917
ACUS11 KWNS 281514
SWOMCD
SPC MCD 281514
ILZ000-IAZ000-WIZ000-281715-

Mesoscale Discussion 1366
NWS Storm Prediction Center Norman OK
1014 AM CDT Sun Jun 28 2026

Areas affected...parts of Central into Eastern Iowa into northwest
Illinois

Concerning...Severe potential...Watch possible

Valid 281514Z - 281715Z

Probability of Watch Issuance...40 percent

SUMMARY...Convective trends are being monitored for a possible
increase in damaging wind potential by late morning into early
afternoon. A Severe Thunderstorm Watch is possible.

DISCUSSION...On the southern flank of a long-lived MCS, a more
intense storm has recently developed near Ames, IA, within a
pronounced low-level warm advection pattern, per KDMX VWP.
Mesoanalysis suggests that the storm is located in close proximity
to a stationary front that extends southeast through southeast IA
into central IL. The air mass south of the boundary is very moist
with the presence of steep mid-level lapse rates yielding a
moderately unstable environment with MLCAPE upwards of 2000 J/kg.

The main uncertainty is whether the current storms will become fully
rooted within the boundary layer given the expected strengthening of
the cap at the base of an EML through the day. The 12Z CAMs offer
various scenarios with regard to convective evolution this morning
but by afternoon largely agree that the strengthening cap will
become prohibitive to surface-based storm development. However, in
the event this more recent storm development can establish a cold
pool, the background environment appears supportive of damaging wind
potential in addition to some large hail threat.

..Mead/Guyer.. 06/28/2026

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

ATTN...WFO...DVN...ARX...DMX...

LAT...LON   42179345 42759297 42889227 42338988 41938972 41598995
            41359034 41329113 41679241 42179345

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN