DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 201933
SWODY1
SPC AC 201931

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0131 PM CST FRI NOV 20 2009

VALID 202000Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...SOUTH TX/LOWER TX COAST...
MADE TWO CHANGES FOR THE 20Z OUTLOOK. THE FIRST IS TO REMOVE THE 5
PERCENT HAIL PROBABILITY. WEAK LAPSE RATES AND INSTABILITY SHOULD
LIMIT THE HAIL POTENTIAL ACROSS SOUTH TX. THE SECOND IS TO TRIM THE
WRN EDGE OF THE 5 PERCENT WIND AND 2 PERCENT TORNADO PROBABILITIES
TO ALIGN WITH THE COLD FRONT AND ONGOING CONVECTION. REGIONAL
WSR-88D VWPS AND OBJECTIVE ANALYSIS ALONG THE LOWER TX COAST
CONTINUE TO SHOW 0-6 KM SHEAR VALUES RANGING FROM 50 KT IN THE
BROWNSVILLE AREA TO AROUND 70 KT IN THE CORPUS CHRISTI AREA. IN
SPITE OF WEAK INSTABILITY...THE STRONG VERTICAL SHEAR MAY SUPPORT A
MARGINAL SEVERE THREAT WITH THE MORE INTENSE CELLS THIS AFTERNOON
BEFORE THE FRONT MOVES OFFSHORE.

..BROYLES.. 11/20/2009

.PREV DISCUSSION... /ISSUED 1017 AM CST FRI NOV 20 2009/

...SYNOPSIS...
WEAK LONGWAVE RIDGING WAS LOCATED OVER THE ROCKIES...WITH A BROAD
TROUGH MOVING EWD ACROSS THE CENTRAL PORTIONS OF THE COUNTRY. THE
ONLY CONVECTIVE AREA OF INTEREST FOR POSSIBLE SEVERE STORMS TODAY
WILL BE ASSOCIATED WITH AN EMBEDDED SHORTWAVE TROUGH LOCATED ON THE
SRN END OF THE LARGER SCALE TROUGH...OVER THE BIG BEND AREA OF
TEXAS.

...SRN TX...
AT MID MORNING...ELEVATED THUNDERSTORMS STRETCHED FROM NEAR SAT TO
LRD...AND APPEARED TO BE OCCURRING WITHIN REGION OF STRONGER FORCING
ALOFT. THESE STORMS ARE LIKELY TO INTENSIFY AS THEY SPREAD EWD
THROUGH THE DAY INTO A SLOWLY WARMING AND DESTABILIZING AIR MASS. AS
TEMPERATURES WARM INTO THE MID/UPPER 70S...STORMS MAY BECOME SURFACE
BASED BY MID AFTERNOON...ESPECIALLY ALONG AND EAST OF A NIR-MFE
LINE. MUCAPES BETWEEN 1000-2000 J/KG AND 30-40 KT DEEP LAYER SHEAR
MAY BE SUFFICIENT FOR AN ISOLATED SEVERE STORM OR TWO...WITH
MARGINAL SEVERE HAIL/WIND GUSTS. HOWEVER...SEVERE PROBABILITIES
REMAIN LOW DUE TO EXTENSIVE CLOUDS...WEAK WINDS IN THE LOWER 2-3 KM
AND STRONGER CONVECTION/INSTABILITY SITUATED EAST OF THE MAINLAND IN
THE WRN GULF.

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