MESO: Mesoscale Discussion 0656

ACUS11 KWNS 020348
SWOMCD
SPC MCD 020348
WIZ000-MNZ000-IAZ000-020515-

MESOSCALE DISCUSSION 0656
NWS STORM PREDICTION CENTER NORMAN OK
1048 PM CDT TUE MAY 01 2012

AREAS AFFECTED...PORTIONS SERN MN...WRN WI.

CONCERNING...TORNADO WATCH 223...

VALID 020348Z - 020515Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 223 CONTINUES.

SUMMARY...WW MAY BE CLEARED BEHIND MAIN CONVECTIVE BAND. PRIMARY
SVR THREAT IS FROM DAMAGING GUSTS...WITH ISOLATED HAIL ALSO
EXPECTED. BRIEF TORNADO OR TWO STILL MAY OCCUR FROM EITHER
BOOKEND/BOW VORTICES OR MISOCIRCULATIONS ALONG LEADING EDGE OF QLCS.
OVERALL SVR POTENTIAL SHOULD CONTINUE TO LESSEN WITH EWD EXTENT
ACROSS WW AREA. HOWEVER...SMALL PORTION OF SERN MN AND NERN IA SE
OF WW MAY EXPERIENCE THREAT FOR SVR GUSTS BEFORE MCS NOW ALONG MN/IA
BORDER WEAKENS.

DISCUSSION...EARLIER WARM FRONT HAS BECOME QUASISTATIONARY ACROSS
THIS REGION...AND WAS ANALYZED AT 3Z FROM W-CENTRAL IL NEAR
OTM...MCW AND S-CENTRAL MN SW OF TWIN CITIES. NARROW CORRIDOR OF
N-CENTRAL/NERN IA AND IMMEDIATE MN BORDER REGION W OF FRONT IS
CHARACTERIZED BY MLCAPE 500-1000 J/KG AND EFFECTIVE SHEAR 40-50
KT...BASED ON MODIFIED FCST SOUNDINGS. MCS SHOULD CONTINUE TO MOVE
EWD AROUND 30 KT...WHICH VIA EXTRAPOLATION WOULD MOVE IT EWD OUT OF
WW AROUND 5Z. LOCAL ACCELERATIONS OF COLD POOL CAUSED BY BOWING MAY
HASTEN THAT PROCESS SLIGHTLY. AS THIS OCCURS...WARM SECTOR
EFFECTIVELY WILL SHRINK FROM S-N...AS MN PORTION OF COMPLEX GOES
ATOP FRONTAL SFC THEN PROCEEDS EWD OVER PROGRESSIVELY DEEPER AND
MORE STABLE LAYER OF LOW THETAE. SVR THREAT THEREFORE WILL BE
DISPLACED SWD INTO WW 224 WITH TIME.

..EDWARDS.. 05/02/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...ARX...MPX...DMX...

LAT...LON 43489429 44469393 44789277 45509178 45109116 44149138
43509199 43489429

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