SWODY1
SPC AC 291938
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0138 PM CST MON NOV 29 2010
VALID 292000Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ERN TX TO THE CNTRL GULF
COAST...
.CHANGES TO PREV OUTLOOK...
1. ADJUST WRN PERIPHERY OF SLIGHT RISK:
MESOLOW HAS FORMED NEAR TEXARKANA AS OF 18Z WITH A BAND OF
PRE-FRONTAL CONFLUENCE EXTENDING SWWD TO THE UPPER TX COAST. DEEP
MOIST CONVECTION HAS BEEN INCREASING WITHIN THIS ZONE AT
MID-AFTERNOON. 18Z RAOBS SHOW THAT THE CAP WAS WEAKENING AND
BOUNDARY LAYER GRADUALLY DESTABILIZING DOWNSTREAM AMIDST STRONG
LOW-LEVEL SHEAR. EXPECT ACTIVITY TO CONTINUE INCREASING IN NUMBER
AND INTENSITY THROUGH THE NIGHT ALONG/AHEAD OF THE PRE-FRONTAL
TROUGH. THE REMAINDER OF THE FORECAST REASONING REMAINS UNCHANGED
WITH HIGHEST POTENTIAL FOR TORNADOES...A COUPLE POSSIBLY
STRONG...AND DAMAGING WINDS FROM ERN LA INTO MUCH OF MS AND SERN AR.
2. EXPAND 10 PERCENT THUNDERSTORM PROBABILITY FARTHER N IN THE UPPER
MS VALLEY
BAND OF ELEVATED CONVECTION ASSOCIATED WITH A STRONG WARM CONVEYOR
BELT HAS EVOLVED IN ERN IA EARLY THIS AFTERNOON AND WILL MOVE INTO
SRN WI AND NRN IL THROUGH EVENING. SPORADIC THUNDER WILL OCCUR WITH
THIS BAND. TO THE W...OTHER STORMS WERE FORMING ALONG THE PRIMARY
COLD FRONT FROM WRN IA INTO NWRN MO WHERE STEEP LAPSE RATES AND
STRONG LARGE-SCALE FORCING WERE EVIDENT. EXPECT THAT STORMS WILL
CONTINUE INTO CNTRL/NRN IA AND NCNTRL MO THROUGH LATE AFTERNOON
BEFORE DIMINISHING. SMALL HAIL MAY OCCUR WITH THE STRONGER STORMS.
..RACY/MEAD/GARNER.. 11/29/2010
.PREV DISCUSSION... /ISSUED 1016 AM CST MON NOV 29 2010/
...ERN TX INTO THE CNTRL GULF STATES...
LEAD VORTICITY MAXIMUM AND ASSOCIATED 80-90 KT MIDLEVEL JET STREAK
OVER THE CNTRL PLAINS WILL CONTINUE NEWD INTO THE UPPER MS VALLEY BY
THIS EVENING. MEANWHILE...NEXT UPSTREAM IMPULSE/JET STREAK OVER THE
LOWER CO VALLEY/NWRN MEXICO WILL TRANSLATE EWD THROUGH THE SRN
PLAINS TONIGHT. AT THE SURFACE...PRIMARY SURFACE LOW OVER SERN NEB
WILL DEVELOP NNEWD INTO THE UPPER GREAT LAKES IN CONJUNCTION WITH
THE LEAD VORTICITY MAXIMUM. AS THIS OCCURS...TRAILING PACIFIC FRONT
WILL PUSH EWD THROUGH THE OZARK PLATEAU AND LOWER ELEVATIONS OF THE
SRN PLAINS INTO LOWER MS VALLEY. LATEST MODEL GUIDANCE SUGGESTS
THAT A SECONDARY SURFACE LOW MAY DEVELOP FROM THE TX COAST NEWD
THROUGH THE ARKLAMISS INTO THE LOWER OH VALLEY...ALONG OR AHEAD OF
PACIFIC FRONT. FINALLY WARM FRONT...CURRENTLY ANALYZED FROM NERN TX
SEWD TO ALONG THE MS/AL COASTS WILL LIFT NWD THROUGH THE PERIOD.
12Z REGIONAL SOUNDINGS INDICATED A WELL-DEFINED CAP ASSOCIATED WITH
AN EML EXTENDING FROM NRN MEXICO ENEWD THROUGH SHV/LCH. ONGOING
ELEVATED TSTMS /SOME CAPABLE OF HAIL/ APPEAR TO BE LOCATED TO THE N
OF THE STRONGER CAP/EML WITHIN A ZONE OF FOCUSED LOW-LEVEL
MOISTENING/ASCENT ALONG 40-50 KT LLJ AXIS. STRONGER WAA/ISENTROPIC
ASCENT ATTENDANT TO THE LLJ IS EXPECTED TO DEVELOP NWD THROUGH THE
MID MS VALLEY INTO UPPER MIDWEST TODAY IN ADVANCE OF LEAD
IMPULSE...WITH DEVELOPING WARM SECTOR REMAINING BETWEEN UPPER
SYSTEMS THROUGH THE REMAINDER OF THE DIURNAL HEATING CYCLE.
THE WEAK FORCING FOR ASCENT COUPLED WITH THE PRESENCE OF THE
ABOVE-MENTIONED CAP WILL LIKELY DELAY ANY ROBUST SURFACE-BASED TSTM
DEVELOPMENT UNTIL LATER THIS AFTERNOON. BY THIS TIME...CONTINUED
BOUNDARY LAYER MOISTENING/WARMING COUPLED WITH CONVERGENCE ALONG
PACIFIC/WARM FRONTS AND PRE-FRONTAL CONFLUENCE ZONE DEVELOPING OVER
FAR ERN TX WILL INCREASE THE LIKELIHOOD OF TSTM ACTIVITY ROOTED
WITHIN THE BOUNDARY LAYER WHERE MLCAPE WILL APPROACH 500-1000 J/KG.
AS MENTIONED ABOVE...INITIAL LLJ CORE WILL DEVELOP NWD AWAY FROM
REGION TODAY. HOWEVER...THE INTENSIFICATION OF SECONDARY LOW-LEVEL
WIND MAXIMUM IS FORECAST BY MID/LATE AFTERNOON INTO TONIGHT FROM
LA/MS INTO THE TN VALLEY IN ADVANCE OF UPSTREAM IMPULSE TRANSLATING
EWD THROUGH THE SRN PLAINS. THE FORMATION OF THIS FEATURE IN
CONJUNCTION WITH SECONDARY SURFACE LOW TRACKING NEWD THROUGH THE
REGION WILL RESULT IN A CORRIDOR OF ENHANCED LOW-LEVEL SHEAR /I.E.
0-1 KM SRH OF 250-400 M2 PER S2/. WHEN COUPLED WITH 50-65 KT OF
DEEP WSWLY SHEAR AND SUFFICIENT INSTABILITY...SETUP WILL FAVOR THE
DEVELOPMENT OF SUPERCELLS AND BOWING STRUCTURES CAPABLE OF TORNADOES
/POSSIBLY STRONG/... DAMAGING WINDS AND SOME HAIL.
STORMS MAY EVOLVE INTO A QLCS OVERNIGHT AS STRONGER FORCING FOR
ASCENT ASSOCIATED WITH SECONDARY VORTICITY MAXIMUM OVERSPREADS
EWD-SURGING COLD FRONT. KINEMATIC ENVIRONMENT WILL REMAIN QUITE
FAVORABLE FOR EMBEDDED SUPERCELL/LEWP STRUCTURES WITH A CONTINUED
RISK FOR TORNADOES AND DAMAGING WINDS OVER PORTIONS OF MS/AL/SERN
LA.
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