MESO: Mesoscale Discussion 1462

ACUS11 KWNS 132302
SWOMCD
SPC MCD 132302
WIZ000-MNZ000-IAZ000-140030-

MESOSCALE DISCUSSION 1462
NWS STORM PREDICTION CENTER NORMAN OK
0602 PM CDT FRI JUL 13 2012

AREAS AFFECTED...FAR EAST CENTRAL/SERN AND SRN MN...WEST CENTRAL
WI...AND NRN IA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 132302Z - 140030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE
THROUGH THE EARLY EVENING ACROSS FAR EAST CENTRAL MN/WEST CENTRAL WI
AND SWWD THROUGH SERN MN TO NRN IA. GIVEN RADAR TRENDS AND
AVAILABLE DOWNSTREAM INSTABILITY...IT APPEARS THAT THIS ACTIVITY IS
AT ITS PEAK...THOUGH ISOLATED HAIL APPROACHING SEVERE AND STRONGER
WIND GUSTS WILL BE POSSIBLE.

DISCUSSION...WATER VAPOR IMAGERY SHOWED A TROUGH MOVING SLOWLY EWD
THROUGH THE UPPER MS VALLEY WITH AN EMBEDDED VORTICITY CENTER
LOCATED OVER CENTRAL MN /NEAR 35 SW BRD/. STRONGEST MIDLEVEL FLOW
ATTENDANT TO THIS SYSTEM EXTENDED FROM ERN SD INTO NRN IA. TRENDS IN
REGIONAL RADAR IMAGERY SHOWED A BROKEN LINE OF STORMS EXTENDING FROM
50 S DLH THROUGH THE ERN AND SRN TWIN CITIES METRO TO PARTS OF SOUTH
CENTRAL MN...WITH A SECOND AREA OF STORMS MOVING SEWD INTO NWRN IA.

THE AIR MASS INVOF AND E-S OF THIS ACTIVITY IS MODERATELY UNSTABLE.
THIS COMBINED WITH ASCENT ATTENDANT TO THE TROUGH AND VORTICITY
CENTER WILL CONTINUE TO PROMOTE NEW TSTM DEVELOPMENT AS THE
CONVECTIVE OUTFLOW BOUNDARY ADVANCES EWD INTO NWRN-WRN WI...SERN MN
AND SWD INTO NRN IA. THUS FAR...MOST OF THE STORM REPORTS HAVE BEEN
SUB-SEVERE...AND THIS IS LIKELY DUE TO WEAK DEEP LAYER SHEAR AND
WEAK MIDLEVEL LAPSE RATES LIMITING THE SUSTENANCE OF THIS ACTIVITY.
ALTHOUGH MODELS SUGGEST STORMS WILL PROGRESS EWD INTO WI AND SWD
INTO IA THROUGH THE EVENING...STORMS SHOULD BE IN THEIR PEAK
INTENSITIES FOR AT MOST ANOTHER 1-2 HOURS PRIOR TO BOUNDARY LAYER
STABILIZATION WITH LOSS OF DAYTIME HEATING. MEANWHILE...STORMS THAT
DEVELOP OVER SWRN MN INTO NWRN IA WILL HAVE A GREATER POTENTIAL FOR
ORGANIZATION...GIVEN THE PROXIMITY TO STRONGER DEEP LAYER SHEAR.
HOWEVER...THE PRESENCE OF WEAKER FORCING ALOFT SHOULD LIMIT STORM
COVERAGE INTO NRN IA.

..PETERS/THOMPSON.. 07/13/2012

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

ATTN...WFO...DLH...ARX...MPX...DMX...FSD...

LAT...LON 43519507 44299372 45219308 45849303 46029201 45879125
45129124 43839181 42969314 42889478 43139529 43519507

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