SWODY1
SPC AC 270052
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 PM CDT SUN AUG 26 2007
VALID 270100Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN
PLAINS...
..NRN PLAINS...
00Z SFC ANALYSIS PLACES A 998 MB LOW OVER SERN MANITOBA WITH A COLD
FRONT SWWD ACROSS CNTRL ND THEN WWD INTO SCNTRL MT. A PRE-FRONTAL
WIND SHIFT EXISTS JUST AHEAD OF THE FRONT ACROSS NERN-SCNTRL ND.
AHEAD OF THIS FEATURE...THE AIR MASS BECAME STRONGLY TO EXTREMELY
UNSTABLE THIS AFTN OWING TO HOT SFC TEMPERATURES AND MOIST BOUNDARY
LAYER BENEATH MID-TROPOSPHERIC LAPSE RATES IN EXCESS OF 7 C PER KM.
HEATING AND PRE-FRONTAL CONVERGENCE COUPLED WITH WEAK LARGE SCALE
SUPPORT AHEAD OF AN APPROACHING MID-LEVEL SHORTWAVE TROUGH ENTERING
SWRN MANITOBA HAVE CONTRIBUTED TO RAPID TSTM DEVELOPMENT OVER ERN ND
EARLY THIS EVE. SEVERAL CELLS HAVE EXHIBITED SUPERCELL
CHARACTERISTICS AND WILL CONTINUE TO DO SO THIS EVENING GIVEN THE
NEARLY 55 KTS OF BULK SHEAR AVAILABLE. 00Z MVX VWP DERIVED
HODOGRAPH USING A STORM MOTION OF 266/28 GIVES A 0-1KM SRH OF AROUND
185 M2/S2. LCLS WILL BE SUFFICIENTLY LOW FOR A TORNADO THREAT AS
LONG AS THE TSTMS REMAIN DISCRETE. OTHERWISE...LARGE HAIL...A FEW
GREATER THAN GOLFBALL SIZE...AND DAMAGING WINDS WILL BE THE EVENING
THREATS.
ACTIVITY WILL LIKELY DEVELOP AND MOVE NEWD ACROSS NWRN MN AND INTO
NWRN ONTARIO OVERNIGHT AS THE PRIMARY LARGE SCALE ASCENT ASSOCIATED
WITH THE APPROACHING WAVE TRANSLATES IN THAT DIRECTION. TAIL-END
STORMS MAY MOVE INTO AND LINGER ACROSS NCNTRL MN THROUGH LATE
TONIGHT.
..UPR MS VLY...
00Z RAOBS SUGGEST THAT THE LEADING EDGE OF THE STRONG ELEVATED MIXED
LAYER /EML/ RESIDES ACROSS THE ERN DAKOTAS AND THE LWR MO VLY WHERE
H7 TEMPERATURES WERE AOA 13 DEG C. MODELS SUGGEST THAT THE
LOW-LEVEL FLOW WILL VEER TO SWLY IN THE 06-09Z TIME FRAME OVER THE
PLAINS...ENHANCING THE WARM/MOIST ADVECTION PROFILES OVER THE UPR MS
VLY REGION ALONG THE ERN PERIPHERY OF THE EML. AS A RESULT...BANDS
OF ELEVATED TSTMS ARE LIKELY TO FORM ACROSS PORTIONS OF CNTRL/SRN MN
SEWD TOWARD NRN IA AND WRN WI LATER TONIGHT. LAPSE RATES ALOFT AND
ROUGHLY 30-40 KTS OF EFFECTIVE SHEAR WILL BE CONDUCIVE FOR STRONG TO
MARGINALLY SEVERE STORMS WITH HAIL.
.RACY.. 08/27/2007
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