Mesoscale Precipitation Discussion 0755
NWS Weather Prediction Center College Park MD
843 AM EDT Sat Jul 19 2025

Areas affected...southeastern Iowa into much of Illinois

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

Valid 191243Z - 191843Z

Summary...A mature convective complex is fostering areas/spots of
1-2 inch/hr rain rates.  It should continue to do so while
traversing areas of Iowa and Illinois this morning, prompting an
isolated to scattered flash flood risk.

Discussion...A mature MCS was propagating southeastward across
central/east-central Iowa as of 12Z this morning.  Out ahead of
this complex, scattered thunderstorms were maintaining their
intensity due to convergence on the nose of 20-30 knot westerly
850mb flow across Iowa and northern Missouri.  A few of these
storms were merging into the main MCS over east-central Iowa,
prompting prolonged rainfall and hourly rates exceeding 1.5
inches. The environment supporting these storms was abundantly
moist and unstable (characterized by 2+ inch PW values and ~2000
J/kg MLCAPE), supporting efficient rainfall processes beneath the
storms.  This activity should continue southeastward while
supporting occasional mergers and spots of 1.5+ inch/hr rain rates
that exceed local FFG on occasion.  Isolated to scattered areas of
flash flooding are expected throughout the discussion area through
at least 16Z today.

Thereafter, some uncertainty exists with respect to persistence of
the main MCS currently over Iowa.  Low-level shear should weaken
some across the discussion area through mid-morning, and although
current activity appears to be well positioned to leverage
abundant moisture/instability, slightly more stable air exists
downstream across Indiana.  The eastward progression of this
complex may depend on downstream destabilization and any tendency
for cells across Illinois to grow upscale and/or persist within
the better moisture/instability combo.  Regardless of specific
convective evolution, the overall scenario supports isolated to
scattered instances of flash flooding through 18Z - especially
where mergers/training promote rain rates exceeding 1.5 inch/hr.

Cook

ATTN...WFO...DMX...DVN...EAX...ILX...IND...LOT...LSX...PAH...

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

LAT...LON   42449056 41478828 40098691 38878689 38078778
            38329003 39779149 41109313 42319247