LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0304 PM CDT Sun Jul 26 2026
Valid 262000Z - 271200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF THE UPPER MIDWEST AND WESTERN GREAT LAKES....
...SUMMARY...
Severe thunderstorms capable of large to very large hail, damaging
winds (possibly 75+ mph), and tornado risk remain likely from the
upper Mississippi Valley and Great Lakes southwestward into
Nebraska, mainly late this afternoon and tonight.
...20Z Update Upper Midwest...
No changes were made to the prior outlook. Severe storm development
remains likely this afternoon and evening as a very warm air mass
continues to destabilize. Weak, but sufficient, synoptic ascent
(evident in visible imagery) should aid in removing inhibition by
late this afternoon. Initial supercells developing over northeastern
MN and far northern WI will pose an all-hazards risk, including
locally severe wind gusts, very large hail, and a couple of
tornadoes. An MCS should eventually develop and track
south/southeast across WI and MI with a risk for damaging gusts and
a brief tornado or two through tonight.
...NE...
More isolated higher-based convection remains possible from central
and eastern NE, into western IA, and southeast SD late this
afternoon and evening. Very hot surface temperatures and moderate
buoyancy will support a few stronger storms with damaging wind and
isolated hail potential. Convective development appears most
probable along a thermally induced surface pressure trough, from
central NE northeastward late this afternoon.
...Mid MS Valley...
A very unstable and weakly capped air mass is present along a
diffuse differential heating zone from northwest IL, into northern
TN. Current expectations are for one or more clusters of
thunderstorms to develop along the boundary and ahead of a weak
mid-level wave/MCV across IA/IL, before spreading
south/southeastward into this evening. The extreme instability
(4000+ J/kg MLCAPE) and 25-35 kt of deep-layer shear should support
organized clusters, and eventually an MCS, with damaging winds
likely. A tornado or two is also possible with initial convection
along the boundary owing to extreme buoyancy, or any embedded QLCS
circulations with the expected MCS. See MCD#1742 for short-term
information.
Elsewhere, isolated damaging gusts remain possible with scattered
thunderstorms over the northern Rockies and across the Mid
Atlantic/Southeast. Weaker buoyancy/shear overlap suggests these
occurrences will be more sporadic, with limited storm
organization/longevity. See the prior discussion for additional
information.
..Lyons.. 07/26/2026
.PREV DISCUSSION... /ISSUED 1110 AM CDT Sun Jul 26 2026/
...Upper Midwest/Great Lakes...
Initial supercell storms are expected to develop across northern
MN/WI later this afternoon, aided by a favorably timed shortwave
impulse rounding the Plains upper ridge. Another MCV/shortwave
impulse located over the Dakotas at midday will also spread
east/southeast across southern/central MN this afternoon. These
features will provide support for one or more focused areas of
thunderstorm development. Initial supercells will pose an
all-hazards risk, including locally severe wind gusts, very large
hail, and a couple of tornadoes. With time into the evening, initial
supercells may grow into one or two small bowing MCSs. This storm
mode transition will support an increased risk for intense damaging
wind swaths this evening into tonight as convection spreads
southeast along a strong instability/moisture gradient across WI and
the Lake Michigan vicinity.
...Mid-Mississippi/Lower Ohio/Tennessee Valleys...
Multiple areas of strong to severe storms will be possible this
afternoon into tonight from near the MS River into IL/IN/KY/TN.
Thunderstorm development may be aided by a weak shortwave
impulse/MCV migrating southeast from IA at midday and into the Lower
OH Valley this evening. Storms are expected to develop along a
corridor of differential heating near/just east of the MS River
where mostly clear skies this morning have already resulted in
temperatures approaching 85-90 F, while scattered clouds further
east will maintain somewhat lower high temperatures. Thunderstorm
clusters this afternoon will pose a risk for severe/damaging wind
gusts. Sufficient clustering may occur and some upscale development
into a forward propagating bow may occur across the Lower Ohio
Valley vicinity this evening, and wind probabilities have been
increased to 30 percent for parts of southern IL/IN and western KY.
This activity could be maintained southward during the overnight
hours as far south as northern AL/GA given favorable instability and
sufficiently strong northwesterly flow aloft. Damaging wind gusts
could persist with this activity as it spreads south/southeast
across TN into AL/GA toward early Monday morning.
...NE/SD/IA...
A deeply mixed and hot boundary layer will develop this
afternoon/early evening in the vicinity of a weak surface trough
from NE into southeast SD/northwest IA. Very steep lapse rates aloft
will foster 1500-2000 J/kg MLCAPE. Vertically veering wind profiles
and increasing northwesterly flow aloft will provide 25-35 kt
effective shear magnitudes and a few organized cells/clusters may
develop by late afternoon. Damaging wind gusts of 60-80 mph would be
the main hazard with this activity. While temperatures are somewhat
warm aloft, the strongest storms could produce sporadic large hail.
...Mid-Atlantic/Carolinas/Southeast GA/Northern FL...
Upper troughing will persist today across the East, though some
enhancement to northwesterly flow aloft is expected. Relatively cool
conditions, weak lapse rates, and the potential influence of smoke
will temper destabilization across the Mid-Atlantic. Nevertheless,
MLCAPE 1000 J/kg amid 25-35 kt of effective shear may support
occasional organized storms capable of producing locally damaging
gusts.
Stronger heating/destabilization is expected farther south across
the Carolinas into GA/FL. Deep-layer flow/shear will be somewhat
weaker compared to farther north, but may still be sufficient for
transient storm organization with sporadic locally damaging winds
possible.
...Southeast MT/northern WY/Black Hills vicinity...
High-based convection is expected to develop this afternoon along
the northern periphery of the upper ridge, with the greatest storm
coverage expected across parts of northern Wyoming and southern
Montana. Overall buoyancy is expected to remain weak, but inverted-v
profiles will support a threat of strong to localized severe gusts
as storms spread eastward toward the Black Hills before weakening
into mid/late evening.
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