ACUS02 KWNS 270557
SWODY2
SPC AC 270555

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 AM CDT Sun Jul 27 2025

Valid 281200Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL/EASTERN
SOUTH DAKOTA...FAR SOUTHWEST MINNESOTA...FAR NORTHWEST IOWA...

...SUMMARY...
Severe thunderstorms are possible from the northern Rockies into the
Dakotas and Upper Midwest Monday afternoon and evening.

...Synopsis...
Strong mid-level flow will continue in the northern Plains along the
crest of the upper ridge in the central CONUS. More modest mid-level
winds will also extend westward into the northern Rockies and
portions of the northern Great Basin. At the surface, a cold front
will be positioned from northern Rockies into the northern Plains. A
surface low will deepen in South Dakota/Nebraska. A theta-e
boundary/pseudo warm front will extend from the low into Minnesota
Wisconsin. A few subtle shortwaves are expected to move into the
northern Plains as they progress along the periphery of the upper ridge.

...South Dakota into Upper Mississippi Valley...
While the forecast remains complex and there are still some
uncertainties to be resolved, there is sufficient confidence in
storm development and coverage in parts of central/eastern South
Dakota to increase severe probabilities. Strong heating to the west
of the surface trough/low, the southward advancing cold front, and
subtle lift from mid-level shortwave troughs suggest storm
development is more probable than not. Both CAMs as well as
mesoscale/global models show signals for this scenario. There is
still some potential for storms to develop farther northwest in
southeastern Montana and progress along the boundary into greater
buoyancy, but this solution is rather uncertain. There is additional
uncertainty as to how far east a greater severe threat will extend.
The NAM/ECMWF/GFS and a couple of CAMs show an MCS moving through
central/southern Minnesota late Sunday into Monday morning. Given
the unknown amount of airmass recovery that will occur in this area,
Marginal risk probabilities will remain.

Strong to extreme buoyancy is expected (3000-4000+ J/kg MLCAPE)
south of the cold front. With 35-50 kts of effective shear, storms
will be organized. Initial development near the surface low will
likely be supercellular for a period, though a couple of brief
supercells could also occur along the cold front. These storms would
bring the greatest risk for hail and perhaps a tornado. With some
larger temperature-dewpoint spreads at the surface, along with
boundary-parallel shear and eventual southward movement of the
front, upscale growth will likely occur fairly quickly in the
convective cycle. Potential exists for a severe MCS to develop and
move along the boundary. A swath of severe gusts would be possible
should this occur.

...Montana into western Dakotas...
Modest surface moisture will be pushed into the northern Rockies.
Storm development is likely within parts of central Montana over the
terrain. With cool temperatures aloft, MLCAPE of around 1000 J/kg is
possible during the afternoon. Effective shear will be near 30 kts
farther west but will increase with eastward extent. A well-mixed
boundary layer will promote severe wind potential, though isolated
marginal hail could occur with the stronger storms.

In eastern Montana, a weak surface trough intersecting with the cold
front may serve as a focus for convective development during the
early afternoon. Storms would likely be outflow dominant with a
primary hazard of severe wind gusts. The question will be whether a
more organized cluster can evolve out of this activity and progress
southeastward along the boundary. Confidence is too low in this
particular outcome to increase severe probabilities.

...Lower Ohio Valley into Mid-South...
There is a conditional risk for marginally organized storm clusters
associated with an MCV from Sunday convection in the Upper Midwest.
Given the uncertain position and intensity of the MCV, highlights
will be withheld at this juncture.

..Wendt.. 07/27/2025

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