Severe Thunderstorm Warning 23, NWS Houston/Galveston, TX

SOUTHEAST TEXAS FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
910 AM CST THU MAR 13 2003

SURROUNDING SOUNDINGS INDICATE HIGHLY UNSTABLE AIR MASS OVER REGION
...MOIST TO ABOUT 700 MB AND QUITE DRIER ABOVE. TOTAL TOTALS AT 61
AND CAPE NEAR 3600 J/KB. UPDATED 1ST PERIOD OF ZFPHGX TO REFLECT
CURRENT TRENDS INCLUDING SPC ISSUANCE OF SVR TSTM WATCH NUMBER 38.
EXPECT LOCALLY HEAVY RAIN FROM SLOWER MOVING STORMS. HAVE ADJUSTED MAX
TEMPS SLIGHTLY DOWNWARD.

.HGX...NPW FOR DENSE FOG ALONG AND SOUTH OF A LINE FROM LIVINGSTON TO
       CONROE TO BELLVILLE THRU 10 AM.
       SEVERE THUNDERSTORM WATCH PORTIONS OF SOUTHEAST TEXAS TIL 2
       AM.

CLL TB 079/059 077/054 078 531
IAH TB 079/060 077/055 078 631
GLS TB 074/064 072/061 073 642

PREVIOUS DISCUSSION...
QUITE A RANGE OF CEILING HEIGHTS AND VSBYS TONIGHT ACROSS SE TX. DENSE
FOG IS GENERALLY CONFINED TO THE COASTAL COUNTIES WITH LIGHT FOG
INLAND. HOWEVER DWH JUST REPORTED DENSE FOG. THEREFORE WILL GO AHEAD
AND LEAVE CURRENT ADVISORY AS IS AND CANCEL LATER THIS MORNING FOR
PORTIONS OF THE AREA IF DENSE FOG DOES NOT DEVELOP FURTHER INLAND.

MAIN FORECAST ISSUE IS THE CHC OF SVR TSTMS TODAY AND EARLY THIS
EVENING. APPEARS THAT ALL OF THE INGREDIENTS ARE COMING TOGETHER FOR
A THREAT OF SVR TSTMS AREAWIDE. CONVECTION CURRENTLY ALONG THE RED
RIVER WILL CONTINUE TO PUSH S-SE AND WILL LIKELY AT LEAST PROVIDE A
BOUNDARY FOR CONVECTIVE DEVELOPMENT ACROSS SE TX IN A VERY MOIST AND
UNSTABLE ATMOSPHERE. IN FACT...AM CONCERNED THAT IT WILL HOLD TOGETHER
AND MOVE INTO NORTHERN PORTIONS OF SE TX LATER THIS MORNING. LIS
ARE LIKELY TO BE IN THE -6 TO -9 RANGE LATER TODAY AS MID-LEVELS
COOL WITH MID-UPPER LEVEL TROF AMPLIFYING AND EXTENDING BACK INTO SE
TX. FLOW AT THE MID-LEVELS WILL BECOME MORE NORTHERLY DURING THE DAY
WHICH WILL AID IN A SOUTHWARD PROPAGATION DURING THE
AFTERNOON...WHICH MEANS ENTIRE AREA WILL BE UNDER THE GUN TODAY. SE
TX WILL BE IN THE LF QUAD OF AN UPPER LEVEL JET MAX WHICH WILL
PROVIDE SOME ADDITIONAL DIVERGENCE ALOFT. MODEL SOUNDINGS SHOW
MID-LEVEL DRY AIR WHICH WILL ENHANCE CONVECTIVE DOWNDRAFTS.
THEREFORE...AGREE WITH SPC SLIGHT RISK OUTLOOK. BELIEVE THE THREAT
WILL EXTEND INTO THE EARLY EVE HOURS...ESPECIALLY FOR SOUTHERN
ZONES...SO WILL HAVE HIGHEST 2ND PD POPS THERE. MAIN THREATS WILL BE
HAIL AND STRONG WIND GUSTS.

WILL HAVE HIGHEST POPS ACROSS EASTERN ZONES WHERE SLIGHTLY DEEPER
MOISTURE AND BETTER LIFT WILL BE PRESENT. POPS HAVE BEEN TRENDED
CLOSE TO MESO-ETA MODEL. BELIEVE WITH PW VALUES REACHING CLOSE TO
1.5 INCHES...LOCALLY HEAVY RAINFALL IS A THREAT. WILL PROBABLY
ADDRESS THIS IN THE HAZARDOUS WEATHER OUTLOOK AND LEAVE OUT OF ZONES
AS PRIMARY THREAT APPEARS TO BE SVR TSTMS. WILL KEEP A 20 PERCENT
CHC ALONG THE COAST ON FRIDAY...WHERE MOISTURE LEVELS WILL STILL BE
DEEP ENOUGH FOR PRECIP DEVELOPMENT...FURTHER INLAND WILL DROP POPS.
BELIEVE ATMOSPHERE WILL GRADUALLY DRY LATER TONIGHT AND THROUGH
FRIDAY IN THE WAKE OF THE TROUGH AND NE SFC FLOW. THEREFORE WILL
DROP POPS THIS WEEKEND ACROSS MOST OF THE AREA. THERE MAY BE A FEW
SHOWERS ACROSS WESTERN AREAS SUN AFT.

MODELS STILL SHOW A SIGNIFICANT STORM SYSTEM AFFECTING SE TX MON AND
TUE AS AN IMPRESSIVE TROUGH MOVES FROM THE WEST COAST TO THE CENTRAL
U.S. WILL KEEP CHC POPS FOR THESE DAYS.

33/46

TXZ163-164-176>179-195>200-210>214-226-227-235>238-141300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
700 AM CST THU MAR 13 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST TEXAS.

...SEVERE THUNDERSTORMS AND LOCALLY HEAVY RAINFALL POSSIBLE TODAY AND
THIS EVENING ACROSS ALL OF SOUTHEAST TEXAS...

.DAY ONE...TODAY AND TONIGHT.

A DENSE FOG ADVISORY IS IN EFFECT UNTIL 10 AM FOR AREAS GENERALLY
ALONG AND SOUTH OF A LINE FROM LIVINGSTON TO CONROE TO BELLVILLE.

A VERY MOIST AND UNSTABLE ATMOSPHERE IS IN PLACE OVER SOUTHEAST TEXAS
TODAY. AN APPROACHING UPPER LEVEL DISTURBANCE AND BOUNDARY FROM
THUNDERSTORMS ACROSS NORTHERN PORTIONS OF SOUTHEAST TEXAS THIS
MORNING WILL TRIGGER THUNDERSTORM DEVELOPMENT OVER THE AREA TODAY.
SEVERE THUNDERSTORMS ARE POSSIBLE DUE TO THE VERY COLD TEMPERATURES
AND DRY AIR IN THE MIDDLE LAYER OF THE ATMOSPHERE. THE PRIMARY
SEVERE WEATHER THREATS WILL BE LARGE HAIL AND DAMAGING WIND GUSTS.

LOCALLY HEAVY RAINFALL WILL BE A THREAT DUE TO SLOW MOVING STORMS AND
VERY HIGH MOISTURE LEVELS. RAINFALL AMOUNTS ARE EXPECTED TO AVERAGE A
HALF TO ONE INCH ACROSS THE AREA WITH ISOLATED AMOUNTS OF THREE INCHES
POSSIBLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED LATER TODAY.