645
ACUS01 KWNS 190102
SWODY1
SPC AC 190100

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 PM CDT Tue Aug 18 2026

Valid 190100Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND LOWER MISSOURI VALLEY...

...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
evening from parts of the central Plains into the lower Missouri
Valley. Isolated severe gusts and hail will also be possible in
parts of the central and northern High Plains, and from the Midwest
into the Great Lakes.

...Central Plains/Lower Missouri Valley...
The latest water vapor imagery shows west-northwesterly mid-level
flow over the central U.S. with a shortwave trough embedded in the
flow over western Kansas. At the surface, a moist airmass is located
from the mid Mississippi Valley westward into the central Plains,
where surface dewpoints are mostly from the upper 60s and lower 70s
F. Low-level convergence is maximized along and near a well-defined
outflow boundary located across central Kansas. Isolated severe
thunderstorms are ongoing near this boundary. In this area, moderate
deep-layer shear and steep low to mid-level lapse rates will be
favorable for isolated large hail and severe wind gusts over the
next few hours.

Further to the north across northern Kansas and southern Nebraska,
the RAP has strong instability analyzed with MLCAPE in the 3000 to
3500 J/kg range. Thunderstorms are currently ongoing in western
Nebraska and northeastern Colorado. These storms will move toward
the stronger instability over the next few hours. As this happens,
the storms may increase in intensity. If this were to occur, the
strong instability and moderate deep-layer shear over northwest
Kansas and southwest Nebraska would support a threat for hail and
isolated severe wind gusts. A second severe threat area is expected
to become active further east from northeast Kansas into
west-central Missouri as low-level flow increases this evening.
Thunderstorms are now developing in north-central Kansas and this
convection should expand in coverage over the next couple of hours.
The primary threat would be wind damage, especially if a short
intense line segment can become organized. Along its path, severe
wind gusts could exceed 70 mph...see MCD 2031.

...Midwest/Great Lakes...
The latest water vapor imagery shows a distinct shortwave trough
over the mid Mississippi Valley within west-northwesterly flow
aloft. At the surface, a moist airmass is located from the mid
Missouri Valley east-northeastward into the lower Michigan, where
surface dewpoints are mostly in the upper 60s and lower 70s F. An
axis of low-level convergence is located from northern Iowa into far
southern Wisconsin, along which thunderstorms are ongoing. A couple
of cells have remained discrete across northwestern Iowa, where an
axis of moderate instability is analyzed. As these cells move
southeastward into north-central Iowa this evening, isolated large
hail and a few severe wind gusts will be possible. Further east, the
storms have organized into a line segment over far southern
Wisconsin. These storms will have an isolated wind-damage threat
over the next couple of hours. A marginal severe threat may also
continue over parts of lower Michigan early this evening.

...Central and Northern High Plains...
West-northwesterly mid-level flow is currently located across the
northern Rockies and northern High Plains, with a distinct shortwave
trough moving through Montana. At the surface, an axis of low-level
moisture is present from eastern Wyoming into eastern Montana, along
which surface dewpoints are near 60 F. This is contributing to
MLCAPE around 1000 J/kg along parts of the moist axis. Isolated
strong to severe storms are ongoing near the moist axis in far
northeast Wyoming and in northeast Montana. Moderate deep-layer
shear and steep low to mid-level lapse rates will support a
potential for isolated severe gusts and hail this evening.

..Broyles.. 08/19/2026

$$