MESO: Mesoscale Discussion 2305

ACUS11 KWNS 082153
SWOMCD
SPC MCD 082153
LAZ000-TXZ000-090000-

MESOSCALE DISCUSSION 2305
NWS STORM PREDICTION CENTER NORMAN OK
0353 PM CST TUE NOV 08 2011

AREAS AFFECTED...SOUTHEAST TEXAS

CONCERNING...TORNADO WATCH 876...

VALID 082153Z - 090000Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 876 CONTINUES.

ISOLATED TORNADO THREAT CONTINUES ACROSS WW 876. THE THREAT IS
LIKELY TO PERSIST FOR AT LEAST THE NEXT 2-3 HRS...WITH A SLOW
DECREASING TREND WITH TIME.

AT 2130Z...A CLUSTER OF SUPERCELLS IS ONGOING ACROSS LIBERTY AND
HARDIN COUNTY...WITH SCATTERED NON-SEVERE CONVECTION ACROSS THE
REMAINDER OF THE WATCH. MODERATE CAPE OF AROUND 1000-1500 J/KG
REMAINS ACROSS THE WATCH AREA PER SFC MESOANALYSIS...WITH SUFFICIENT
EFFECTIVE SHEAR /AROUND 40 KTS/ TO SUPPORT SUPERCELL STRUCTURES. 0-1
KM SHEAR OF 20-25 KTS CONTINUES TO SUPPORT A THREAT OF ISOLATED
TORNADOES...ESPECIALLY ACROSS ERN PARTS OF THE WATCH. THERE IS SOME
THREAT OF SEVERE WIND AS WELL...ESPECIALLY WHERE CELL MERGERS RESULT
IN SMALL BOWING STRUCTURES.

WHILE DEEP-LAYER SHEAR WILL CONTINUE TO SUPPORT OCCASIONAL SUPERCELL
STRUCTURES...LOW-LEVEL SHEAR IS LIKELY TO WEAKEN WITH TIME AS A
MIDLEVEL TROUGH CURRENTLY OVER OKLAHOMA EJECTS ENE AWAY FROM THE
AREA...WITH A DECREASING TORNADO THREAT ACROSS THE WATCH FROM WEST
TO EAST. CURRENT ACTIVITY MAY PERSIST FOR THE NEXT 2-3 HRS BEFORE
COVERAGE BEGINS TO DECREASE. A COLD FRONT MOVING INTO THE WESTERN
PART OF THE WATCH MAY TRIGGER A MORE LINEAR MODE OF CONVECTION WITH
A LOW-END WIND THREAT EARLY THIS EVENING...BUT THIS SCENARIO IS
UNCERTAIN GIVEN WEAKENING UPPER SUPPORT.

..DEAN.. 11/08/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...SHV...HGX...FWD...

LAT...LON 30749609 31229575 31289477 31249399 30819378 30429373
30099390 29939468 29869507 29839553 30059590 30309606
30749609

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