SWOMCD
SPC MCD 270643
WIZ000-IAZ000-MNZ000-270815-
MESOSCALE DISCUSSION 1901
NWS STORM PREDICTION CENTER NORMAN OK
0143 AM CDT MON AUG 27 2007
AREAS AFFECTED...E CNTRL/SE MN...WRN WI...NE IA
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 270643Z - 270815Z
THE NEED FOR A WW IS NOT CURRENTLY ANTICIPATED...BUT TRENDS ARE
BEING MONITORED FOR THE POSSIBILITY OF AN INCREASING SEVERE THREAT.
INITIATION OF NEW CONVECTIVE DEVELOPMENT IS UNDERWAY...IN A NORTH/
SOUTH BAND EXTENDING NEAR/WEST OF MINNEAPOLIS THROUGH THE MASON CITY
IA AREA. THIS APPEARS TO BE IN RESPONSE TO LOWER/MID TROPOSPHERIC
WARM ADVECTION...TO THE SOUTH OF A SHORT WAVE IMPULSE LIFTING INTO
WESTERN ONTARIO...WITHIN THE STRONGER BELT OF POLAR WESTERLIES. AS
MID-LEVEL SHORT WAVE RIDGING BUILDS INTO THE NORTH PLAINS AND UPPER
MISSISSIPPI VALLEY...THE STRONGER FORCING...AND ASSOCIATED
THUNDERSTORM ACTIVITY...IS EXPECTED TO SHIFT EASTWARD THROUGH MUCH
OF WESTERN/CENTRAL WISCONSIN BY 12Z.
RUC GUIDANCE INDICATES THAT STORMS ARE PROBABLY HIGH BASED...IN A
VERY MOIST AIR MASS ABOVE A NEAR SURFACE INVERSION LAYER. LEVELS OF
FREE CONVECTION ARE LIKELY ABOVE 700 MB...BUT LARGE CAPE ON THE
ORDER OF 2000 TO 3000 J/KG IS SUPPORTIVE OF VIGOROUS UPDRAFTS. THIS
COULD BE SUFFICIENT TO SUPPORT SOME MARGINALLY SEVERE HAIL...
DESPITE WEAK CLOUD BEARING LAYER SHEAR. OTHERWISE...AT LEAST BRIEF
LOCALLY HEAVY RAINFALL AND FREQUENT CLOUD TO GROUND LIGHTNING
STRIKES APPEAR POSSIBLE AS STORMS INTENSIFY BETWEEN NOW AND
DAYBREAK.
.KERR.. 08/27/2007
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...GRB...MKX...DVN...DLH...ARX...MPX...DMX...
45279364 45959293 46359117 45998965 44758932 43198958
42599042 42299184 42869292 43509308 44209340 44659357
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