SWODY2
SPC AC 281730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST SUN NOV 28 2010
VALID 291200Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS E TX/LOWER MS VALLEY AND
PART OF CENTRAL GULF COAST...
...SYNOPSIS...
LARGE SCALE TROUGH EVOLVING ACROSS THE WRN HALF OF THE CONUS TODAY
WILL SHIFT EWD MONDAY INTO THE CENTRAL STATES WITH THE TROUGH
EXPANDING/AMPLIFYING SWD OVER TX AS A SHORTWAVE TROUGH DIGS SEWD
TOWARD THIS REGION FROM THE SRN GREAT BASIN. MEANWHILE...A LEAD
SHORTWAVE TROUGH AND ATTENDANT SURFACE LOW WILL TRACK FROM THE
CENTRAL PLAINS TO THE UPPER MS VALLEY THIS FORECAST PERIOD.
AT THE SURFACE...A COLD FRONT TRAILING SWD FROM THE CENTRAL PLAINS
LOW WILL PROGRESS EWD TOWARD THE MID MS VALLEY...WHILE THE SRN
EXTENT SPREADS SEWD THROUGH THE SRN PLAINS. THIS EXPANSIVE COLD
FRONT WILL INITIALLY OVERTAKE A PRE-FRONTAL TROUGH/DRY LINE IN THE
OZARKS REGION BY LATE MONDAY AFTERNOON...AND THEN THE FRONT SHOULD
REACH THE LOWER MS VALLEY AND MOVE OFF THE TX COAST LATER MONDAY
NIGHT. THE SRN EXTENT OF THE DRY LINE WILL SPREAD EWD REACHING ERN
OK/TX BY AROUND NOON MONDAY...AND THEN PROGRESS E TOWARD THE LOWER
MS VALLEY BEFORE BEING OVERTAKEN BY THE COLD FRONT LATE IN THE
PERIOD. BY 12Z TUESDAY...THE COLD FRONT SHOULD EXTEND SSWWD THROUGH
THE LOWER OH/TN VALLEYS...SERN LA TO THE WRN EXTENT OF THE GULF OF
MEXICO. A WARM FRONT IS EXPECTED TO MOVE INLAND ACROSS E TX/LA
DURING THE FIRST HALF OF THE PERIOD...AND THEN ADVANCE INTO CENTRAL
MS/AL MONDAY NIGHT.
...E TX/LOWER MS VALLEY/CENTRAL GULF COAST...
THE SLIGHT RISK AREA FOR DAY 2 /12Z MON-12Z TUE/ HAS BEEN EXPANDED
WWD TO INCLUDE PART OF E TX...AND NWD TO INCLUDE THE REST OF LA...
EXTREME SRN AR AND MORE OF CENTRAL MS/SWRN AL.
SLY LOW LEVEL WINDS AHEAD OF THE DRY LINE WILL SUPPORT CONTINUED
MOISTURE RETURN /SURFACE DEWPOINTS IN THE MID-UPPER 60S/ SPREADING
INLAND WITHIN THE WARM SECTOR OVER E TX AND MUCH OF LA INTO MONDAY
AFTERNOON. DESPITE MODEST MIDLEVEL LAPSE RATES /AROUND 6.5 C PER
KM/...THIS MOISTURE COMBINED WITH SOME SURFACE HEATING SHOULD RESULT
IN MLCAPE VALUES RANGING FROM 500-800 J/KG. ALTHOUGH THIS REGION
WILL BE LOCATED BETWEEN TWO SHORTWAVE TROUGHS WITH LITTLE HEIGHT
FALLS EXPECTED THROUGH 30/00Z...LOW LEVEL CONVERGENCE ALONG THE
ADVANCING DRY LINE AND WARM FRONT ALONG WITH WAA WILL SUPPORT TSTM
DEVELOPMENT. STRENGTHENING SWLY MIDLEVEL WINDS /50+ KT/ THROUGH THE
FORECAST PERIOD AND 30-45 KT SLY LOW LEVEL WINDS WILL RESULT IN
STRONG EFFECTIVE BULK SHEAR /50+ KT/. THE LACK OF STRONGER
MID-UPPER LEVEL FORCING THROUGH 30/00Z SUGGESTS THAT INITIAL STORMS
SHOULD BE FOCUSED MORE SO ALONG THE SURFACE BOUNDARIES...WITH THE
DEGREE OF DEEP LAYER AND LOW LEVEL SHEAR SUPPORTING LINE SEGMENTS
AND SOME SUPERCELLS. MODELS SUGGEST THIS THREAT COULD DEVELOP BY
LATE MONDAY MORNING OVER E TX AND ADJACENT LA WITH THE THREAT FOR
ISOLATED TORNADOES AND DAMAGING WINDS. A THREAT FOR SIGNIFICANT
TORNADOES WILL EXIST ACROSS NRN LA MONDAY AFTERNOON/EARLY EVENING.
WHILE THERE MAY BE A DECREASE IN TSTM COVERAGE/INTENSITY DURING THE
EARLY PART OF MONDAY EVENING...THE ARRIVAL OF STRONGER FORCING FOR
ASCENT/HEIGHT FALLS AHEAD OF THE DIGGING SHORTWAVE TROUGH TOWARD
CENTRAL TX SUGGESTS STORMS SHOULD RAMP UP AGAIN LATE IN THE
EVENING/OVERNIGHT OVER THE LOWER MS VALLEY. THE INLAND INTRUSION OF
THE MOIST WARM SECTOR WILL AID IN SUFFICIENT DESTABILIZATION FOR
SURFACE BASED STORMS INTO THE SRN HALF OF MS AND SWRN AL OVERNIGHT.
FURTHER INCREASE IN MIDLEVEL WINDS ATOP THE LLJ WILL SUPPORT STRONG
DEEP LAYER SHEAR AND INCREASING LOW LEVEL HODOGRAPH CURVATURE FOR A
LATE EVENING AND OVERNIGHT TORNADO THREAT...SOME OF WHICH MAY BE
SIGNIFICANT. A THREAT FOR DAMAGING WINDS WILL ALSO BE POSSIBLE.
..PETERS.. 11/28/2010
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