Hail and Damaging Winds in Texas, April 20, 2006

AREA FORECAST DISCUSSION...UPDATE AVIATION AND MARINE
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
400 PM CDT THU APR 20 2006

.DISCUSSION...
CONVECTION/WATCH BOXES GETTING CLOSER THIS AFTN...BUT CURRENT TRA-
JECTORY OF STORMS AND SLIGHT SHIFT OF THE SFC BOUNDARY NORTH COULD
GIVE US SOME BREATHING ROOM (ATTM). HOWEVER...WE ARE STILL LOOKING
AT VERY GOOD POPS TONIGHT AS MODELS CONTINUE WITH THE DEVELOPMENT/
MOVEMENT OF AN MCS OVERNIGHT FROM CNTL TX ACROSS INTO E/SE TX THRU
SUNRISE. DEEPEST MOISTURE/LOWEST INSTABILITIES POOLING ALONG THE E
-W SFC BOUNDARY JUST NORTH OF THE CWFA...BUT WILL GO AHEAD AND THE
MENTION OF SEVERE FOR ALL OUR ZONES TONIGHT/EARLY FRI MORN. ROBUST
DYNAMICS/STRONG LLJ SHOULD OVERCOME THE SLIGHTLY STRONGER CAP THAT
HAS BEEN LINGERING AOA THE COAST. NOT MUCH ELSE TO ADD TO SPC DIA-
LOGUE/OUTLOOK FOR TONIGHT. WEAK FRONT TO SWEEP THRU IN THE WAKE OF
TONIGHTS ACTIVITY WITH SLIGHTLY LOWER DEWPOINTS TOMORROW. BUT S/SE
WINDS TO RETURN BY SAT. OTHERWISE THE BUILDING UPPER RIDGE TO KEEP
TEMPS JUST ABOVE SEASONAL NORMS THIS WEEKEND. GFS STILL GOING WITH
SOME LIFT/POPS MON AS A S/W INTERACTS WITH THE DRYLINE AND MOVES E
WITH TIME AS THE RIDGE BREAKS DOWN. THIS FLATTISH RIDGE PROGGED TO
HOLD MOST OF NEXT WEEK WITH MODELS STARTING TO DIVERGE ON THE TREK
AND MOVEMENT OF THE NEXT UPPER TROF. HOWEVER BOTH STILL HOLDING ON
TO THE IDEA OF A FRONT NEXT WED.
41

&&

.MARINE...
MODERATE ONSHORE WINDS THROUGH TONIGHT AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURES OVER NORTHERN TEXAS. MESO-SCALE BOUNDARIES
FROM INLAND THUNDERSTORM DOWNDRAFTS MAY INTERRUPT AND OR MODIFY THIS
PREDOMINANT ONSHORE FLOW IF CONVECTION OVER OUR NORTHERN COUNTIES
BECOMES MORE INTENSE OVERNIGHT. WINDS WILL DECREASE FRIDAY NIGHT AS
A WEAK LARGE SCALE TROUGH APPROACHES THE COAST. NORTHEAST WINDS LATE
FRIDAY NIGHT WILL BECOME EASTERLY AS HIGH PRESSURE BUILDS EAST.
ONSHORE FLOW RESUMES LATE SUNDAY THROUGH TUESDAY. ANOTHER FRONT TO
SHIFT WINDS MORE OFFSHORE POSSIBLE WEDNESDAY.
31

&&

.AVIATION...
MVFR THROUGH 6Z. HIGH PROBABILITY OF VCTS AFTER 6Z. WINDOW FOR MOST
ACTIVE CONVECTION WILL BE BETWEEN 7Z AND 18Z ACROSS MOST NORTH
CENTRAL TERMINALS AS MAIN COMPLEX OF THUNDERSTORMS AND SHOWERS
TRAVELS FROM HILL COUNTRY NORTHEAST TOWARDS SHREVEPORT. POTENTIAL
FOR SEVERE CONDITIONS WITH CLL IN TORNADO WATCH THROUGH 10 PM.
WHETHER THUNDERSTORMS GET ACT TOGETHER IN FORMING A MULTICELL LINE
AND TRAVELING THROUGH THE HOUSTON METRO HUBS WILL BE BETTER HANDLED
BY SWING SHIFT.
31

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      65  83  60  86  63 /  70  70  10   0   0
HOUSTON (IAH)              67  84  61  86  64 /  60  60  10   0   0
GALVESTON (GLS)            70  80  67  82  69 /  20  20  10   0   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
511 PM CDT THU APR 20 2006

TXZ163-164-176>179-195>200-210>214-226-227-235>238-211200-
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-
511 PM CDT THU APR 20 2006

...SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST TEXAS
TONIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST TEXAS.

.DAY ONE...REST OF TODAY AND TONIGHT
A TORNADO WATCH IS IN EFFECT UNTIL 10 PM CDT THIS EVENING FOR
BRAZOS, BURLESON AND WASHINGTON COUNTIES.

A STATIONARY FRONT JUST NORTHWEST OF THE AREA WILL COMBINE WITH A
VERY UNSTABLE AIRMASS IN PLACE TO PRODUCE SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS NORTHERN PORTIONS OF SOUTHEAST TEXAS THIS
EVENING. A FEW OF THESE STORMS COULD BECOME SEVERE TO THE NORTH OF A
LINE FROM COLUMBUS TO CONROE TO LIVINGSTON. THE PRIMARY SEVERE WEATHER
THREATS WILL BE DAMAGING WINDS AND LARGE HAIL...BUT ISOLATED TORNADOES
ARE ALSO POSSIBLE.

HOWEVER...THE MAIN SEVERE WEATHER THREAT FOR SOUTHEAST TEXAS EXISTS
DURING THE OVERNIGHT HOURS TONIGHT. A COMPLEX OF STRONG TO SEVERE
THUNDERSTORMS IS EXPECTED TO FORM OVER CENTRAL TEXAS LATE THIS
AFTERNOON INTO EARLY EVENING AS A STRONG UPPER LEVEL DISTURBANCE
APPROACHES FROM THE WEST. THIS COMPLEX OF THUNDERSTORMS IS EXPECTED TO
MOVE INTO THE WESTERN AND NORTHERN COUNTIES OF SOUTHEAST TEXAS DURING
THE LATE EVENING AND OVERNIGHT HOURS TONIGHT. THE PRIMARY SEVERE
WEATHER THREATS WILL BE DAMAGING WINDS AND LARGE HAIL. AGAIN...THE
PRIMARY THREAT AREA WILL BE NORTH OF A LINE FROM COLUMBUS TO CONROE TO
LIVINGSTON. HOWEVER...SEVERE WEATHER COULD EXTEND FURTHER SOUTH
TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY
FRIDAY...STRONG TO SEVERE THUNDERSTORMS MAY BE ONGOING EARLY IN
THE DAY BUT WILL LIKELY DISSIPATE AS THE MORNING PROGRESSES.
ISOLATED THUNDERSTORMS MAY REDEVELOP DURING THE AFTERNOON AS A
WEAK COLD FRONT INTERACTS WITH DAYTIME HEATING. THE POTENTIAL
EXISTS FOR A FEW OF THESE STORMS TO BECOME SEVERE. THE SEVERE
WEATHER THREAT WILL END BY EARLY EVENING.

SATURDAY THROUGH WEDNESDAY...NO HAZARDOUS WEATHER IS ANTICIPATED
AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL LIKELY BE NEEDED THROUGH TONIGHT OVER THE
NORTHERN PORTIONS OF SOUTHEAST TEXAS. SPOTTER ACTIVATION MAY BE NEEDED
FOR THE REST OF SOUTHEAST TEXAS LATER TONIGHT.