE MOVING NORTH AT ALL. LATEST RUC
MODEL KEEPS THE BNDRY IN PLACE WITH CONVECTION FIRING ALONG AND JUST
NORTH OF IT THROUGH EVENING. PWS ARE NEARLY 200 PERCENT OF NORMAL
AND THERE IS DECENT UPPER LEVEL VENTILATION PER SATELLITE IMAGES.
WILL MANTAIN FLOOD WATCH TODAY. PREVIOUS FCST HAS THINGS COVERED
NICELY AND NO CHANGES ARE REQUIRED. 43

&&

SLOW NORTHWARD MOVING WARM FRONTAL BOUNDARY EXTENDING FROM NEAR EDNA
TO HOUSTON TO NEAR MOSS HILL. STRONG ISENTROPIC LIFTING ESPECIALLY SW
ZONES PRODUCING COPIOUS RAINFALL. FLASH FLOOD WARNINGS CONTINUING OVER
JACKSON/WHARTON COUNTIES EARLY THIS MORNING WHERE STRONG CLUSTER OF
THUNDERSTORMS PERSISTS. PWATS OVER CWFA ABOUT 1.5 TO 1.6 INCHES.
FLOOD DECISION TREE AND PRECIP ESTIMATE OBVIOUSLY POINT TO FLOODING
POTENTIAL FOR OUR REGION TODAY. WITH SOIL QUITE SATURATED FROM
RAINFALL THE PAST FEW DAYS...AND ANTICIPATED CONTINUING WIDESPREAD
RAINFALL OVER CWFA...WE SHALL ISSUE A FLOOD WATCH SHORTLY FOR TODAY.
WARM AIR AND MOISTURE ADVECTION BOTH EVIDENT AT 850 AND 700 MB
LEVELS (WITH GOOD INFLOW AT 850 MB).  MODELS SHIFTING FOCUS OF
RAINFALL TO THE NORTHWEST TONIGHT. WARM FRONTAL BOUNDARY EXPECTED TO
GRADUALLY PUSH NORTH TODAY. THIS SHOULD SHIFT RAINFALL FOCUS TO
NORTHERN ZONES BUT STILL A GOOD CHANCE AREAWIDE WITH HIGH PWATS AND
UPPER LEVEL JET NEARBY. THIS SCENARIO WILL CONTINUE THROUGH EARLY
NEXT WEEK. UPPER LOW WILL MOVE TO WEST TEXAS EARLY TUESDAY AND THEN
RAPIDLY SWING NORTHEAST WHILE OPENING INTO A TROUGH.  DRYING WEST TO
EAST EXPECTED BY TUESDAY AFTERNOON. COLD FRONT WILL PUSH THROUGH
REGION TUESDAY NIGHT. WEDNESDAY AND REST OF WEEK WILL SEE DRY AND
COOL WEATHER. A COLD FRONT IS INDICATED BY GFS TO MOVE ACROSS TEXAS
SUNDAY.

AVIATION...EXPECT SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS OVER
CWFA TODAY WITH CEILINGS AT OR SLIGHTLY BELOW IFR CONDITIONS.
VISIBILITIES TEMPORARILY LOWERING TO BELOW IFR CONDITIONS IN
PASSING SHOWERS.

MARINE...WE SHALL HAVE CAUTION FOR BAYS AND 0-20 NM COASTAL WATERS
WITH SCA 20-60 COASTAL WATERS. SOUTH TO SOUTHEAST WINDS HAS BEEN
INCREASING IN RESPONSE TO TIGHTENING OF PRESSURE GRADIENT NEAR THE
COAST. WAVE HEIGHTS GRADUALLY INCREASING THE LAST FEW HOURS AND NOW
RUNNING 5 FEET 20-60 NM REGION.

37/45
&&

.HGX WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH ALL HGX CWFA UNTIL 6 PM TODAY.
SCEC BAYS AND 0-20 NM COASTAL WATERS.
SCA 20-60 NM COASTAL WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 73 66 74 66 73 / 80 80 60 80 70
HOUSTON (IAH)         77 68 76 68 76 / 80 60 50 60 70
GALVESTON (GLS)       78 72 77 71 78 / 80 40 30 50 70

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
455 AM CST SUN NOV 21 2004

TXZ163-164-176>179-195>200-210>214-226-227-235>238-221200-
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-
455 AM CST SUN NOV 21 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

...FLOOD WATCH IN EFFECT THROUGH 6 PM TODAY...

.DAY ONE...TODAY AND TONIGHT
A FLOOD WATCH IS IN EFFECT TODAY FOR ALL OF SOUTHEAST TEXAS. PLEASE
REFER TO THE LATEST FLOOD BULLETIN (FFAHGX) FOR DETAILS.

A WARM FRONT WILL SLOWLY MOVE NORTH ACROSS THE REGION. THE WARM
FRONT IN COMBINATION WITH PASSING UPPER LEVEL DISTURBANCES...WILL
RESULT IN WIDESPREAD SHOWERS AND THUNDERSTORMS. WITH THE SOIL
ALREADY SATURATED...ADDITIONAL HEAVY RAINFALL WILL EASILY RUNOFF
LEADING TO POSSIBLE FLOODING. THE FLOOD WATCH MAY BE EXTENDED
THROUGH TONIGHT UPON FURTHER ASSESSMENT OF THE WEATHER SITUATION.

ALONG WITH THE THREAT OF FLOODING...SOME THUNDERSTORMS MAY BECOME SEVERE
ESPECIALLY NEAR THE WARM FRONT.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.
THROUGH TUESDAY...ADDITIONAL RAINFALL ACCUMULATIONS OF 1 TO 3
INCHES WITH ISOLATED TOTALS APPROACHING 5 INCHES WILL BE POSSIBLE.
WITH THE GROUND ACROSS MUCH OF SOUTHEAST TEXAS ALREADY SATURATED...
A CONTINUED FLOOD THREAT IS POSSIBLE. SEVERE THUNDERSTORMS MAY ALSO
DEVELOP ACROSS SOUTHEAST TEXAS AND THE ADJACENT COASTAL WATERS. THE
MAIN THREAT WILL PROBABLY BE STRONG DAMAGING WINDS AND ISOLATED
TORNADOES.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED TODAY AND POSSIBLY...TONIGHT.