ACUS01 KWNS 081233
SWODY1
SPC AC 081231

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0731 AM CDT Tue Sep 08 2026

Valid 081300Z - 091200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
CENTRAL IOWA AND FAR EASTERN NEBRASKA...

...SUMMARY...
Widely scattered severe storms capable of mainly severe wind gusts
appear possible across portions of Iowa and eastern Nebraska Tuesday
afternoon and evening. More sporadic occurrences of severe winds and
large hail may occur from portions of the upper Midwest into the
central Plains.

...Central Plains into the upper Midwest...
An extensive low-level jet is currently in place from the southern
High Plains through the Upper Midwest. Warm-air advection associated
with this feature is contributing to showers and thunderstorms from
eastern NE through WI and into western Upper MI. This activity is
forecast to gradually shift northeastward this morning while the
embedded storms also gradually diminish in strength. These showers
and thunderstorms, and associated warm low to mid-level
temperatures, are expected to limit destabilization across much of
WI and Upper MI.

Some moderate buoyancy is possible by the early afternoon across MN,
just ahead of a cold front pushing eastward into the region.
Lingering convective inhibition will likely limit convective
initiation, and considerable uncertainty exists regarding
thunderstorm coverage. This uncertainty precludes introducing any
severe probabilities, but the combination of moderate buoyancy and 
strong deep-layer shear over the region would support some severe
potential with any updrafts that persist and mature.

Farther south and west (i.e. from IA through eastern/southern NE
into northern KS), stronger daytime heating will contribute to a
well-mixed boundary layer, characterized by steep low-level lapse
rates and dewpoints in the 60s to low/mid 70s F. This air mass is
expected to become moderately to strongly unstable by late afternoon
with MLCAPE of 2000-3000 J/kg. Thunderstorm development is expected
as the southeastward-progressing cold front interacts with this
destabilized and buoyant airmass. The stronger vertical shear will
be displaced north/northeast of the greater buoyancy, but 30 to 35
kt of effective bulk shear is still sufficient for some storm
organization. A largely parallel shear-vector orientation with the
front suggests that initial storms should grow upscale quickly into
line segments or broken bands, with some tendency for undercutting
as well. Even so, a few damaging wind gusts will be possible from
mid afternoon through evening. The low-level jet will increase again
from western KS through central IA this evening resulting in a
corridor of stronger low-level shear. This low-level shear will
support a low-probability tornado risk,  but a more robust threat is
expected to be limited by largely outflow-dominant and/or elevated storms.

...CO Plains into western KS...
Thunderstorm development appears likely across the higher terrain of
central CO as the mid-level flow veers more westerly during the late
afternoon. Moist post-frontal northerly low-level flow is expected
across the CO Plains and western KS this evening, which could result
in enough buoyancy to maintain modest intensity as the central CO
storms progress eastward. High-based storm character and prevailing
steep low-level lapse rates may result in a few stronger gusts as
this cluster moves eastward into western KS.

..Mosier/Lyons.. 09/08/2026

$$
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