Mesoscale Precipitation Discussion 0644
NWS Weather Prediction Center College Park MD
1245 PM EDT Fri Jul 11 2025

Areas affected...Central and Eastern IA...Northern MO...Northwest
IL...Southwest WI

Concerning...Heavy rainfall...Flash flooding likely

Valid 111645Z - 112245Z

SUMMARY...Expanding clusters of heavy showers and thunderstorms
are expected going through the afternoon hours. Locally moist
antecedent conditions along with high rainfall rates and some
cell-training concerns will foster a likelihood for scattered
areas of flash flooding.

DISCUSSION...The latest GOES-E IR/WV suite shows a strong
shortwave trough over the central Plains gradually advancing into
areas of the Upper Midwest which is fostering the eastward advance
of low pressure along a frontal boundary draped over the region.
Already there are some cooling convective cloud tops noted over
north-central IA as strengthening warm air advection and the
pooling of strong instability occurs ahead of this low center.

A well-defined west to east oriented instability gradient extends
across central and eastern IA through western IL, with MUCAPE
values across the region on the order of 1000 to 2000 J/kg.
However, areas near and south of the front going down into
northern MO show substantially stronger instability fields with
MUCAPE values here of 3000 to 4000 J/kg. Over the next few hours,
stronger shortwave-driven DPVA, along increasing moisture and
instability transport along and north of the boundary should favor
an increase in elevated convection for especially central and
eastern IA, with convective clusters potentially becoming aligned
in a west to east training fashion given their orientation to the
deeper layer steering flow.

However, by mid to late-afternoon, much more surface-based warm
sector convection should initiate and expand in coverage across
southern IA and northern MO ahead of the shortwave energy/low
center, and especially as any remaining low-level CINH is eroded.
Effective bulk shear parameters will be on the order of 30 to 40+
kts, which coupled with strong instability will yield a
substantial mixture of multi-cell and supercell convection.

Modestly anomalous PWs of 1.6 to 1.8 inches are in place, which
coupled with the expected organized nature of the convection
should support rainfall rates reaching easily into the 1.5 to 2.5
inch/hour range. High rainfall rates and some cell-training
concerns along with cell-mergers may yield some localized rainfall
totals of 3 to 5 inches.

The antecedent conditions over portions of central and eastern IA,
northwest IL and southwest WI are relatively moist from recent
rainfall, and this coupled with the additional heavy rains will
likely encourage somewhat more efficient runoff. Scattered areas
of flash flooding are expected, and there will also be locally
notable urban flash flooding concerns. There are drier conditions
noted farther south over southern IA and northern MO which will
temper the flash flood threat here a bit more, but even here, the
high rainfall rates here will promote a well-defined concern for
some flash flooding.

Orrison

ATTN...WFO...ARX...DMX...DVN...EAX...ILX...LOT...LSX...MKX...

ATTN...RFC...KRF...MSR...NWC...

LAT...LON   43449143 43298957 42488904 41638942 40749061
            39609256 39459391 40009432 40559430 40939430
            41389436 42159470 42559456 43119352