274
ACUS11 KWNS 152252
SWOMCD
SPC MCD 152252
ILZ000-WIZ000-IAZ000-160015-

Mesoscale Discussion 1956
NWS Storm Prediction Center Norman OK
0552 PM CDT Fri Aug 15 2025

Areas affected...portions of eastern/southeastern Iowa into
northwestern Illinois

Concerning...Severe Thunderstorm Watch 590...

Valid 152252Z - 160015Z

The severe weather threat for Severe Thunderstorm Watch 590
continues.

SUMMARY...A well organized bowing cluster should continue across
southeastern IA into northwestern IL this evening. Damaging gusts
(some 70+ mph) are likely.

DISCUSSION...As of 2245 UTC, regional radar imagery shows a stronger
bowing cluster has emerged from the initial convection of storms
over eastern IA. Downstream, a very unstable environment (4000-5000
J/kg of SBCAPE) remains in place. While vertical shear (25-35 kt) is
expected to decrease with southern extent, evidence of an elevated
rear-inflow jet and a 20-25 deg F cold pool, along with the degree
of buoyancy suggest maintenance of this complex is likely for at
least a few more hours. With several gusts to 70+ mph observed over
the 60 minutes, damaging winds remain likely across
eastern/southeastern IA, into northwestern and possible
north-central IL this evening.

CAM guidance has not handled the convective evolution particularity
well thus far, with only a few outlier solutions capturing the
intensity of the bow. This lends lower confidence to the downstream
severe risk this evening. However, the continued favorable
environment and well-organized radar presentation of the system does
suggest at least some damaging wind potential may occur downstream
of the eastern edge of WW590 in IL tonight. Conditions will continue
to be monitored should an additional watch be needed later this
evening.

..Lyons.. 08/15/2025

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...DMX...

LAT...LON   42319219 42829123 42689053 42428952 42228929 41438913
            40788942 40379060 40859212 41289261 41679301 41939305
            42319219

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 95 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN