Mesoscale Precipitation Discussion 0349
NWS Weather Prediction Center College Park MD
200 PM EDT Mon Jun 13 2022

Areas affected...Eastern Wisconsin...Northern Illinois...Southern
Michigan

Concerning...Heavy rainfall...Flash flooding possible

Valid 1PM CDT to 6PM CDT

SUMMARY...Ongoing complex of thunderstorms to bring torrential
rainfall rates to parts of the Lower Great Lakes this afternoon.
Areas of flash flooding are possible.

DISCUSSION...17Z surface analysis continued to show a surface warm
front inching north through the Midwest with increasingly unstable
atmospheric profiles within the warm sector. Dew points are
reaching the low 80s in parts of southern Illinois and 850mb
moisture flux is increasing along and north of the front. The
ongoing complex of thunderstorms associated with an MCV tracking
into central Wisconsin will continue on an ESE trajectory this
afternoon with convection forming along the strengthening MUCAPE
gradient. MUCAPE will vary significantly by location, but range
generally between 2,000-4,000 J/kg. PWs are also on the rise with
values approaching 2.0" later this afternoon.

RAP mesoanalysis and short term forecasts suggest effective bulk
vertical wind shear will increase to 50-60 knots and effective SRH
values from 100-200 m2/s2 this afternoon. These values are very
favorable for keeping ongoing convection organized. As low level
inflow intersects the front, additional strengthening of the
convection is possible, along with the potential for intensifying
convection on the southwest flank of the complex. Some areas,
notably north of Milwaukee, in southwest Michigan, and northern
Indiana have dealt with measurable rainfall over the last week.
Soils are closer to normal saturation-wise, but they still have
picked up 200-400% of normal rainfall over the last week.

Given rainfall rates with the previous convective cluster in
Minnesota had already produced >2"/hr rates, and the atmosphere
contains similar favorable parameters, the expectation is for max
hourly rainfall rates to range between 2-3"/hr. Areas most
susceptible to flash flooding are the areas that contain more
sensitive soils from rainfall over the past week, as well as
urbanized centers and poor drainage locations. FFGs in these areas
are as low as 1-1.5"/hr, which does include areas between
Milwaukee and Green Bay.