Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1247 AM CDT Thu Sep 17 2026
Valid 171200Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE INTERMOUNTAIN WEST AND IN THE CENTRAL HIGH PLAINS...
...SUMMARY...
Thunderstorms with isolated severe wind gusts and hail will be
possible in parts of the Intermountain West late this afternoon and
early this evening. A few strong gusts may also occur in parts of
the central High Plains.
...Intermountain West...
An upper-level low will move inland into the Intermountain West
today, as southwest flow remains at mid-levels over much of the
region. At the surface, a trough will deepen from southern Idaho
into western Utah. To the east of the trough, dewpoints in the 50s
F, will contribute to weak instability by afternoon. As surface
temperatures warm, thunderstorms will develop in the higher terrain.
RAP forecast soundings to the east of the trough at 00Z have 0-6 km
shear in the 30 to 40 knot range. In addition, low to mid-level
lapse rates are forecast to be in the 6.5 to 7.5 C/km range. This
environment will likely support an isolated threat for severe gusts
and hail. The threat should be concentrated during the late
afternoon and early evening, as cell coverage maximizes near the
instability axis.
...Central High Plains...
An upper-level ridge will move eastward today across the
north-central U.S, as a shortwave trough embedded in the ridge moves
through the central High Plains. At the surface, a warm front is
forecast to move slowly northward across southern and western
Nebraska this afternoon. An axis of moisture, with surface dewpoints
in the 60s and 70s F, will be oriented north of the front from the
mid Missouri Valley west-northwestward into the central High Plains.
During the late afternoon, scattered thunderstorms are expected to
develop near the shortwave trough, with storms moving gradually
northeastward across the central High Plains. Forecast soundings
near the area of greatest expected convective coverage have moderate
deep-layer shear suggesting an isolated severe threat will be
possible. However, lapse rates are forecast to be poor, which should
keep any severe threat marginal. If storms near the front can remain
nearly surface-based, then an isolated wind-damage threat could
develop, mainly during the early to mid evening, as low-level flow
increases.
..Broyles/Thornton.. 09/17/2026
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