Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0243 PM CDT Wed Jul 23 2025
Valid 232000Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THERE IS A SLIGHT
RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH
PLAINS AND NEBRASKA INTO THE UPPER GREAT LAKES...
...SUMMARY...
Scattered severe thunderstorms capable of producing damaging winds
and potentially a tornado risk are possible across the Upper
Midwest, mainly this afternoon and evening. Large hail may occur
with supercells late today across parts of the northern High Plains.
...20z Update...
The primary forecast amendment for this update is a reduction in
severe probabilities across portions of northern MN and WI where the
primary front and convective clusters/bands have passed and
conditions are slowly stabilizing within the post-frontal regime.
Across WI, 5% tornado probabilities have been adjusted southward to
better align with recent convective trends and where short-range
guidance shows the best overlap of low-level theta-e advection and
wind shear later this evening. Although convective mode will be the
primary modulating factor in the overall tornado threat, STP values
should increase to between 1-2 later this evening as the nocturnal
jet strengthens and should support at least some tornado potential.
Elsewhere, the forecast remains on track per the previous discussion
below. GOES IR imagery and echo top data shows an uptick in
convective intensity across southeast MN and northern WI, and early
stages of convective initiation are noted along the front
southwestward into NE. These trends suggest a severe threat remains
across the Plains/upper MS Valley regions. See MCDs #1761 and #1762
for additional details regarding the severe threat across portions
of the northern High Plains and central NE.
..Moore.. 07/23/2025
.PREV DISCUSSION... /ISSUED 1123 AM CDT Wed Jul 23 2025/
...Mid Missouri Valley into the Upper Midwest/Great Lakes...
Visible satellite/radar composite shows scattered thunderstorms late
this morning from eastern SD into western WI, generally near and
east of a surface low analyzed near the SD/MN border. A cold front
extending from northern MN southwestward into the central High
Plains will continue east-southeastward and provide a focus for
additional storm development this afternoon/evening. Due in part to
appreciable convection this morning and its related airmass
influence across the Upper Midwest, uncertainty remains regarding
the evolution of midday thunderstorm clusters and their associated
severe risk this afternoon as the airmass immediately east/southeast
of this activity continues to destabilize.
A plume of richer low-level moisture (surface dewpoints in the mid
70s F) extends northward from the mid MS Valley into the upper MS
Valley. Model guidance maintains a belt of moderate southwesterly
800-650 mb flow (30-35 kt) across the MN/IA/WI vicinity with
slightly weaker flow indicated in the upper troposphere. The
resultant hodograph structure should promote more linear
configurations of storms. Models show the development of a more
southwest-northeast oriented convective band later this afternoon
across this region, which may subdue otherwise greater potential for
severe gusts (being not oriented orthogonal to the mean wind in
800-650 mb layer), given the development of a very unstable boundary
layer in areas void of convective overturning.
Scattered severe/damaging winds appear to be the primary severe
hazard but a tornado or two is possible, especially across MN into
the WI vicinity. Storms are likely to develop farther southwest
along the front in NE but weaker shear with south extent will limit
the overall convective organization. However, severe gusts will
probably occur with the more intense cores and surges with a linear
band of storms through the evening before this activity gradually
weakens.
...Northern/Central High Plains...
No change was made to this portion of the outlook. A
moist/post-frontal environment will favor scattered storm
development later this afternoon. Relatively long/straight
hodographs at mid/upper levels from the Black Hills into northeast
WY will promote supercell development with the stronger updrafts.
Large hail and severe gusts will be the primary hazards. Farther
south, weaker flow will result in less organized storm modes, but
isolated severe gusts/hail may occur with the stronger storms
through early-mid evening.
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