Saturday, November 26, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 260527
SWODY1
SPC AC 260525

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1125 PM CST FRI NOV 25 2011

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE LOWER MS VALLEY...

...LOWER MS VALLEY...

LATEST SHORT RANGE MODEL GUIDANCE IS A BIT MORE AGGRESSIVE IN THE
PROGRESSION OF PLAINS UPPER TROUGH AS IT DIGS TOWARD THE ARKLATEX
AND FORMS A CLOSED CIRCULATION BY THE END OF THE PERIOD. THIS
EVOLUTION IS SUPPORTED BY STRENGTHENING MID LEVEL FLOW ON THE BACK
SIDE OF TROUGH OVER THE CNTRL ROCKIES WHICH SHOULD DRIVE SEWD INTO
TX LATE IN THE PERIOD. NET RESULT WILL BE FOR A SHARPENING FRONTAL
ZONE ACROSS WRN AR/ERN TX BY 18Z BEFORE SURGING ACROSS THE LOWER MS
VALLEY DURING THE OVERNIGHT HOURS. EARLIER THOUGHTS WERE
MOISTURE/INSTABILITY WOULD BE A BIT MEAGER TO SUPPORT ORGANIZED
SEVERE THUNDERSTORMS. HOWEVER 00Z GUIDANCE SUGGESTS SUFFICIENT
BOUNDARY LAYER MOISTENING WILL OCCUR AHEAD OF THE COLD FRONT SUCH
THAT SFC-BASED INSTABILITY WILL EASILY BE ATTAINED ALONG/AHEAD OF
COLD FRONT...POSSIBLY AS EARLY AS 17-18Z. GIVEN THAT DEEP LAYER
SHEAR WILL EASILY SUPPORT ORGANIZED ROTATING UPDRAFTS...IT APPEARS
THE THREAT FOR EMBEDDED SUPERCELLS ALONG A FORCED FRONTAL SQUALL
LINE WILL BE POSSIBLE. LATEST THINKING IS DAMAGING WINDS WILL BE
THE PRIMARY SEVERE THREAT DUE TO THE EXPECTED LINEAR STRUCTURE.
EVEN SO STRONG LOW LEVEL SHEAR AND LOW LCL HEIGHTS FAVOR AT LEAST A
THREAT FOR ISOLATED TORNADOES. PROGRESSION OF ORGANIZED SEVERE
SHOULD BE LIMITED BY WEAKER BUOYANCY OVER ERN MS/SWRN AL.

..DARROW/SMITH.. 11/26/2011

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