Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1200 AM CDT Tue Aug 11 2026
Valid 111200Z - 121200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHERN
ILLINOIS INTO THE OHIO VALLEY...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...AND FROM IOWA TO VIRGINIA...
...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...
A complex forecast scenario is expected today from IA into the Ohio
Valley and adjacent Appalachia. More than one MCS may be ongoing at
the beginning of the period. The first across IA/southern MN, and
one further southeast across parts of the Midwest (exact location is
uncertain, but most likely IN/OH). Possible early day convection
across IN/OH will spread east/southeast across the Ohio Valley
during the morning posing risk for strong gusts. This activity is
likely to emerge across Appalachia, and eventually VA and the
broader Mid-Atlantic during the afternoon/evening. How much
destabilization will occur across VA and the Mid-Atlantic remains
uncertain given prior convection the previous day and potential
convective debris across the region. Some damaging wind potential
could materialize if sufficient destabilization occurs during the
afternoon.
The anticipated MCS over IA/southern MN early in the forecast period
is then expected to continue east/southeast across the Midwest,
fueled by a very moist and strongly unstable boundary layer.
Midlevel flow is forecast to be quite strong (by August standards),
with forecast guidance suggesting 700 mb greater than 60 kt
spreading across the Midwest through evening. While the exact
evolution of a potential severe MCS moving across the Midwest is
uncertain, it is possible the morning activity over IA will develop
southeast along outflow across the Ohio Valley. Given the strong
kinematic field and ample instability, if a well organized MCS is
maintained from IA southeast into the OH Valley, a swath of damaging
gusts (some 75+ mph) will be possible.
...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 a lack of 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.
..Leitman/Moore.. 08/11/2026
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