Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Wed Aug 27 2025
Valid 271630Z - 281200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL HIGH PLAINS AND UPPER MIDWEST...
...SUMMARY...
Isolated strong to severe thunderstorms may occur across parts of
the central High Plains and Upper Midwest this afternoon and early
evening.
...Central High Plains...
Upper ridging should remain suppressed over TX today, with modest
mid-level westerly flow persisting across the central Plains. Late
morning visible satellite imagery shows some clearing across eastern
CO, which should aid in diurnal destabilization this afternoon.
Gradual low-level moisture return is forecast to continue today
across the central High Plains, generally along and east of a weak
lee trough/low where low to mid 60s surface dewpoints are present.
With scattered to numerous thunderstorms over much of the Southwest
and southern/central Rockies yesterday, there is not a notable EML
present over the central High Plains today (reference 12Z observed
DDC sounding). This should temper the degree of instability that can
develop through the afternoon to some extent. Even so, around
500-1500 J/kg of MLCAPE appears plausible with additional diurnal
heating of the modestly moistened low-level airmass.
Weak low-level southerly flow will veer to westerly and gradually
strengthen with height through mid/upper levels, supporting around
25-40 kt of deep-layer shear. Thunderstorms are expected to develop
initially along/near the Front Range this afternoon, before
spreading slowly east-southeastward across eastern CO and parts of
western KS through the evening. Isolated severe hail may occur with
the strongest cores/marginal supercell structures, until gradual
outflow/cold pool amalgamation encourages one or more clusters with
a greater threat for occasional strong to severe gusts. Based on
latest observational and short-term guidance trends, the Marginal
Risk has been expanded to include more of eastern CO and western KS.
Mainly elevated thunderstorms will likely continue overnight into
central/eastern KS in a modest low-level warm advection regime.
However, confidence in a continued hail/wind threat with this
activity remains low at this time.
...Upper Midwest...
On the western side of a large-scale upper trough over eastern
Canada and the Atlantic Coast states, modestly enhanced
northwesterly mid-level flow is forecast to persist through much of
the period. A weak embedded shortwave trough moving across southern
MN and vicinity late this morning suggests modest large-scale
subsidence in its wake. This casts some uncertainty on the possible
development of isolated to scattered thunderstorms later today
along/south of a weak surface trough across eastern SD into
central/southern MN. Even so, most guidance suggests at least
isolated thunderstorms will form across this region by late
afternoon/early evening. Cool mid-level temperatures and generally
long/straight hodographs aloft suggest some threat for severe hail
with any of the stronger cores that can be sustained. Have therefore
added a focused Marginal Risk across parts of eastern SD into
southern MN for this potential.
..Gleason/Moore.. 08/27/2025
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