Weather Prediction Center issues Mesoscale Precipitation Discussion #1089 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE402
AWUS01 KWNH 191854
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OHZ000-INZ000-ILZ000-MOZ000-IAZ000-200050-
Mesoscale Precipitation Discussion 1089
NWS Weather Prediction Center College Park MD
254 PM EDT Wed Aug 19 2026
Areas affected...Parts of the Midwest and Ohio Valley
Concerning...Heavy rainfall...Flash flooding possible
Valid 191850Z - 200050Z
SUMMARY...Slow-moving thunderstorms along a nearby frontal
boundary extending across the Midwest and Ohio Valley may contain
rainfall rates around 2"/hr at times. Totals could exceed 3"
through 8pm CDT in spots and lead to scattered instances of flash
flooding within a region containing saturated soils. Uncertainty
remains with respect to coverage of the most intense rainfall
rates and will be monitored in future discussions if the flash
flood threat appears more significant.
DISCUSSION...Latest regional radar mosaic across the Midwest and
Ohio Valley depict smaller scale showers/thunderstorms developing
along a slow-moving frontal boundary across southern IA, with
scattered storms also developing within the warm sector across
central IL/IN. This is all occurring ahead of an approaching short
wave diving across IA/NE and pushing eastward. This feature will
help spark additional thunderstorms that will focus along and just
south of the aforementioned frontal boundary.
Rainfall rates are expected to reach up to around 2"/hr given
1000-2000 J/kg MLCAPE and PWs of 1.5-2.0" in the area. 850mb flow
is relatively weak and out of the west (5-15 kts), but will shift
throughout the late-afternoon and evening as a mid-level wave
crosses the region. This will not only provide more focus for
thunderstorms, but weaken the flow briefly and maintain a threat
for slow-moving cells and/or cell mergers. These ingredients
support maximum rainfall totals over 3" and within a region where
6-hr FFG remains mostly below 3" due to extreme rainfall over the
past week or so. 1-hr FFG is below 2" for most areas and even
below 1.5" in parts of central IL and east-central IN/west-central
OH. Should the most intense rainfall rates overlap with these
sensitive regions, flash flooding would be more likely and could
be locally significant. These details will continue to be
monitored.
Snell
...Please see www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...DMX...DVN...EAX...ILN...ILX...IND...IWX...LOT...
LSX...
ATTN...RFC...KRF...MSR...TIR...NWC...
LAT...LON 41339045 41258798 41138562 40738393 39858395
39158655 39038930 39599182 39819468 40809469
41069292
Source:
Weather Prediction Center issues Mesoscale Precipitation Discussion #1089 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE---------------
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