978
ACUS11 KWNS 182052
SWOMCD
SPC MCD 182051
MIZ000-182245-

Mesoscale Discussion 0471
NWS Storm Prediction Center Norman OK
0351 PM CDT Fri Apr 18 2025

Areas affected...parts of cntrl and srn Lower Michigan

Concerning...Severe potential...Watch possible

Valid 182051Z - 182245Z

Probability of Watch Issuance...40 percent

SUMMARY...The potential for thunderstorm initiation along and just
south of a warm frontal zone across lower Michigan is being
monitored for a possible severe weather watch issuance, as this may
be accompanied by increasing risk for severe hail and wind by 6-8 PM
EDT.

DISCUSSION...A weak perturbation, within larger-scale anticyclonic
flow on the northwestern periphery of prominent mid-level ridging,
will continue to progress across and northeast of the middle
Mississippi Valley through late afternoon.  Associated forcing for
ascent appears to have aided a flare up of convection approaching
the Greater Milwaukee vicinity, and latest Rapid Refresh suggests
that this may contribute to erosion of inhibition associated with
elevated mixed-layer air across southern Lower Michigan by the
22-00Z time frame.

As this occurs, the moistening boundary-layer along and south of a
warm frontal zone (downstream of a weak surface low migrating across
southern Wisconsin/northern Illinois) may become characterized by
CAPE in excess of 1000 J/kg within the next couple hours, in the
presence of strong deep-layer shear.  Although calibrated HREF and
NCEP SREF guidance indicates highest probabilities for thunderstorm
development evolving above/to the north of the warm frontal zone,
initiation of storms closer to and just south of the frontal zone
will provide the highest potential for organizing and intensifying
into a severe hail and wind threat.

..Kerr/Smith.. 04/18/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DTX...IWX...GRR...

LAT...LON   43118598 43578274 42438293 41798653 42558615 43118598

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN