AWUS01 KWNH 131336
FFGMPD
ILZ000-IAZ000-131830-

Mesoscale Precipitation Discussion 1033
NWS Weather Prediction Center College Park MD
935 AM EDT Thu Aug 13 2026

Areas affected...Eastern IA...Northern IL

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

Valid 131330Z - 131830Z

SUMMARY...A cluster of strong-to-severe storms racing east from
central IA may cause areas of flash flooding this morning.

DISCUSSION...Doppler radar and GOES-19 satellite imagery show an
impressive MCC moving east through the heart of IA with a
progressive line of storms heading for eastern IA. Surface
observations show 1-hr rainfall totals topping 1.5" in towns just
south of Des Moines and localized totals approaching 2.0". These
storms have prompted a notable FLASH CREST maximum unit streamflow
response near Des Moines and areas along and south of I-80 in
southwest IA.

The MCC is heading into eastern IA and northern IL where MUCAPE is
500-1,000 J/kg and sfc-6km wind shear is >30 kts. The storms have
been supported by its favorable placement beneath the diffluent
right-entrance region of a strong 250mb jet streak. The MCC has
also been sustained by a SWrly 850mb jet that is currently
surpassing 30 kts just north of the Kansas City metro per RAP
mesoanalysis. This 850mb jet is intersecting the stationary front
located over northern MO and acting as a supportive trigger for
these storms. The RAP forecast shows this LLJ will steadily weaken
heading into late morning, and with less instability present over
northern IL, it is possible these storms lose some of their punch
as they move east.

Despite the potential weakening trend, this MCC is going to remain
a concern for additional redevelopment and the frontal boundary
will also remain a key player in additional storms later on today.
NASA SPoRT-LIS 0-40 cm soil moisture percentiles are ranging
between the 70-90th percentiles in eastern IA and northern, which
are a little more sensitive than soils were in southwest IA this
morning. The progressive storm motions will limit the areal extent
at risk of potential flash flooding, but given 1-hr FFGs in
eastern IA and northern IL in some cases are as low as 1.5", there
is the potential for additional flash flooding given the MCC's
history of producing >1.5" rainfall amounts. Poor drainage areas
and locations along I-80, where there is a greater concentration
of suburban communities and thus more hydrophobic surfaces, are
most prone to possible flash flooding.

Mullinax

ATTN...WFO...DVN...ILX...LOT...

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

LAT...LON 42489015 42458977 42428935 42358895 42188864
41948851 41668835 41258844 40858864 40558906
40508957 40509012 40519057 40539079 40589118
40709150 40809169 41049196 41449217 41909212
42109191 42349156 42429116 42459073

$$
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