Monday, October 26, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 261243
SWODY1
SPC AC 261241

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0741 AM CDT MON OCT 26 2009

VALID 261300Z - 271200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
SRN PART OF ELONGATED SHORTWAVE TROUGH NOW EXTENDING FROM THE CNTRL
PLNS TO THE SRN RCKYS EXPECTED TO AMPLIFY SE INTO CNTRL AND E TX
THIS PERIOD IN RESPONSE TO JET STREAK NOW MOVING S ACROSS WRN CO/NM.
AS THIS AMPLIFICATION OCCURS...STRONGER UPSTREAM DISTURBANCE NOW
APPROACHING 130W SHOULD CONTINUE RAPIDLY SE INTO THE WRN GRT BASIN.
THE RESULTING SHORTENED WAVE LENGTH BETWEEN THIS WRN SYSTEM AND THE
ONE OVER TX WILL FORCE THE TX SYSTEM TO ASSUME A NEUTRAL OR POSSIBLY
SLIGHTLY NEGATIVE TILT BY 12Z TUE.

AT THE SFC...COLD FRONT/PREFRONTAL OUTFLOW BOUNDARY NOW OVER TX AND
THE ARKLATEX WILL CONTINUE SSE ACROSS THE REMAINDER OF TX THROUGH
THIS EVE. EWD PROGRESS OF THE BOUNDARIES WILL...HOWEVER...BE
CONSIDERABLY SLOWER OVER THE SABINE RVR VLY...FAR WRN LA AND THE
NWRN GULF OF MEXICO. SFC WAVE DEVELOPMENT SHOULD OCCUR ALONG THE
STALLED FRONT AND/OR OUTFLOW BOUNDARY OVER THE FAR NWRN GULF EARLY
TUE AS AMPLIFYING UPR TROUGH APPROACHES REGION.

...SRN AND SE TX INTO SRN LA...
SCTD TO BKN TSTMS EXPECTED TO CONTINUE ALONG COLD FRONT/OUTFLOW
BOUNDARY ACROSS SRN AND SE TX THROUGH THE DAY. SCTD STORMS LIKELY
WILL ALSO PERSIST INVOF DIFFUSE NNW/SSE WARM FRONT NOW OVER THE
MIDDLE TX GULF CST. AND...ISOLD TO WDLY SCTD STORMS MAY FORM OVER
DEEP S TX THIS AFTN AS SFC HEATING FURTHER DESTABILIZES SEASONABLY
MOIST WARM SECTOR /PW AOA 1.75 INCHES/. MID LVL LAPSE RATES ACROSS
THE REGION WILL..HOWEVER...REMAIN WEAK...AS WILL LARGE SCALE FORCING
FOR ASCENT. COUPLED WITH THE UNDERCUTTING NATURE OF THE COLD
FRONT...EXPECT THAT ANY SVR THREAT WILL REMAIN ISOLD...LIMITED TO A
LOCALLY DMGG WIND GUST OR TWO...AND/OR A BRIEF TORNADO. THE
GREATEST SUCH RISK SHOULD EXIST ALONG THE MIDDLE TX GULF CST SWD
INTO DEEP S TX...WHERE SBCAPE MAY REACH 1500 J/KG AMIDST 35+ KT DEEP
SWLY SHEAR.

A SEPARATE CONDITIONAL RISK FOR ISOLD SVR WX MAY EVOLVE EARLY TUE IN
SRN LA...ESPECIALLY ALONG THE SWRN LA GULF CST. STRENGTHENING LOW
TO MID LVL WIND FIELDS ASSOCIATED WITH DEVELOPING SFC WAVE AND
APPROACHING UPR SYSTEM MAY YIELD AN ENVIRONMENT INCREASINGLY
FAVORABLE FOR SLIGHTLY ELEVATED ROTATING STORMS NEAR AND JUST NE OF
SFC WAVE. ATTM IT APPEARS THAT THE MAIN WARM SECTOR WILL REMAIN
LARGELY OFFSHORE...AT LEAST UNTIL VERY LATE IN THE PERIOD.
IF...HOWEVER...DISCRETE STORMS DO INDEED FORM OVER THE CSTL
WATERS...A LOW PROBABILITY THREAT WOULD EXIST FOR A TORNADO OR TWO
ONSHORE AS THE MID LVL JET BACKS/STRENGTHENS ATOP MOIST SSELY
NEAR-SFC FLOW.

..CORFIDI/GRAMS.. 10/26/2009

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