SWODY2
SPC AC 200527
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1227 AM CDT SUN SEP 20 2009
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF ERN KS/WRN MO
INTO NRN TX...
...SYNOPSIS...
INTENSE VORTICITY MAXIMUM DIGGING SSEWD THROUGH THE NRN HIGH PLAINS
WILL BECOME DETACHED FROM THE PRIMARY BELT OF POLAR WESTERLIES...
FORMING A CUT-OFF CIRCULATION OVER THE CNTRL HIGH PLAINS. THE MOST
SIGNIFICANT HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT IS FORECAST
EQUATORWARD OF VORTICITY MAXIMUM...OVER THE CNTRL/SRN ROCKIES INTO
THE ADJACENT HIGH PLAINS. AT THE SURFACE...A STRONG COLD FRONT WILL
ACCOMPANY THE UPPER SYSTEM SEWD...SERVING AS THE PRIMARY FOCUS FOR
STRONG TO SEVERE TSTM DEVELOPMENT MONDAY AFTERNOON AND EVENING OVER
PARTS OF THE CNTRL AND SRN PLAINS.
...MID MO RIVER VALLEY INTO THE SRN PLAINS...
A MOIST...PRE-FRONTAL AIR MASS /I.E. DEWPOINTS IN THE 60S/ WILL BE
OVERSPREAD BY EML PRECEDING VORTICITY MAXIMUM...CONTRIBUTING TO A
MODERATELY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE APPROACHING
1500-2500 J/KG. TSTMS MAY BE ONGOING OR DEVELOP EARLY IN THE PERIOD
ALONG FRONT OVER PORTIONS OF THE MID/LOWER MO VALLEY WHERE CAP WILL
BE WEAKER. SUBSEQUENT STORM FORMATION IS ANTICIPATED THROUGH THE
DAY SWWD ALONG FRONTAL ZONE AS STRONGER FORCING FOR ASCENT SPREADS
SEWD FROM THE CNTRL ROCKIES AND ERODES REMAINING CONVECTIVE
INHIBITION.
MODEL GUIDANCE CONTINUES TO SUGGEST THAT THE STRONGER DEEP-LAYER
WIND FIELDS WILL LAG SURFACE FRONT TO THE NW. HOWEVER...FORECAST
HODOGRAPHS DO INDICATE CONSIDERABLE VEERING OF WINDS WITH HEIGHT
THROUGH THE LOWEST 3-4 KM AGL WITHIN WARM SECTOR. WHEN COUPLED WITH
25-35 KT OF DEEP-LAYER BULK SHEAR...KINEMATIC ENVIRONMENT WILL
SUPPORT ROTATING STORMS. PRIMARY FACTOR LIMITING A MORE SUBSTANTIAL
SUPERCELL THREAT MAY BE ANAFRONTAL AIRFLOW REGIME ASSOCIATED WITH
FAST-MOVING COLD FRONT. A MORE LIKELY SCENARIO IS FOR TSTM CLUSTERS
OR LINE SEGMENTS TO FORM ALONG SURFACE FRONT WITH THE MAIN SEVERE
THREATS BEING DAMAGING WINDS AND HAIL.
...SRN HIGH PLAINS...
THE COMBINATION OF COLD FRONT...OROGRAPHIC UPSLOPE AND INCREASING
DEEP ASCENT AHEAD OF VORTICITY MAXIMUM MAY SUPPORT ISOLATED TO
SCATTERED STORMS ALONG OR PERHAPS IN WAKE OF SURFACE BOUNDARY MONDAY
AFTERNOON INTO EVENING. REGION WILL RESIDE ALONG THE WRN EXTENSION
OF LOW-LEVEL INSTABILITY AXIS...CHARACTERIZED BY STEEP LAPSE RATES
AND MODESTLY STRONG UNIDIRECTIONAL SHEAR. AS SUCH...SETUP MAY FAVOR
THE DEVELOPMENT OF A FEW STRONG TO MARGINALLY SEVERE STORMS CAPABLE
OF LOCALLY STRONG WIND GUSTS AND HAIL.
..MEAD.. 09/20/2009
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