Severe Thunderstorm Warning 155, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
230 PM CDT TUE SEP 5 2000

PARTLY CLOUDY WITH RECORD BREAKING HEAT OVER SERN TX AGAIN
EARLY THIS AFTERNOON. THE FRONT IS MAKING SLOW PROGRESS AND IS ALONG
A TPL/UTS/LCH LINE. THE MAIN FORECAST ISSUES ARE CHANCE OF SEVERE
CONVECTION THIS AFTERNOON/TONIGHT...THEN TEMPS/POPS THROUGH THE
REMAINING PERIODS. THE 12Z NCEP MODELS ARE IN FAIR AGREEMENT WITH
THE SYNOPTIC FEATURES...BUT PREFER THE ETA AS PRIMARY SOLUTION WITH
SOME BLENDING FROM THE AVN FOR TEMPS. AGREE WITH HPC PMDEPD THAT MRF
SEEMS OVERDONE WITH POPS IN THE MEDIUM RANGE PERIOD.

THERE IS STILL CONCERN AND QUESTION AS TO IF...WHERE...AND WHEN
CONVECTION WILL FIRE. BASIC PLAN IS BACK OFF A BIT FROM THE
MID-MORNING UPDATE...BUT STILL CARRY 20-30 POPS MOST PLACES WITH
MICROBURST SEVERE THREAT WORDING. THE SITUATION GETS VERY
INTERESTING WED AS THE LOWER LEVELS REMAIN UNSTABLE ENOUGH TO
PRODUCE CONVECTION ALONG THE THEN STALLED BOUNDARY...BUT WILL
CAPPING BE ENOUGH TO LIMIT THINGS TO FAIR WX CU OR JUST SHOWERS.
PLAN TO HANDLE THIS WITH A LESS THAN 20 POP FOR THE COASTAL ZONES
AND LET THE NEXT SHIFT ADJUST AS NECESSARY.

GIVEN THE SFC HIGH CENTER IS ALREADY NEAR LAKE HURON...THE COOLER
AIR WILL ONLY KNOCK RECORD HEAT DOWN TO "HOT"...ESPECIALLY IN THE
SWRN 1/2 OF THE AREA...WHERE THE HEAT ADVISORY LOOKS GOOD FOR
ANOTHER DAY. SIMILARLY...BREEZY WINDS AND REDUCED HUMIDITY INDICATE
MAINTAINING THE RED FLAG WARNING ON WED. WILL HAVE THE NEXT SHIFT
EVALUATE THE NEED FOR THESE...THEY COULD BE DROPPED IN THE EARLY AM
WED PACKAGE.

WILL PLAY TEMPS ON AN ETA/MAV BLEND THROUGH THE SHORT TERM...THEN GO
A CATEGORY ABOVE MEX GUIDANCE IN THE EXTENDED. IN CONTRAST...WILL
DROP MEX POPS ONE CATEGORY EXCEPT FOR SAT...WHEN THE WEAK WAVE COMES
ASHORE WITH HIGH PW AIR.

.KHGX...HEAT ADVISORY WEST OF I-45 FOR WEDNESDAY.
        RED FLAG WARNING ALL ZONES TONIGHT AND WEDNESDAY.

31/47

PRELIMS...
CLL UB 072/100 072/095 070 200
IAH UB 070/099 073/093 073 221
GLS UB 079/090 078/088 078 222

RECORDS FOR WED 9/6
CLL  104/1913
IAH   97/1999
GLS   94/1912

TXZ163-164-176>179-195>200-210>214-226-227-235>238-060200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
345 PM CDT TUE SEP 5 2000

...ISOLATED SEVERE THUNDERSTORMS POSSIBLE WITH DAMAGING MICROBURST
WINDS LATE THIS AFTERNOON AND THIS EVENING...
...DANGEROUS HEAT AGAIN ON WEDNESDAY...
...RED FLAG WARNING THROUGH WEDNESDAY FOR HIGH FIRE DANGER...

ISOLATED SEVERE THUNDERSTORMS WITH DAMAGING WINDS ARE POSSIBLE LATE
THIS AFTERNOON AND THIS EVENING MAINLY SOUTH OF A COLLEGE STATION TO
TO HUNTSVILLE TO LIVINGSTON LINE. THE MAIN THREAT TIME IS FROM 4 PM
TO 9 PM. AN UNSTABLE ATMOSPHERE WITH DRY AIR IN THE LOWEST LAYERS
INDICATES THUNDERSTORMS ARE CAPABLE OF PRODUCING STRONG DAMAGING
WINDS...POSSIBLY WITH NO INDICATION ON RADAR AND HENCE LITTLE OR NO
WARNING.

RECORD BREAKING TEMPERATURES OCCURRED ONCE AGAIN THIS AFTERNOON. ON
WEDNESDAY...HIGH TEMPERATURES WILL LIKELY APPROACH THE CENTURY MARK
INLAND AND THE LOWER 90S AT THE COAST. HEAT INDICES COULD REACH THE
108 TO 112 DEGREE RANGE AT LOCATIONS GENERALLY WEST OF I-45.

RELIEF APPEARS TO BE ON THE WAY. THE PERSISTENT STRONG RIDGE OF HIGH
PRESSURE ALOFT SHOULD MOVE NORTH AND A WEAK COLD FRONT WILL MOVE
THROUGH TONIGHT AND WEDNESDAY. READINGS SHOULD FALL TO MORE
SEASONABLE LEVELS THURSDAY AND FRIDAY.

IF POSSIBLE...REMAIN IN AN AIR-CONDITIONED AREA. IF YOU
MUST GO OUTSIDE...IT IS BEST TO DO SO THIS MORNING. WHETHER OUTSIDE
DURING THE MORNING OR AFTERNOON...SEEK SHADE AND TAKE FREQUENT
BREAKS. THE UPPER LEVEL RIDGE OF HIGH PRESSURE RESPONSIBLE FOR THE
HEAT WILL SLOWLY RETREAT NORTH AND WEST AND WEAKEN ON
WEDNESDAY...STARTING A GRADUAL COOLING TREND. HOWEVER...LATE SUMMER
ABOVE NORMAL TEMPERATURES ARE EXPECTED TO PERSIST INTO THE WEEKEND.

A RED FLAG WARNING IS IN EFFECT FOR ALL OF SOUTHEAST TEXAS THROUGH
WEDNESDAY. THE CURRENT EXTREME DROUGHT HAS DRIED OUT VEGETATION...
RESULTING IN VERY FLAMMABLE FUEL MATERIAL FOR WILDFIRES. WINDS WILL
ALSO BE A BIT STRONGER THAN THE PAST SEVERAL DAYS DUE TO THE PASSING
COLD FRONT. OUTDOOR BURN BANS ARE IN EFFECT AS A SAFETY PRECAUTION
FOR ALL OF SOUTHEAST TEXAS.

A RED FLAG WARNING IS ISSUED IN COORDINATION WITH THE USDA FOREST
SERVICE WHEN LOW HUMIDITY...STRONG WINDS...AND EXTREMELY DRY
VEGETATION GREATLY INCREASES THE RISK FOR WILDFIRE IGNITION AND
SPREAD. THE USUAL CRITERIA FOR A RED FLAG WARNING ARE:

1. RELATIVE HUMIDITY OF 20 PERCENT OR LESS.
2. WINDS OF 15 TO 25 MPH OR HIGHER.
3. LOW VEGETATION MOISTURE AS DETERMINED BY THE USDA FOREST SERVICE

AN EXACERBATING FACTOR IS DRY DAMAGING WINDS PRODUCED FROM
THUNDERSTORMS. THESE STRONG DOWNDRAFTS CAN REACH SPEEDS OF 50 TO 100
MPH CAUSING EXISTING FIRES TO FLARE UP. IN ADDITION...THE DRY AIR
CAN TOTALLY EVAPORATE RAIN FALLING FROM THE THUNDERSTORM...ALLOWING
LIGHTNING TO START NEW FIRES. PERSONS ACROSS SOUTHEAST TEXAS SHOULD BE
ON THE LOOKOUT FOR FIRES THE NEXT FEW DAYS AND CURTAIL ACTIVITIES THAT
COULD START FIRES...SUCH AS COOKING OUTDOORS AND OPERATING EQUIPMENT
CAPABLE OF IGNITING FIRES.

FURTHER INFORMATION ON THE FIRE WEATHER THREAT CAN BE FOUND ON THE
INTERNET AT HTTP://TXFORESTSERVICE.TAMU.EDU OR BY PHONE AT
1-877-258-5973.