Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0253 PM CDT Tue Jul 22 2025
Valid 222000Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE
NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY...
...SUMMARY...
Scattered severe thunderstorms will be possible over parts of the
northern Plains into the upper Mississippi Valley this afternoon
into tonight.
...20z Update...
Minor updates were made to the D1 Convective Outlook to reduce the
Marginal Risk area across North Dakota into northern Minnesota where
the front has shifted southward with influence from morning
convection.
Otherwise, the Slight Risk across the northern Plains into the upper
Midwest remains on track. There continues to remain some uncertainty
on what the corridor for greater wind risk will be this evening.
Cloud cover remains across much of the Slight Risk area. It is
mostly clear across southern South Dakota into Wyoming, where
temperatures are warming. Thunderstorm activity has begun across the
high terrain in Montana and Wyoming. See the previous discussion
below for more information.
..Thornton.. 07/22/2025
.PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Jul 22 2025/
...Northern Plains into the Upper Mississippi Valley...
Visible-satellite imagery late this morning shows extensive cloud
debris and convective outflow from ongoing and early morning
shower/thunderstorm activity. A composite outflow/front is draped
from the ND/MN Red River Valley west-southwestward into northwest
SD, with another frontal segment extending into northern WY. Weak to
neutral height rises across the northern Plains this afternoon will
likely not support a northward oscillation of the boundary into
southwest ND.
A belt of moderate to strong southwesterly 500-mb flow overhead the
north-central Rockies and adjacent plains will be downstream of a
larger-scale trough pivoting east across the northern Rockies
through tonight. In agreement with earlier forecast thinking, it
appears probable that diurnal storms will favor the general area of
northern WY/southern MT. This region will generally be post-frontal,
but steep mid-level lapse rates and a modestly moist low-level
airmass should still aid in the development of at least weak
instability. Strong deep-layer shear should support supercells
initially, with associated threat for large to perhaps isolated very
large hail. Some potential should exist for this convection to grow
upscale this evening across parts of the Dakotas and pose a greater
threat for severe/damaging winds overnight. But, uncertainty remains
high regarding the placement of this possible cluster, and whether
it will remain surface-based or elevated.
Farther east into the upper MS Valley, it appears less likely that
robust convection will develop before this evening due to the
stabilizing influence of the ongoing morning activity. If
thunderstorms can develop later, most short-term guidance continues
to suggest that sufficient airmass recovery will occur to support
severe convection with mainly a hail/wind threat. Some diurnal
hail/wind threat may develop across IA in association with the lower
MO Valley MCV. Uncertainty remains high regarding this scenario.
...Central High Plains...
Scattered to numerous high-based thunderstorms should develop this
afternoon along/near the surface lee trough extending southward
across the central High Plains. While low/mid-level flow and
deep-layer shear are all expected to remain weak today across this
region due to closer proximity to the upper ridge, heating will
contribute to the development of steep 0-3 km lapse rates. Severe
gusts will be the primary hazard.
...Southeast...
A weak cold front will shift southward today across parts of GA/SC.
A rather moist low-level airmass will be in place ahead of the
front, with daytime heating encouraging the development of moderate
to locally strong instability through the afternoon. Scattered
thunderstorms that develop along/ahead of the front, and along
various sea breeze circulations, may be capable of producing
occasional damaging winds, even though shear will remain weak.
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