Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0700 AM CDT Wed Jul 23 2025
Valid 231300Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS INTO THE UPPER MIDWEST AND UPPER GREAT LAKES...
...SUMMARY...
Severe thunderstorms capable of producing damaging winds and
potentially a tornado risk are expected across the middle Missouri
Valley and Upper Midwest to upper Great Lakes, mainly this afternoon
and evening. Large hail may occur with supercells later today across
parts of the northern High Plains.
...Synopsis...
A positively tilted upper trough over central Canada and the
northern Rockies/High Plains will advance slowly eastward today,
impinging on an upper ridge that will remain over much of the
Southeast, Mid-Atlantic, and OH Valley. A quasi-stationary surface
front arcing northeastward from a weak low in central SD should make
some southeastward progress as a cold front today across portions of
the northern Plains and Upper Midwest, as a low-amplitude mid-level
shortwave trough advances eastward across these regions through the
period. This front will likely serve as a continued focus for strong
to severe convection today.
...Mid Missouri Valley into the Upper Midwest/Great Lakes...
Scattered to numerous thunderstorms are occurring this morning,
generally along/north of the surface front across north-central SD
into northern MN. This activity may tend to remain somewhat elevated
through most of the morning, but it may still pose an isolated
severe hail/wind threat given the presence of moderate MUCAPE and
sufficient deep-layer shear to support updraft organization. A
separate band of elevated convection is ongoing along/near the NE/SD
border. This activity is likely more tied to low-level warm
advection, and it remains somewhat unclear what affect these
thunderstorms will have on the warm sector later today if they can
persist.
Regardless of the uncertainty with the evolution and intensity of
ongoing thunderstorms this morning, daytime heating along/south of
the front will likely aid in strong to locally extreme instability
developing by early to mid afternoon, as a very moist airmass is
already in place across the Upper Midwest per area surface
observations. Mid-level flow and related deep-layer shear will tend
to become more modest with southward extent along the surface front.
But, they should still be sufficient to promote organized severe
convection, especially across MN into WI.
Current expectations are for multiple bowing clusters/line segments
to develop this afternoon along much of the front from NE into
eastern SD and MN. Scattered severe/damaging winds will likely be
the primary threat with this activity as it spreads eastward into
parts of northern WI and the U.P of MI this evening. Isolated hail
may occur with initial development. Modest low-level shear may also
support some tornado threat, mainly across parts of MN into WI where
a southwesterly low-level jet should be focused later this
afternoon/early evening. To account for both the ongoing activity
and recent guidance trends suggesting an earlier/westward start to
robust thunderstorms this afternoon along the front, the Marginal
and Slight Risks have been expanded westward some across NE/SD/MN
with this update.
...Northern/Central High Plains...
Within a post-frontal environment, east-northeasterly low-level
winds will persist beneath moderately strong westerlies aloft to
yield relatively long/straight hodographs at mid/upper levels, with
generally 40-50 kt of effective bulk shear from the Black Hills
vicinity northward. This will coincide with moderate diurnal
destabilization, particularly across interior/eastern Wyoming into
southeast Montana and parts of the western Dakotas. Scattered large
hail may occur with any sustained supercells, along with the
possibility of some severe wind gusts, particularly if
east-southeastward moving clusters can develop this evening. With
increased confidence in multiple supercells occurring this
afternoon/evening across northeast WY/southeast MT into western SD,
have introduced a Slight Risk mainly for large hail potential.
..Gleason/Grams.. 07/23/2025
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