SWODY1
SPC AC 091243
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0643 AM CST MON JAN 09 2012
VALID 091300Z - 101200Z
...THERE IS A SLGT RISK OF SVR TSTMS TODAY OVER THE MIDDLE AND UPPER
TX COAST INTO SWRN LA...
...SYNOPSIS...
MID- AND UPPER-LEVEL LOW CENTERED NEAR OR S OF ELP WILL BEGIN TO
ACCELERATE EWD LATER TODAY IN RESPONSE TO THE APPROACH OF AN
AMPLIFYING UPSTREAM SYSTEM OVER THE PACIFIC NW. AN ASSOCIATED JET
STREAK OVER NRN MEXICO WILL PROGRESS THROUGH BASAL PORTION OF UPPER
LOW...REACHING THE TX COAST INTO SABINE RIVER VALLEY BY TONIGHT. IN
THE LOW LEVELS...A WEAK SURFACE LOW ANALYZED NEAR COT AS OF 12Z WILL
CONCURRENTLY DEVELOP ENEWD NEARLY PARALLEL TO THE TX COAST BEFORE
CURVING NWD/NWWD WHILE OCCLUDING OVER THE SABINE VALLEY. ASSOCIATED
BAROCLINIC ZONE OVER TX WILL LIKELY CONTINUE TO SAG SLOWLY SWD
--AIDED BY CONVECTIVE OUTFLOW-- WHILE REMAINING QUASI-STATIONARY
OVER CNTRL PARTS OF LA...MS AND AL. MEANWHILE...SEGMENT OF BOUNDARY
TRAILING SURFACE LOW WILL ADVANCE MORE RAPIDLY SEWD/SWD AS A COLD
FRONT.
...MID/UPPER TX COAST INTO SWRN LA...
12Z CRP SOUNDING INDICATES THAT LOW-LEVEL AIR MASS HAS MOISTENED
CONSIDERABLY OVERNIGHT WITH DEWPOINTS NOW IN THE UPPER 60S TO AROUND
70 F AND A ML MIXING RATIO OF 14.5 G/KG. GIVEN THE OBSERVED STEEP
MIDLEVEL LAPSE RATES...LOCAL ENVIRONMENT IS ALREADY MODERATELY
UNSTABLE WITH MLCAPE VALUES OF 1000-2000 J/KG. EXPECT WARM SECTOR
TO SHRINK TOWARD THE TX COAST TODAY AS COMPOSITE SURFACE BOUNDARY
ADVANCES SEWD. NONETHELESS...THE STRONGER THAN FORECAST INSTABILITY
WITHIN THE NARROWING WARM SECTOR WILL BE MORE THAN SUFFICIENT TO
SUPPORT EMBEDDED SUPERCELL STRUCTURES GIVEN 40-50 KT OF DEEP-LAYER
SHEAR AND EFFECTIVE SRH OF 100-200 M2/S2. THE GREATEST THREAT FOR A
COUPLE OF TORNADOES...LOCALLY DAMAGING WINDS AND HAIL IS EXPECTED TO
RESIDE FROM THE MID/UPPER TX COAST INTO SWRN LA TODAY.
FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 8.
...LOWER MS VALLEY/CNTRL GULF STATES...
12Z SOUNDINGS OVER THE LOWER MS VALLEY INDICATE THAT ONLY MODEST
DAYTIME HEATING WILL BE REQUIRED TO BOOST MLCAPE VALUES TO AROUND
1000 J/KG WITH LITTLE OR NO REMAINING CIN. WHILE LARGE-SCALE
FORCING FOR ASCENT WILL REMAIN WEAKER THAN THAT OVER TX...PERSISTENT
LOW-LEVEL WAA AND CONVERGENCE ALONG QUASI-STATIONARY BOUNDARY SHOULD
BE SUFFICIENT TO INITIATE WIDELY SCATTERED TSTMS LATER TODAY. GIVEN
THE PRESENCE OF 40-50 KT WLY FLOW IN THE MIDLEVELS...SUFFICIENT
VERTICAL SHEAR WILL EXIST TO SUPPORT ROTATING STORMS CAPABLE OF
LOCALLY DAMAGING WINDS AND PERHAPS SOME HAIL.
..MEAD/BOTHWELL.. 01/09/2012
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