SWODY1
SPC AC 210058
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 PM CDT MON AUG 20 2007
VALID 210100Z - 211200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID MO
VALLEY AND CNTRL PLAINS...
..MID MO VALLEY/CNTRL PLAINS...
A QUASI-LINEAR MCS WITH SEVERAL EMBEDDED STORM CLUSTERS IS ONGOING
FROM SE NEB SWWD ACROSS CNTRL AND SWRN KS ALONG AND AHEAD OF A
FRONTAL BOUNDARY. THE MCS IS LOCATED IN A VERY UNSTABLE AIRMASS WITH
MLCAPE VALUES INDICATED BY OBJECTIVE ANALYSIS IN THE 3000 TO 4500
J/KG RANGE. THE STRONG INSTABILITY SHOULD SUSTAIN SEVERAL STORM
CLUSTERS SEWD INTO ERN KS...NW MO AND ACROSS SRN IA THIS EVENING.
ADDITIONAL DEVELOPMENT MAY TAKE PLACE ACROSS FAR SE SD...SW MN INTO
NW IA AS SUGGESTED BY SEVERAL SHORT-TERM MODELS.
CONCERNING ENVIRONMENTAL WIND FIELDS ACROSS THE SLIGHT RISK
AREA...THE LATEST REGIONAL PROFILERS SHOW SUBSTANTIAL VEERING BELOW
1 KM WITH 35 TO 45 KT OF MID-LEVEL FLOW. THIS IS CREATING MODERATE
VERTICAL SHEAR SUFFICIENT FOR SUPERCELLS ALTHOUGH RECENT TRENDS
SUGGEST MULTICELL LINE SEGMENTS ARE COMMON AS WELL. THE LATEST
WSR-88D VWP FROM OMAHA SHOWS 0-1 KM SHEAR OF 30 KT SUGGESTING AN
ISOLATED TORNADO THREAT SHOULD ALSO EXIST. IN ADDITION...AN ISOLATED
THREAT FOR VERY LARGE HAIL MAY ACCOMPANY THE STRONGEST SUPERCELLS
ESPECIALLY ACROSS ERN NEB WHERE MID-LEVEL TEMPS ARE SLIGHTLY COOLER
WITH 500 MB TEMPS AROUND -7 C. FURTHER SOUTHWEST ACROSS NRN AND
CNTRL KS...A LARGE HAIL THREAT WILL ALSO EXIST DUE TO THE STRONG
INSTABILITY AND STEEP MID-LEVEL LAPSE RATES. WIND DAMAGE WILL ALSO
BE POSSIBLE ESPECIALLY WITH SHORT MULTICELL LINE SEGMENTS AS THE
STORMS MOVE INTO WRN IA...ERN KS...SCNTRL KS AND NW MO THIS EVENING.
..UPPER OH VALLEY...
LATEST SFC ANALYSIS SHOWS AN OUTFLOW BOUNDARY FROM SRN OH EXTENDING
EWD ACROSS WV INTO NRN VA. NUMEROUS THUNDERSTORMS ARE ONGOING NORTH
OF THE BOUNDARY IN A MARGINALLY UNSTABLE ENVIRONMENT WITH OBJECTIVE
ANALYSIS SHOWING SBCAPE VALUES AROUND 1000 J/KG. ALTHOUGH LOW-LEVEL
LAPSE RATES ARE BECOMING LESS STEEP WITH TIME...STRONG LOW-LEVEL
FLOW OF 30 TO 35 KT MAY PROMOTE A POTENTIAL FOR MARGINALLY SEVERE
WIND GUSTS IN WV AND NRN VA OVER THE NEXT 1 TO 3 HOURS. THE THREAT
SHOULD DECREASE AS INSTABILITY AND LOW-LEVEL LAPSE RATES CONTINUE TO
BECOME LESS FAVORABLE EARLY THIS EVENING.
.BROYLES.. 08/21/2007
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