SWODY1
SPC AC 280054
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 PM CDT WED JUL 27 2011
VALID 280100Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...CNTRL PLAINS...UPPER MIDWEST AND SRN GREAT LAKES...
...CNTRL AND NRN PLAINS/MID-MO VALLEY...
A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS ONGOING IN THE BLACK
HILLS LOCATED ALONG AN AXIS OF MODERATE INSTABILITY. MESOANALYSIS
SHOWS MLCAPE VALUES FROM 1500 TO 2500 J/KG IN MUCH OF SD WITH THE
RAPID CITY WSR-88D VWP SHOWING 40 KT OF DEEP LAYER SHEAR. IN
ADDITION...THE 00Z SOUNDING IN RAPID CITY HAS A STEEP MID-LEVEL
LAPSE RATE. THIS ENVIRONMENT WILL CONTINUE TO SUPPORT ORGANIZED
STORMS AND POSSIBLY SUPERCELLS WITH ISOLATED LARGE HAIL. THE
THUNDERSTORMS ONGOING IN WRN SD ARE ORGANIZING INTO A LINE
SUGGESTING A WIND DAMAGE THREAT SHOULD ALSO EXIST AS THE LINE MOVES
EWD INTO CNTRL SD THIS EVENING.
FURTHER TO THE SOUTHEAST ACROSS ERN NEB AND IA...SOME MODEL
FORECASTS INITIATE SCATTERED THUNDERSTORMS THIS EVENING ALONG AN
AXIS OF STRONG INSTABILITY. THE OMAHA 00Z SOUNDING SHOWS AN
IMPRESSIVE ENVIRONMENT WITH MLCAPE VALUES AROUND 4500 J/KG...0-6 KM
SHEAR OF ABOUT 35 KT AND A 700 TO 500 MB LAPSE RATE OF 8.0 C/KM. IF
DISCRETE CELLS CAN INITIATE...THIS ENVIRONMENT SHOULD BE FAVORABLE
FOR SUPERCELLS WITH AN ISOLATED LARGE HAIL THREAT. HOWEVER...IT
REMAINS UNCLEAR WHAT THE DOMINANT STORM MODE WILL BE. IF THE CELLS
QUICKLY ORGANIZE INTO A LINE...THEN WIND DAMAGE COULD BE THE GREATER
THREAT.
...UPPER MS VALLEY/NRN OH VALLEY...
A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS ONGOING ALONG THE
IL-WI STATE-LINE ALONG THE NRN EDGE OF AN AXIS OF STRONG
INSTABILITY. THE STORMS WILL MOVE EWD TOWARD THE CHICAGO AREA THIS
EVENING ALONG A STRONG INSTABILITY GRADIENT. THE 00Z SOUNDING AT
DAVENPORT IA SHOWS MLCAPE OF 4500 J/KG...0-6 KM SHEAR OF 30 KT AN A
CURVED LOW-LEVEL HODOGRAPH. THIS SHOULD BE SUFFICIENT FOR SUPERCELLS
WITH AN ISOLATED TORNADO THREAT ESPECIALLY AS LOW-LEVEL FLOW
STRENGTHENS EARLY THIS EVENING. THE STORMS MAY ALSO PRODUCE WIND
DAMAGE ESPECIALLY IF A LINE-SEGMENT WITH A COLD POOL CAN ORGANIZE.
...CNTRL PLAINS...
SCATTERED STRONG THUNDERSTORMS ARE ONGOING ACROSS THE CNTRL PLAINS
ON THE SRN EDGE MODERATE INSTABILITY. THE ACTIVITY IS LOCATED ON THE
WRN EDGE OF AN UPPER-LEVEL RIDGE. DEEP LAYER SHEAR IS RELATIVELY
WEAK BENEATH THE RIDGE SUGGESTING THE SEVERE THREAT SHOULD BE
ISOLATED AND UNORGANIZED. HOWEVER...STEEP LOW-LEVEL LAPSE RATES AND
LARGE SFC-TEMP DEWPOINT SPREADS MAY BE CONDUCIVE FOR A MARGINAL WIND
DAMAGE THREAT EARLY THIS EVENING.
...INTERMOUNTAIN WEST...
SCATTERED STRONG THUNDERSTORMS ARE ONGOING ACROSS UT AND THIS
ACTIVITY SHOULD SPREAD EWD INTO WRN CO THIS EVENING. MESOANALYSIS
CURRENTLY SHOW MLCAPE VALUES ACROSS UT AND WRN CO AROUND 1000 J/KG
WITH VERY STEEP LAPSE RATES AND ENOUGH VERTICAL SHEAR FOR A MARGINAL
SEVERE THREAT. HAIL AND STRONG GUSTY WINDS MAY ACCOMPANY THE MORE
INTENSE CELLS THIS EVENING.
...CNTRL GULF COAST STATES...
SCATTERED THUNDERSTORMS ARE ONGOING ACROSS THE CNTRL GULF COAST
STATES IN A MODERATE UNSTABLE AIRMASS. THE STRONGEST INSTABILITY IS
LOCATED ACROSS NRN LA AND CNTRL MS SUGGESTING THE WIND DAMAGE THREAT
WILL BE GREATEST IN THE LOWER MS VALLEY EARLY THIS EVENING. WEAK
VERTICAL SHEAR SHOULD KEEP ANY THREAT VERY ISOLATED.
..BROYLES.. 07/28/2011
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