AWUS01 KWNH 271447
FFGMPD
INZ000-ILZ000-MOZ000-272045-

Mesoscale Precipitation Discussion 0139
NWS Weather Prediction Center College Park MD
1046 AM EDT Mon Apr 27 2026

Areas affected...Central Illinois through Greater St. Louis into Indiana

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

Valid 271445Z - 272045Z

SUMMARY...Flash flooding threat continues to progress east across
Illinois through midday with a risk for training thunderstorms
that produce 1 to 2 inch/hour rainfall rates. Rainfall totals of 2
to 3 inches with isolated heavier totals are possible through the
afternoon, with a threat for locally significant urban flash
flooding impacts.

DISCUSSION...A well-defined bowing line of thunderstorms with
areas with rates up to 1.5"/hr is pushing into central Illinois
with a tail extending to west-central Missouri. This is generally
north of the St. Louis metropolitan area, but impacts will
eventually reach there today. Scattered prefrontal activity from
central to southern Illinois will also continue to develop and
shift northeast.

The activity is ahead of a shortwave trough over central KS with
excellent divergence aloft working in tandem with a southwesterly
low-level jet of 45 to 55 kts ahead of the surface low center near
the KS/MO border. Enhanced moisture and instability continues to
flow across southern MO and IL.

MUCAPE values of 2000 to 3000 J/kg with PW around 1.5 inches
across up the mid-Miss Valley. This favorable thermodynamic
environment coupled with enhanced kinematic wind fields/shear will
strongly support a continuation of organized MCS activity across
central IL with the right tail laying down near I-70/St. Louis.

Rainfall rates will remain in the 1 to 2 inch/hour range with
localized additional rainfall totals of 2 to 3 inches. The
progression of the system has recluded further flash flood
warnings over eastern MO into IL, but given increasing coverage in
central IL and the right flank laying down orthogonal to the
inflow will be the focus for flash flooding in addition to urban
areas.

This activity will progress into Indiana this afternoon and
further discussions are likely.

Jackson

ATTN...WFO...DVN...EAX...ILX...IND...IWX...LMK...LOT...LSX...PAH...SGF...

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

LAT...LON   41248926 41218700 40118643 38998649 38228721
            37888830 38178932 38189029 37849235 38059308
            38439333 38899204 39359064 40089034 40959066

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