SPC Jul 27, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0800 AM CDT Mon Jul 27 2026

Valid 271300Z - 281200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDWEST/LAKE MICHIGAN VICINITY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL
HIGH PLAINS...

...SUMMARY...
Severe storms capable of strong to severe wind gusts and large hail
are expected across the Great Lakes and Midwest through tonight.
More sporadic occurrences of damaging wind are possible in the
Mid-Atlantic, Tennessee Valley, central High Plains, and southeast
Arizona.

...Midwest/Great Lakes to the Ohio/Tennessee Valleys...
A complex forecast scenario again exists today complicated by
numerous mesoscale factors and well-above-normal short-term guidance
variability. There nonetheless is an appreciable broad regional
severe potential, at least conditionally, attributable to robust or
even extreme source-region buoyancy and an appreciable belt of
northwesterly flow aloft (50+ kt at 500 mb), which could easily
support well-organized wind-producing swaths regionally into the
afternoon and tonight.

A high-moisture-content airmass is prevalent regionally to the south
of a cold front that extends across South Dakota/Minnesota toward
Lake Superior. Several corridors of storms are ongoing early this
morning, including across the western Upper Peninsula of
Michigan/far northern Wisconsin, as well as southwest lower
Michigan, with some uptick in ACCAS/mid-level convection in the
predawn hours across eastern Iowa/far southwest Wisconsin.
Increasing daytime storms, in terms of coverage/intensity/
organization, may stem from, but are not limited to, these early day
corridors. Bouts of large hail will be possible given the degree of
vertical shear/buoyancy, and some tornado risk could exist, but the
most prominent concern would be for damaging wind potential,
particularly if one or more south/southeast-moving
forward-propagating clusters emerge, which currently appear most
probable this afternoon and tonight across eastern Wisconsin/western
Michigan and Lake Michigan vicinity southeastward into Indiana,
western Ohio, and Illinois.

...Central High Plains...
Moist, post-frontal surface flow is expected across much of
Nebraska/South Dakota, shifting from northerly early in the day to
more easterly by the afternoon. Dewpoints will initially be in the
mid to upper 70s F, although strong boundary-layer mixing will
likely result in dewpoints ranging from the upper 50s/low 60s across
the Nebraska Panhandle to the low 70s across eastern Nebraska. This
reservoir of low-level moisture coupled with strong heating and
steep mid-level lapse rates will result in a corridor of moderate to
extreme buoyancy from eastern Wyoming/northeast Colorado/southwest
South Dakota eastward across south-central
South Dakota and much of Nebraska.

Most of the guidance indicates a subtle, convectively augmented
vorticity maximum will progress eastward through the northern
periphery of the Four Corner upper ridge. This should contribute to
thunderstorm development across the high terrain, which would then
progress downstream into a more moist and unstable airmass. One or
more clusters could evolve, but the overall predictability of the
convective evolution is low. That said, environmental conditions
support the potential for strong to severe gusts, including the
potential for some over 75 mph.

...Mid-Atlantic States/Delmarva...
Isolated damaging wind potential will exist during the
afternoon/evening, especially near/east of I-95 in vicinity of a
surface trough, where marginal buoyancy and deep-layer shear could
support a few stronger updrafts/downdrafts.

...Southeast Arizona...
Isolated severe-caliber wind gusts are possible over southeast
Arizona as mid-level moisture and diurnal heating leads to scattered
storms over the higher terrain. Cells are expected to move westward
into warmer temperatures and deeper boundary-layer mixing, with PWAT
over 1.25" and steep low-level lapse rates supporting strong
convective outflows.

..Guyer/Wendt.. 07/27/2026


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SPC Jul 27, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0802 PM CDT Sun Jul 26 2026

Valid 270100Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS 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 evening and tonight.

...Upper Midwest...
A very unstable environment remains in place across the region, with
the MPX, GRB, and DVN 00Z soundings sampling MLCAPE from 3100, 2900,
and 2800 J/kg, respectively. Surface observations show mid to upper
70s dewpoints on the warm side of the warm front extending from
north-central MN through northeast WI/far western Upper MI. A
thunderstorm has matured upstream of this corridor, with the
expectation it will remain strong to severe as it continues
southeastward. Modest low-level warm advection into this boundary
will also contribute to additional thunderstorms this evening and
overnight. Environmental conditions are still expected to support
large to very large hail early in the convective cycle while a more
cellular mode is likely. Thereafter, a trend towards bowing segments
capable of severe wind gusts is anticipated. A singular MCS could
eventually develop, with severe gusts possible as it moves southward
as well. Some gusts, both within the line segments and early in the
MCS lifecycle, could be significant (i.e. over 75 mph).

...TN Valley...
A cold-pool-driven MCS continues to propagate south-southeast at
approximately 40 kts. The downstream airmass is very moist, with
numerous sites reporting dewpoints in the low 80s. This moisture is
contributing to extreme buoyancy, with the recent 00Z BNA sounding
sampling 4500 J/kg of SBCAPE. This MCS is also oriented
perpendicular to the deep-layer vertical shear. All of these factors
will contribute to continued southward progression, with an
attendant risk for strong gusts likely extending into Middle TN this
evening.

...South-Central into Southeast SD into central NE...
Numerous attempts at deep convection along the weak surface trough
extending from south-central SD through central NE have failed thus
far. The window of opportunity for deep convection will likely
remain open for the next hour or two before building inhibition
associated with nocturnal cooling precludes mature convection. Until
that occurs, there remains a conditional risk for severe
thunderstorms capable of strong downdrafts and isolated large hail.

...Elsewhere...
Increasing thunderstorm coverage is possible across the Mid-Atlantic
over the next few hours as a shortwave trough progresses
southeastward across the region. Moderate vertical shear could
support updraft organization with deeper, more persistent
convection. Isolated damaging gusts and hail are possible with the
more organized storms. Isolated damaging gusts remain possible
across northern Wyoming and far southwest South Dakota as high-based
thunderstorms track northeastward across the region this evening.
Jackson Hole Wyoming reported a gust of 50 kt at 2353Z.

..Mosier.. 07/27/2026


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SPC Jul 26, 2026 2000 UTC Day 1 Convective Outlook

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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SPC Jul 26, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1110 AM CDT Sun Jul 26 2026

Valid 261630Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
UPPER MIDWEST/GREAT LAKES...

...SUMMARY...
Severe thunderstorms capable of large to very large hail, damaging
winds (possibly 75+ mph), and tornado risk are expected from the
upper Mississippi Valley and Great Lakes southwestward into
Nebraska, mainly this afternoon and tonight.

...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.

..Leitman.. 07/26/2026


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