ACUS01 KWNS 111228
SWODY1
SPC AC 111226

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0726 AM CDT Tue Aug 11 2026

Valid 111300Z - 121200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHERN
ILLINOIS INTO THE OHIO VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...AND FROM EASTERN IOWA TO VIRGINIA AND NORTH CAROLINA...

...SUMMARY...
Severe thunderstorms with damaging wind gusts will be possible today
from the eastern Iowa/northern Illinois vicinity into parts of the
Ohio Valley and central Appalachians. Areas of severe wind gusts
and hail will also be possible over parts of the northern Plains.

...IA to the Mid-Atlantic and Southeast...
An uncertain and inherently complex forecast is apparent this
morning from IA east-southeastward into the central Appalachians.
An impulse embedded within west-northwest flow and an overnight MCV
moving into IA from NE appear to be aiding in MCS development this
morning over eastern IA, with this thunderstorm complex moving into
northern IL through the late morning.

While the exact evolution of a potential severe MCS moving across
the Midwest is uncertain, a possible scenario is the thunderstorm
activity over IA either merges with additional storms developing
ahead of it or it continues to intensify into the main severe-wind
producing MCS. Another severe cluster is located over eastern IN
within the eastern envelope of the EML. Considered higher wind
probabilities to be delineated this outlook update, but it remains
unclear regarding sequential details that would lead to a
high-confidence mesoscale corridor of severe wind and associated
wind damage. Nonetheless, environmental parameters (e.g., very rich
moisture, steep 700-500 mb lapse rates, adequate deep-layer shear)
will strongly favor the development of mature/severe linear
clusters/bows with the more intense storms that eventually evolve
today. This activity will likely move along a large CAPE gradient
that will likely be reinforced by early morning convection.
Scattered severe gusts (60-85 mph) will be likely in the favored
mesoscale corridors with swaths of concentrated wind damage. A
lower but appreciable severe risk may extend into VA and NC with a
lower severe threat with south extent into SC/GA.

...Northern Plains...
East/southeasterly flow along the surface trough is forecast to
maintain 60s F dewpoints across the western Dakotas and parts of NE
this afternoon. Steep midlevel lapse rates atop the relatively
moist boundary layer, and strong heating will support a corridor of
moderate to strong instability across the western Dakotas.
Scattered storms are expected by early evening amid supercell wind
profiles. Elongated hodographs favorable for splitting cells with
an accompanying risk for large to very large hail are forecast.
Isolated severe gusts also could occur. Given the lack of a
stronger low-level jet during the nighttime hours, it appears
unlikely that upscale growth will occur, and convection is expected
to wane with eastward extent overnight.

...Mojave Desert of CA...
Early morning radar imagery shows an MCV moving slowly northwest
over the lower CO River Valley and this feature is likely associated
with a weak disturbance moving northwest into southern CA. The
airmass across the desert will undergo strong heating in wake of
early day cloud debris. Another likely convectively augmented
mid-level impulse will move across southern AZ towards southern CA
today. Widely scattered thunderstorms are forecast to develop this
afternoon amid a seasonably moist airmass and an inverted-V
thermodynamic profile is depicted in forecast soundings. Isolated
severe gusts are possible with the more intense downdrafts.

..Smith/Kerr.. 08/11/2026

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