SWODY2
SPC AC 221715
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1115 AM CST TUE DEC 22 2009
VALID 231200Z - 241200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE OZARK PLATEAU
INTO ERN TX AND PORTIONS OF THE LOWER MS VALLEY...
...SYNOPSIS...
PRIMARY FEATURE OF INTEREST DURING THE DAY TWO PERIOD IS FULL
LATITUDE TROUGH WHICH IS FORECAST TO AMPLIFY/INTENSIFY WHILE
PROGRESSING EWD INTO THE CNTRL PART OF THE NATION. WITHIN THIS
BROADER-SCALE REGIME...LEAD VORTICITY MAXIMUM /CURRENTLY DIGGING
SEWD INTO THE LOWER CO VALLEY/ WILL PIVOT NNEWD FROM THE RED RIVER
VALLEY INTO THE MID/LOWER MO VALLEYS IN ADVANCE OF MORE SIGNIFICANT
VORTICITY MAXIMUM/JET STREAK SHIFTING EWD THROUGH OK/TX. INDIVIDUAL
HEIGHT FALL/DYNAMIC FORCING MAXIMA WILL ACCOMPANY THESE UPPER
FEATURES...ONE DEVELOPING FROM ERN KS INTO THE MID MO VALLEY...AND
THE OTHER TRANSLATING ACROSS CNTRL/SRN TX.
AT THE SURFACE...LOW PRESSURE ATTENDANT TO THE LEAD IMPULSE WILL
DEVELOP NNEWD THROUGH ERN KS INTO THE LOWER MO VALLEY IN ADVANCE OF
INTENSIFYING COLD FRONT WHICH WILL BEGIN TO SURGE SEWD/EWD THROUGH
CNTRL/ERN PARTS OF OK/TX...PRIMARILY DURING THE LATTER HALF OF THE
PERIOD. SECONDARY CYCLONE DEVELOPMENT MAY OCCUR ALONG THE COLD
FRONT OVER THE ARKLATEX REGION IN RESPONSE TO APPROACH OF
STRONGER...SECONDARY MID/UPPER-LEVEL VORTICITY MAXIMUM WEDNESDAY
NIGHT.
...OZARK PLATEAU SWD INTO PARTS OF ERN TX AND THE LOWER MS
VALLEY...
22/12Z TX/MEXICO COASTAL RAOBS AND CURRENT GOES SOUNDER DATA
INDICATE THAT MARITIME TROPICAL AIR HAS BEEN SUPPRESSED TO THE
CARIBBEAN WITH GENERALLY MODIFIED CONTINENTAL AIR RETURNING NWD
THROUGH THE GULF BASIN. AS SUCH...EXPECT WARM SECTOR AIR MASS TO
REMAIN MODIFIED CONTINENTAL IN CHARACTER WITH DEWPOINTS RANGING FROM
THE LOWER 50S OVER THE OZARK PLATEAU TO LOWER/MID 60S ALONG THE GULF
COAST. THOUGH NOT WELL OBSERVED BY 22/12Z SOUNDING DATA...LATEST
MODEL GUIDANCE SUGGESTS THAT SEPARATE STEEP LAPSE RATE/EML PLUMES
WILL ACCOMPANY THE TWO IMPULSES MENTIONED ABOVE...WHICH SHOULD SERVE
TO ENHANCE CONVECTIVE INSTABILITY ACROSS SYSTEM WARM SECTOR.
A MIX OF ELEVATED AND SURFACE-BASED TSTMS ARE EXPECTED TO BE ONGOING
AT THE ONSET OF THE PERIOD WEDNESDAY MORNING FROM PARTS OF CNTRL/ERN
OK INTO WRN AR AND ERN TX WITHIN ZONE OF LOW-LEVEL WAA AND DEEPER
ASCENT ASSOCIATED WITH LEAD VORTICITY MAXIMUM. THE PRESENCE OF
MODEST MIDLEVEL LAPSE RATES AND CLOUD BEARING SHEAR WILL BE
SUPPORTIVE OF STRONGER UPDRAFTS CAPABLE OF HAIL AND STRONG WIND
GUSTS.
THEREAFTER...GEOMETRY OF LOW-LEVEL MASS FIELD WILL RESULT IN THE
DEVELOPMENT OF A PRE-FRONTAL CONFLUENCE ZONE...SUPPORTIVE OF
REGENERATIVE TSTM DEVELOPMENT ALONG SAME GENERAL N-S CORRIDOR
WEDNESDAY INTO WEDNESDAY NIGHT. WHILE AIR MASS IS NOT EXPECTED TO
BECOME OVERLY UNSTABLE /I.E. MLCAPE GENERALLY LESS THAN 1000-1500 J
PER KG/...VEERING WIND PROFILES AND A MODERATE DEGREE OF LOW AND
DEEP-LAYER SHEAR SUGGEST THE POTENTIAL FOR EMBEDDED SUPERCELLS
CAPABLE OF HAIL...LOCALLY DAMAGING WINDS AND PERHAPS A COUPLE
TORNADOES.
STORMS ARE EXPECTED TO GROW UPSCALE INTO A QUASI-LINEAR CONVECTIVE
SYSTEM WEDNESDAY NIGHT ALONG COLD FRONT AS STRONG DCVA ASSOCIATED
WITH SECONDARY VORTICITY MAXIMUM OVERSPREADS WEAKLY UNSTABLE WARM
SECTOR. HERE TOO...STRONGER STORMS WILL BE CAPABLE OF DAMAGING
WINDS AND POSSIBLY ISOLATED TORNADOES.
..MEAD.. 12/22/2009
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