Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Mon Sep 15 2025
Valid 151200Z - 161200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN WY TO WESTERN
SD...NORTHEAST NC...AND FAR NORTHERN MN...
...SUMMARY...
Isolated severe gusts are possible across Wyoming into western South
Dakota this afternoon to early evening. Isolated severe hail and
damaging wind are possible across far northern Minnesota in the
early to mid-afternoon. A brief tornado is possible in the northeast
North Carolina vicinity in the early morning Tuesday.
...WY to western SD...
A shortwave trough over the Northwest will gradually move east, with
multiple embedded vorticity maxima rotating through the base of the
trough. The most substantial of which should yield favorably timed
large-scale ascent with peak depth of the boundary layer this
afternoon. A belt of enhanced 500-mb west-southwesterlies should
progress from the ID/UT/WY border area towards the Black Hills
during the afternoon and evening. Scattered convection across
northwest WY during the late morning to midday will intensify as it
spreads across northeast WY to western SD, with more isolated
activity developing southward by late afternoon. With meager
buoyancy, high-based/lower-topped convection will be conducive to
sporadic, outflow-dominated strong/severe gusts. This threat should
diminish later in the evening, especially as nocturnal boundary
layer cooling accelerates after sunset.
...Northeast NC vicinity...
A weak cyclone should approach but likely remain just offshore of
the Outer Banks through 12Z Tuesday. A belt of enhanced low-level
winds should strengthen to its northwest, although guidance has
large spread in amplitude. The more aggressive guidance indicates
that high PW air will be advected across the Outer Banks and
Albemarle Sound vicinity by early morning Tuesday. Near 70 to low
70s F surface dew points by would provide adequate buoyancy for a
conditional tornado threat if low-level hodograph curvature is
enlarged. 00Z HREF and experimental CAMs indicate enough support to
warrant a low-probability tornado highlight.
...Far northern MN...
A conditional threat for a brief severe storm or two is apparent
along the international border. The corridor of peak low-level
theta-e, characterized by upper 60s to low 70s surface dew points,
across northwest MN to northeast IA should pivot east with the
gradual northward progression of the negative-tilt shortwave trough
over the Dakotas. While CAM guidance varies, consensus suggests
isolated afternoon storms should commence in an arc across southeast
MB/northwest ON towards the MN border. Despite a meridional
deep-layer wind profile, this could be semi-orthogonal to the arc's
orientation and would be conductive to mid-level updraft rotation.
But whether storms are able to be sustained in the CONUS or remain
confined within Canada is uncertain.
...MO/AR vicinity...
Within a weakly sheared but amply buoyant airmass, a few strong
gusts are possible this afternoon from pulse-type microbursts.
..Grams/Squitieri.. 09/15/2025
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