SWODY2
SPC AC 181715
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM CDT TUE MAY 18 2010
VALID 191200Z - 201200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF CNTRL AND SRN OK
INTO NRN TX...
...THERE IS A SLGT RISK OF SVR TSTMS FROM SWRN KS EWD THROUGH MUCH
OF OK AND N TX INTO WRN AR AND NWRN LA...
...SYNOPSIS...
A LARGE-AMPLITUDE...SPLIT FLOW PATTERN WILL CONTINUE THROUGH THE DAY
TWO PERIOD WITH THE PRIMARY FEATURE OF INTEREST BEING A MIDLEVEL
TROUGH WHICH WILL PROGRESS FROM THE CNTRL/SRN ROCKIES EWD INTO THE
CNTRL/SRN PLAINS. THIS SYSTEM WILL BE ATTENDED BY MID AND
HIGH-LEVEL JET STREAKS WHICH WILL PROPAGATE INTO THE RED RIVER
VALLEY...ALONG THE SRN PERIPHERY OF THE PRIMARY VORTICITY MAXIMUM.
IN THE LOW LEVELS...THE EWD PROGRESSION OF THE UPPER-LEVEL SYSTEM
WILL SUPPORT THE SEWD DEVELOPMENT OF A SURFACE LOW FROM SWRN KS INTO
SWRN OK OR NWRN TX BY WEDNESDAY EVENING. MEANWHILE...A WARM FRONT
INITIALLY FROM THE SURFACE LOW SEWD THROUGH THE RED RIVER VALLEY
INTO SRN MS WILL RETREAT NWD THROUGH THE DAY. A DRY LINE WILL
DIURNALLY SHARPEN FROM THE INTERSECTION OF THE RETREATING WARM FRONT
OVER WRN OK SWD INTO THE NWRN/W-CNTRL TX.
...SRN PLAINS INTO ARKLATEX...
CLUSTERS OF ELEVATED TSTMS /SOME CAPABLE OF SEVERE HAIL/ ARE
EXPECTED TO BE ONGOING WEDNESDAY MORNING FROM SWRN KS SEWD INTO
OK...TO THE N OF SURFACE WARM FRONT AND WITHIN 40+ KT LLJ AXIS WHERE
WARM THERMAL AND MOISTURE ADVECTIONS WILL CONTRIBUTE TO MUCAPE
APPROACHING 1000-1500 J/KG. THIS ACTIVITY MAY PERSIST THROUGH THE
DAY OWING TO CONTINUED ISENTROPIC ASCENT OVER LOW-LEVEL BAROCLINIC
ZONE. GIVEN THE POTENTIAL FOR ASSOCIATED STORM COLD POOLS TO
REINFORCE SURFACE RIDGING...THERE IS SOME QUESTION AS TO HOW FAR N
THE WARM FRONT WILL DEVELOP THROUGH THE DAYLIGHT HOURS.
BOUNDARY LAYER DEW POINTS IN THE MID 60S COUPLED WITH MODESTLY STEEP
MIDLEVEL LAPSE RATES ARE EXPECTED TO CONTRIBUTE TO A MODERATE TO
STRONGLY UNSTABLE AIR MASS BY AFTERNOON TO THE S OF THE WARM FRONT
AND E OF DRY LINE WHERE MLCAPE WILL APPROACH 2000-3000 J/KG.
HERE...SUSTAINED CONVERGENCE ALONG THESE BOUNDARIES IN CONJUNCTION
WITH THE INCREASING INFLUENCE OF THE MIDLEVEL SYSTEM SHOULD FOSTER
SCATTERED...SURFACE-BASED TSTMS BY MID/LATE AFTERNOON FROM PARTS OF
WRN AND CNTRL OK INTO N TX.
THE EWD MIGRATION OF THE ABOVE-MENTIONED MID AND HIGH-LEVEL JET
STREAKS WILL RESULT IN SUFFICIENTLY STRONG DEEP-LAYER SHEAR FOR
SUPERCELLS CAPABLE OF VERY LARGE HAIL. 12Z MODEL GUIDANCE SUGGESTS
THAT THE AREA GENERALLY ALONG AND E OF THE I-35 CORRIDOR WILL
MAINTAIN THE STRONGEST LOW-LEVEL SHEAR LATE WEDNESDAY AFTERNOON INTO
WEDNESDAY NIGHT...ALONG THE MIGRATORY LLJ AXIS. HERE...THE GREATEST
TORNADO THREAT WILL EXIST...ESPECIALLY WITH ANY SUPERCELLS THAT CAN
FAVORABLY INTERACT WITH THE RETREATING WARM FRONT.
WHILE VERTICAL SHEAR WILL TEND TO DECREASE WITH SEWD EXTENT ALONG
THE WARM FRONT...THE PRESENCE OF A MOIST AND MODERATELY UNSTABLE AIR
MASS SUGGESTS THE THREAT FOR A FEW SEVERE STORMS FROM THE ARKLATEX
INTO NRN LA.
...ERN NC...
A MOIST LOW-LEVEL AIR MASS COUPLED WITH COOLING ATTENDANT TO AN
EWD-MOVING MIDLEVEL TROUGH WILL RESULT IN A NARROW CORRIDOR OF
MODERATE INSTABILITY AHEAD OF SURFACE LOW AND ASSOCIATED COLD FRONT.
IT APPEARS THAT THE STRONGEST VERTICAL SHEAR WILL REMAIN TO THE N OF
THIS INSTABILITY AXIS THROUGH THE DIURNAL HEATING CYCLE.
HOWEVER...THE PRESENCE OF AROUND 40 KT WSWLY MIDLEVEL FLOW SHOULD BE
SUFFICIENT TO SUPPORT A FEW STRONGER STORMS CAPABLE OF LOCALLY
STRONG WIND GUSTS.
..MEAD.. 05/18/2010
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