SWODY2
SPC AC 211723
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CDT TUE SEP 21 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN/CNTRL PLAINS
INTO THE MID/UPPER MS VALLEY...
...NRN/CNTRL PLAINS TO MID/UPPER MS VALLEY...
WRN U.S. TROUGH WILL TRANSLATE INTO THE CNTRL ROCKIES LATE IN THE
PERIOD...THOUGH SEVERAL EMBEDDED SHORTWAVES WILL EJECT NEWD INTO THE
CNTRL PLAINS AHEAD OF THE PRIMARY TROUGH AXIS. THESE LEAD IMPULSES
WILL LIKELY ENHANCE THE THREAT FOR CONVECTION EARLY IN THE PERIOD AS
LOW LEVEL WARM ADVECTION INTENSIFIES NORTH OF RETREATING WARM FRONT.
IT APPEARS THUNDERSTORMS WILL BE ONGOING AT THE START OF THE PERIOD
ALONG NOSE OF INCREASING LLJ OVER WRN NEB INTO PORTIONS OF SCNTRL
SD. THIS ACTIVITY SHOULD SEE MARKED GROWTH/EXPANSION AS IT SPREADS
NEWD ATOP COOLER BOUNDARY LAYER INTO CNTRL MN DURING THE AFTERNOON
HOURS. FORECAST SOUNDINGS SUGGEST STEEP MID LEVEL LAPSE RATES WILL
ENHANCE INSTABILITY FOR PARCELS LIFTED ABOVE 850MB AND STRONG/SEVERE
ELEVATED THUNDERSTORM CLUSTERS ARE POSSIBLE WITH THIS LEADING
ACTIVITY. THE PRIMARY SEVERE THREAT WILL BE LARGE HAIL WITH COOL
SECTOR STORMS.
LATER IN THE DAY IT APPEARS STRONG HEATING ACROSS THE HIGH PLAINS
WILL AID SFC-BASED CONVECTION ALONG LEE TROUGH FROM ERN CO INTO WRN
NEB. INHIBITION WILL WEAKEN AS TEMPERATURE READINGS WARM INTO THE
MID-UPPER 80S WITHIN INCREASINGLY SHEARED ENVIRONMENT. ALTHOUGH
SFC-6KM SHEAR IS NOT EXPECTED TO BE REAL STRONG...ON THE ORDER OF
30KT...VEERING PROFILES WITH HEIGHT SUGGEST INITIAL ACTIVITY VERY
WELL COULD ROTATE AND SUPERCELLS ARE POSSIBLE. ANOTHER ROUND OF
CONCENTRATED THUNDERSTORM ACTIVITY SHOULD EVOLVE ACROSS THE CNTRL
HIGH PLAINS INTO SD AS STRONG FORCING AHEAD OF THE PRIMARY UPPER
TROUGH SPREADS INTO THIS REGION LATE IN THE PERIOD. LARGE HAIL
SHOULD BE THE MAIN SEVERE THREAT WITH THIS ACTIVITY AS WELL...THOUGH
DAMAGING WINDS COULD ACCOMPANY THE STRONGEST STORMS.
...OH VALLEY...
STRONG BOUNDARY LAYER HEATING WILL DEVELOP ALONG/SOUTH OF A WEAK
WIND SHIFT THAT WILL ORIENT ITSELF FROM CNTRL PA...WSWWD INTO OH.
MODELS SUGGEST THE SRN END OF A WEAK SHORTWAVE TROUGH WILL CLIP THIS
PORTION OF THE FRONTAL ZONE...THOUGH HEIGHTS ARE EXPECTED TO
GRADUALLY RISE ACROSS THIS REGION DURING THE DAY. AS A
RESULT...DIURNAL HEATING WILL PROVE INSTRUMENTAL IN CONVECTIVE
DEVELOPMENT ALONG WEAKLY CONVERGENT SFC BOUNDARY WITHIN MODEST WSWLY
FLOW REGIME. IT APPEARS SOME ORGANIZATION IS POSSIBLE WITH THIS
ACTIVITY AND IF LINE SEGMENTS CAN EVOLVE THEN DAMAGING WINDS WILL
BECOME MORE LIKELY. WILL HOLD OFF INCREASING PROBS ACROSS THIS
REGION BUT A SLIGHT RISK MAY NEED TO BE ADDED TO ACCOUNT FOR A
DAMAGING WIND THREAT WITH AFTERNOON CONVECTION.
..DARROW.. 09/21/2010
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