Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Mon Aug 17 2026
Valid 180100Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN PLAINS...AND FROM NORTHEASTERN ALABAMA INTO
WESTERN NORTH CAROLINA...
...SUMMARY...
Thunderstorms with severe wind gusts and large hail are expected
this evening across parts of the central and northern Plains.
Isolated severe gusts will also be possible from parts of the
northern Gulf Coast States into the southern Appalachians and
Carolinas.
...Central and Northern Plains...
The latest water vapor imagery shows west-northwesterly flow over
much of the northern U.S., with a low-amplitude shortwave trough
moving through the flow in the northern Plains. At the surface, a
cold front is advancing southeastward through the Dakotas. Ahead of
the front, surface dewpoints are in the 60s F. The RAP has an axis
of moderate to strong instability located from central Nebraska
northeastward into eastern South Dakota, along which MLCAPE is
estimated in the 2500 to 3500 J/kg range. Isolated thunderstorms are
ongoing near the instability axis with scattered storms ongoing to
the west of the instability max in western Nebraska and southwestern
South Dakota.
These storms are located along the eastern edge of an elevated mixed
layer extending eastward from the central Rockies. Near the storms,
the RAP is estimating 700-500 mb lapse rates in the 7.5 to 8.5 C/km
range. In addition, the North Platte WSR-88D VWP has 0-6 km shear
near 50 knots with significant directional shear evident in the
lowest 3 km above ground level. This environment will support
supercells with large hail and severe wind gusts this evening. The
more intense storms could produce hailstones exceeding 2 inches in
diameter. Short-term model forecast suggest that the storms will
continue to move east-southeastward toward the instability axis this
evening, remaining relatively discrete. However, a transition to a
broken line segment should eventually occur, which would result in a
greater wind-damage threat. A few severe gusts above 75 mph will be
possible. The severe threat should persist into the mid to late
evening...See MCD 2019.
...Northern Gulf Coast States/Southern Appalachians/Carolinas...
The latest surface analysis shows a distinct outflow boundary from
northern Alabama eastward into the western Carolinas. Strong to
severe thunderstorms are ongoing near the outflow boundary. To the
south of the boundary, surface dewpoints are in the 70s F and the
RAP is estimating MLCAPE in the 2000 to 3500 J/kg range. Within the
most unstable air, RAP forecast soundings early this evening have
0-3 km lapse rate in the 7.5 to 8 C/km range, with precipitation
water above 2 inches. In addition, the WSR-88D VWP in northeast
Alabama has 0-6 km shear in the 20 to 25 knot range. This
environment will support a potential for severe wet downbursts for a
couple more hours this evening.
..Broyles.. 08/18/2026
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