546
ACUS01 KWNS 180557
SWODY1
SPC AC 180555

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Fri Sep 18 2026

Valid 181200Z - 191200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
THE CAROLINAS INTO NORTHERN GEORGIA...IN THE MID MISSOURI VALLEY AND
IN THE INTERMOUNTAIN WEST...

...SUMMARY...
Thunderstorms with isolated severe wind gusts may develop late this
afternoon and early this evening from the Carolinas into northern
Georgia, and in the mid Missouri Valley. Isolated severe gusts and
hail will also be possible in parts of the Intermountain West.

...Carolinas/Northern Georgia...
At the surface, a cold front will move southward into the
Mid-Atlantic today. Ahead of the front, a moist airmass will be in
place over much of the Carolinas extending southwestward into
northern Georgia. Surface dewpoints within this airmass will be in
the 60s to near 70 F. As surface temperatures warm today, an axis of
moderate instability will develop along the moist axis. In response
to surface heating, scattered thunderstorms will form in the higher
terrain of the southern Appalachians and move southward into the
southern Appalachian foothills. The thermodynamic environment may be
enough to support an isolated wind-damage threat, mainly in the late
afternoon and early evening when low-level lapse rates become
steepest.

...Eastern Nebraska/Iowa...
Mid-level heights will gradually fall today over much of the
north-central U.S., as a ridge pattern breaks down. At the surface,
a well-defined moist axis will be in place from the mid Mississippi
Valley northwestward into the mid Missouri Valley. Surface dewpoints
along and near this axis will be in the lower to mid 70s F. In
response to surface heating, a reservoir of moderate instability
will be in place by afternoon over much of Iowa. Low-level
convergence is forecast to become maximized during the afternoon
along the instability axis, and further west to near a surface low
over the mid Missouri Valley. Thunderstorm development will be most
likely this afternoon on the northern end of the stronger
instability from far southeast Minnesota into northern Iowa. Enough
instability and deep-layer shear should be in place for isolated
severe wind gusts. Although conditional, the threat could develop
southwestward over the remainder of Iowa during the early evening,
as a low-level jet strengthens across the region.

...Intermountain West...
A mid-level trough will move eastward across the Intermountain West
today. Southwest flow aloft will be in place ahead of the trough
over much of the region. At the surface, dewpoints in the 50s F are
expected from northern Utah into valleys of western Wyoming, where
the RAP is forecasting MLCAPE to peak in the 1000 to 1200 J/kg
range. In addition to the instability, forecast soundings show
moderate deep-layer shear in response to the approaching mid-level
trough. As low to mid-level lapse rates become steep in the late
afternoon and early evening, isolated severe gusts and hail will be
possible.

..Broyles/Thornton.. 09/18/2026

$$