SWODY1
SPC AC 081956
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0156 PM CST TUE NOV 08 2011
VALID 082000Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS E TX NEWD INTO SE MO/SW IL...
TWO CHANGES HAVE BEEN MADE TO THE EXISTING OUTLOOK.
1) ADDED 5 PERCENT TORNADO PROBABILITIES ACROSS SERN TX AND INTO A
LARGER PORTION OF WRN LA. STRONGER LOW LEVEL SHEAR WITHIN A
MOIST/UNSTABLE LOW LEVEL ENVIRONMENT...ACCORDING TO THE 18Z SHV RAOB
AND AREA 88D VAD DATA...HAS SUPPORTED STORM-SCALE ROTATION AND
SUPERCELL DEVELOPMENT ACROSS SERN TX WITHIN THE PAST HR. RUC
FORECAST SOUNDINGS AT LEAST LEND CREDENCE TO A CONTINUATION OF THIS
THREAT AS SEMI-DISCRETE STORMS EVENTUALLY MOVE EWD TOWARDS THE
SABINE RIVER. PLEASE REFERENCE LATEST MCD/S AND WATCHES FOR SHORT
TERM DETAILS.
2) HAVE TRIMMED THE WRN EDGE OF THE SLIGHT RISK TO ACCOUNT FOR THE
EWD PROGRESSION OF THE COLD FRONT AND LINEARLY ORIENTED STORM
CLUSTER ACROSS THE ARKLATEX.
..SMITH/DARROW.. 11/08/2011
.PREV DISCUSSION... /ISSUED 1002 AM CST TUE NOV 08 2011/
...E TX/SE OK TO AR/SRN MO THROUGH TONIGHT...
A MIDLEVEL SHORTWAVE TROUGH OVER THE TX PANHANDLE WILL EJECT NEWD TO
THE MID MS VALLEY...WHILE AN ASSOCIATED SURFACE LOW DEVELOPS NEWD
FROM NE OK TO NRN IL ALONG A PRE-EXISTING FRONT. E-S OF THE SURFACE
LOW AND AHEAD OF THE TRAILING COLD FRONT...A MOIST BOUNDARY LAYER
WITH DEWPOINTS OF 64-70 F WILL CONTINUE TO SPREAD NWD FROM E TX/LA
INTO AR. REGIONAL 12Z SOUNDINGS REVEALED A REMNANT ELEVATED MIXED
LAYER OVER CENTRAL TX...WHICH IS CONTRIBUTING TO MLCAPE VALUES OF
500-1000 J/KG AS FAR N AS SE OK...AND 1500-2000 J/KG CLOSER TO THE
MIDDLE/UPPER TX COAST. VISIBLE IMAGERY SHOWS WIDESPREAD CLOUD COVER
IN THE WARM SECTOR NEAR/N OF I-20...AND SOME BREAKS FARTHER S INTO S
CENTRAL/SE TX WHERE SURFACE HEATING WILL BE STRONGER THIS AFTERNOON.
WIDESPREAD CONVECTION IS ONGOING ACROSS SE OK WHERE ISOLATED
DAMAGING GUSTS WERE RECORDED BY THE OK MESONET THIS MORNING...BUT
THE STORMS APPEAR TO HAVE WEAKENED SINCE 15Z. THE THICK CLOUDS
DOWNSTREAM FROM THE ONGOING STORMS CAST DOUBT ON THE DEGREE OF
DESTABILIZATION THIS AFTERNOON INTO W/NW AR...WHILE POTENTIAL FOR
DESTABILIZATION IS A LITTLE GREATER INTO NE TX/SW AR. EXPECT NEW
STORMS TO FORM ALONG AND E OF THE COLD FRONT IN TX THIS
AFTERNOON...SOME OF WHICH COULD BECOME SUPERCELLS GIVEN THE MODERATE
INSTABILITY AND EFFECTIVE BULK SHEAR OF 40-50 KT. ISOLATED DAMAGING
WINDS WILL BE THE MAIN SEVERE STORM CONCERN THIS
AFTERNOON/EVENING...THOUGH A COUPLE OF TORNADOES WILL ALSO BE
POSSIBLE GIVEN THE MOIST ENVIRONMENT WITH EFFECTIVE SRH OF 200-400
M2/S2.
THE STRONGER LOW-LEVEL SHEAR WILL TEND TO DEVELOP NEWD FROM TX INTO
AR/MO BY THIS EVENING WITH THE SURFACE LOW...IN THE AREA OF WEAKER
SURFACE-BASED INSTABILITY. WIND PROFILES WILL REMAIN FAVORABLE FOR
ROTATING STORMS THROUGH TONIGHT NEAR THE PATH OF THE SURFACE LOW
INTO MO/IL...THOUGH THE WIND/TORNADO THREAT WILL BE OFFSET BY ONLY
WEAK SURFACE-BASED INSTABILITY.
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