ACUS01 KWNS 211234
SWODY1
SPC AC 211232

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0732 AM CDT Mon Jul 21 2025

Valid 211300Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...

...SUMMARY...
Severe thunderstorms capable of producing large hail, severe gusts,
and perhaps a tornado or two will be possible today and tonight
across parts of the northern Plains. Additional isolated strong to
severe storms may occur across portions of the central Plains.

...Northern Plains into the Upper Midwest...
A long-lived and compact MCS has advanced into parts of west-central
MN this morning. This convection is on the northern periphery of
meaningful low-level moisture and related instability. It should
generally weaken over the next few hours while it tracks
southeastward over southern MN as a low-level jet gradually lessens.
But in the short term, it may still be capable of producing
occasional strong to severe wind gusts. Behind this activity, a
moist and rather unstable airmass will exist across the northern
Plains along and south of a convectively reinforced front that
should become oriented generally east-west along the ND/SD border by
late this afternoon. Large-scale ascent across the northern Plains
will likely be weak for much of the day, as upper ridging remains
prominent over the central CONUS.

Even so, there are indications that a weak mid-level perturbation
emanating from upper troughing over the Pacific Northwest should
overspread the northern Rockies and adjacent High Plains of
central/eastern MT by mid/late afternoon as ample daytime heating of
a slowly moistening low-level airmass occurs. A belt of enhanced
west-southwesterly mid-level flow will accompany this feature,
supporting ample veering/strengthening of the wind profile with
height through mid/upper levels. Related strong deep-layer shear of
40-50+ kt will easily support supercells with initial development
off the Bighorns given the presence of at least moderate instability
across the High Plains. Large hail will be possible with these
supercells this afternoon, followed by an increasing severe wind
threat with time this evening/overnight into parts of the Dakotas as
convection potentially grows upscale, and where ample MUCAPE and
strong deep-layer shear will be present along/north of the surface
boundary. The development of elevated supercells also appears
possible across parts of the Dakotas late tonight as a low-level jet
gradually strengthens, with a related threat for at least isolated
severe hail if they occur.

...Central Plains...
Much of the central Plains will remain capped today, as the upper
ridge and warm temperatures aloft exert their influence. A surface
trough is expected to extend southward across the central High
Plains this afternoon, and a remnant MCV related to earlier
convection should move eastward along/near the NE/KS border. Both of
these features may aid in at least isolated thunderstorm development
this afternoon, in the presence of moderate to strong instability
amid modest deep-layer shear. Isolated severe hail and wind gusts
may occur with any of the more robust cores that can develop and be
maintained in an otherwise weak forcing regime. The Marginal Risk
has been expanded southward a little to include more of northern KS
and southeast NE, where strong to severe convection may develop
later today in close proximity to the MCV.

...Tennessee Valley into the Southeast...
A weak MCV related to ongoing convection across MO and southern IL
this morning will track southeastward across the TN Valley and
vicinity through this afternoon. Modest west-northwesterly flow
should be in place today across parts of the OH/TN Valleys into the
Southeast. This may support loosely organized multicells and pulse
thunderstorms today, as mostly sunny conditions aid in the
development of moderate to locally strong instability this
afternoon. While deep-layer shear is forecast to remain weak, some
of this convection may still be capable of producing strong to
locally damaging winds. Parts of these regions may be considered for
inclusion in a Marginal Risk in a later outlook update, pending
additional observational/model trends.

..Gleason/Bentley.. 07/21/2025

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