AWUS01 KWNH 251138
FFGMPD
ILZ000-MOZ000-251536-

Mesoscale Precipitation Discussion 0845
NWS Weather Prediction Center College Park MD
737 AM EDT Sat Jul 25 2026

Areas affected...Western IL

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

Valid 251136Z - 251536Z

SUMMARY...Persistent convection focused along a narrow axis of
low-level convergence will pose a localized flash flood threat
near the MO/IL border. Continued backbuilding and cell training
could support localized hourly rainfall of 2-3".

DISCUSSION...Regional radar and IR satellite imagery indicate a
small-scale but resilient area of strong convection ongoing near
the Missouri/Illinois border. This activity is anchored along a
maximum in 925-850 mb low level convergence, which is interacting
with a relatively narrow corridor of instability. Mesoanalysis
indicates moderate instability with CAPE values hovering around
1000 J/kg, co-located with an anomalously moist airmass featuring
PW values in excess of 2.0 inches.

While the overall footprint of favorable ingredients remains
narrow, upstream convective development into the low level flow is
actively supporting localized cell training. Satellite trends show
a persistent and robust updraft that has outlasted recent HRRR
runs which attempted to weaken and move the activity eastward too
quickly. While IR imagery does not suggest the system is growing
upscale into a broader convective complex, the central area of
strong updrafts is persisting.

Over the next few hours, this convection will likely remain
small-scale, but it should gradually expand slightly eastward as
the 925?850 mb moisture transport axis shifts in that direction.
Concurrently, backbuilding on the western flank will remain a
concern. Given the 2"+ PWAT airmass, efficient rainfall production
will support localized hourly rainfall as high as 2-3" within the
strongest cores, resulting in an isolated flash flood risk for
low-lying and sensitive drainage areas.

Chenard


ATTN...WFO...ILX...LSX...PAH...

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

LAT...LON   39569005 39238946 38698900 38238892 38048932 
            38098982 38659027 38829035 39139060 39389058 
            
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