Mesoscale Precipitation Discussion 1058
NWS Weather Prediction Center College Park MD
103 AM EDT Sat Aug 15 2026

Areas affected...Far Northeast KS...Extreme Southeast
NE...Southern IA...Northern MO...Central IL

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

Valid 150503Z - 151100Z

SUMMARY...Developing and expanding areas of heavy showers and
thunderstorms with significant cell-training concerns will exist
overnight. Numerous areas of flash flooding are likely with
elevated concerns for high-end and life-threatening impacts.

DISCUSSION...The latest GOES-E Proxy Visible satellite imagery
shows a well-defined MCV advancing east across central IA which is
in close proximity to a strong elevated instability gradient
situated along and north of a quasi-stationary front draped from
northeast KS through northern MO and into south-central IL.

MUCAPE values of 2000 to 3000 J/kg are in place, with extremely
high PWs of 2.2 to 2.4+ inches based on the latest RAP analysis
and GPS-derived DATA. The 00Z RAOB data from KDVN and KILX show
deep WCL profiles with a highly tropical airmass extending deep
through the vertical column.

This environment is supportive of extreme rainfall rate potential
(2 to 4 inches/hour) over the next several hours as developing and
expanding areas of showers and thunderstorms occur along and north
of the stationary front. This will be facilitated by a
strengthening southwest low-level jet of 30 to 40+ kts overrunning
the front, promoting enhanced isentropic ascent/forcing, and also
driving enhanced moisture and instability transport into the
southern flank of the MCV crossing through the Midwest.

Very high FFG exceedance probabilities are showing up in the 00Z
HREF, and an analysis of the HRRR-TLE data (last 6 runs) strongly
supports a threat for extremely heavy rainfall totals at least
locally across parts of northern MO, southern IA and through
central IL with elevated concerns for high-end impacts.

Current radar and satellite trends integrated with the hires CAMs
suggest potential for as much as 4 to 7+ inches of rain by dawn on
at least a localized basis where enhanced cell-training takes
place. The environment is highly conducive for this, and with such
high moisture and instability profiles coupling with a belt of
stronger mid-level flow/shear for cell-organization/MCS
development, high-end rainfall rates/storm potential appears
likely.

The antecedent conditions are quite sensitive/moist across
especially areas of southeast IA and central IL due to recent
heavy rainfall, and the FFG values are already low here.
Therefore, the expectation over the next several hours will be for
numerous areas of flash flooding to materialize, with concerns for
dangerous and life-threatening impacts.

The threat will be somewhat lower farther back to the
west-southwest across northwest MO, northeast KS and far southeast
NE, but areas of heavy rainfall and potential flash flooding will
exist here too. This situation more broadly over the Midwest needs
to be very carefully monitored going through the early morning
hours.

Orrison

ATTN...WFO...DMX...DVN...EAX...ILX...IND...LOT...LSX...OAX...
TOP...

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

LAT...LON 41659034 41558913 41168760 40328728 39818815
39539102 39409352 39089557 39229639 39759676
40239667 40659585 41279397 41529243