Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Fri Aug 15 2025
Valid 160100Z - 161200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
THE OVERNIGHT HOURS ACROSS PARTS OF CENTRAL AND EASTERN SOUTH
DAKOTA...NORTHERN NEBRASKA...SOUTHWESTERN MINNESOTA...NORTHWESTERN
IOWA...PARTS OF SOUTHEASTERN IOWA AND SOUTHWESTERN WISCONSIN...
...SUMMARY...
An organizing cluster of thunderstorms with potential to produce
strong to severe wind gusts may still evolve later this evening into
the overnight hours across parts of the middle Missouri Valley and
adjacent Great Plains.
...01Z Update...
Stronger westerlies remain generally confined to the higher
latitudes, near/north of the Canadian/U.S. border. To the southwest
of one significant embedded short wave trough crossing the Hudson
Bay and northern Ontario vicinity, modest westerly mid-level flow
(including speeds of 30-40 kt around 500 mb) is overspreading areas
as far south as the Dakotas into Upper Midwest, near the northern
periphery of mid-level ridging. Forcing associated with subtle
perturbations embedded within this regime has contributed to several
developing clusters of storms. A couple now propagating east of
the upper Mississippi Valley appear to be in the process of
weakening, likely due to some combination of weak/weakening lift and
increasing inhibition beneath relatively warm mid-level temperatures
encompassing much of the northern and central Great Plains into
Midwest.
Beneath steeper mid-level lapse rates upstream, boundary-layer
moisture east of the lee surface trough across the high plains is
still contributing to strong to extreme potential instability across
much of central and eastern South Dakota/Nebraska, as scattered high
based convection emerges from eastern Wyoming and northeastern
Colorado. It appears possible that low-level forcing for ascent,
near the nose of a nocturnally strengthening southerly low-level
jet, could contribute to a consolidating and upscale growing
cluster, particularly as activity acquires more unstable inflow
later this evening into the overnight. Various model output,
including the NAM and Rapid Refresh, suggest that the evolution of a
notable convective perturbation is possible, which could be
accompanied by a swath of strong to severe wind gusts.
..Kerr.. 08/16/2025
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