RSS Mesoscale Discussions from Storm Prediction Center
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1118 AM CDT Fri Aug 08 2025
Valid 081630Z - 091200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
TONIGHT OVER PARTS THE UPPER MIDWEST....
...SUMMARY...
Scattered severe thunderstorms are possible this evening and
tonight across parts of the Upper Midwest. Scattered damaging winds,
large hail, and a couple tornadoes are possible.
...Upper Midwest...
The large convective complex that affected ND/MN last night has
mostly dissipated, with the associated shortwave trough lifting
across the MN Arrowhead. Shortwave ridging is occurring in the wake
of this system, which should suppress deep convective development
for most of the afternoon. Southeasterly low-level winds and
daytime heating across much of MN and eastern SD will help
re-establish a very moist/unstable air mass (MLCAPE > 4000 J/kg) by
late afternoon.
Another strong shortwave trough now over WY will begin affecting the
ND/MN area by that time, with an associated cold front approaching
the area. Scattered thunderstorms are expected to form along/ahead
of the front, mainly after 00z. Deep-layer shear will support
supercell storm structures capable of large hail and damaging wind
gusts. A few tornadoes are also possible, given the very moist
environment and backed low-level winds. However, many of the storms
may be elevated and behind the front. Activity will persist deep
into the night, spreading eastward across MN and into parts of
northern WI and western Upper MI.
..Hart/Squitieri.. 08/08/2025
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SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0241 PM CDT Fri Aug 08 2025
Valid 082000Z - 091200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING INTO
TONIGHT FOR PARTS OF THE UPPER MIDWEST AND THE CENTRAL HIGH
PLAINS...
...SUMMARY...
Scattered severe thunderstorms with damaging winds, large hail, and
a couple tornadoes are possible this evening and tonight across
parts of the Upper Midwest and the central High Plains.
...20z Update...
...Upper Midwest...
Latest radar/satellite trends show a residual storm complex and
cloud cover over northeast Minnesota. This activity continues to
diminish, with some weak convection developing in proximity. Surface
observations suggest little evidence of extensive outflow in its
wake, though southeasterly surface winds are prevalent across much
of Minnesota where cloud cover has remained persistent. To the west,
a cold front continues to advance eastward and is beginning to
impinge upon portions of northwest Minnesota into eastern South
Dakota.
Storm initiation is still expected by early evening along the cold
front in eastern South/North Dakota, with a quick transition from
cellular to linear modes. Not much has changed in terms of
expectations from the prior outlook. As this activity grows upscale
and matures, some potential for a more concentrated corridor of
damaging winds may emerge in far northeast Minnesota, but details
remain uncertain and will be reevaluated in the 01z Outlook. With
that said, given the potential for upscale growth, have expanded the
Marginal area (Level 1 of 5) eastward into portions of northeast
Iowa and vicinity.
...Southwest South Dakota/Nebraska Panhandle...
Surface observations and SPC mesoanalysis show a post-frontal
airmass with enough residual moisture to allow for modest
destabilization across the region. Recent CAM guidance suggests the
potential for isolated convection to develop in the high terrain of
eastern Wyoming and persist eastward into southwest South Dakota and
the Nebraska Panhandle. Given effective shear of 45-50 kt in
association with enhanced flow along the southern periphery of the
upper-level trough, a few supercell storms are possible with severe
hail/wind the main threats. Therefore, have introduced a Slight Risk
(Level 2 of 5) to encompass this potential.
..Karstens/Lyons.. 08/08/2025
.PREV DISCUSSION... /ISSUED 1118 AM CDT Fri Aug 08 2025/
...Upper Midwest...
The large convective complex that affected ND/MN last night has
mostly dissipated, with the associated shortwave trough lifting
across the MN Arrowhead. Shortwave ridging is occurring in the wake
of this system, which should suppress deep convective development
for most of the afternoon. Southeasterly low-level winds and
daytime heating across much of MN and eastern SD will help
re-establish a very moist/unstable air mass (MLCAPE > 4000 J/kg) by
late afternoon.
Another strong shortwave trough now over WY will begin affecting the
ND/MN area by that time, with an associated cold front approaching
the area. Scattered thunderstorms are expected to form along/ahead
of the front, mainly after 00z. Deep-layer shear will support
supercell storm structures capable of large hail and damaging wind
gusts. A few tornadoes are also possible, given the very moist
environment and backed low-level winds. However, many of the storms
may be elevated and behind the front. Activity will persist deep
into the night, spreading eastward across MN and into parts of
northern WI and western Upper MI.
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1223 PM CDT Fri Aug 08 2025
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN PARTS OF
WI/IA/IL AND CO...
...SUMMARY...
Multiple damaging wind swaths are possible from Saturday into
Saturday night, centered on central/southern Wisconsin,
central/eastern Iowa, and northwest Illinois. Multiple rounds of
large hail are possible across eastern Colorado starting in the late
afternoon.
...Upper Great Lakes to the Lower MO Valley...
A broken linear MCS should be ongoing at 12Z Saturday, centered from
western Upper MI to northern IA. Some CAMs suggest this should decay
into multiple separate clusters during the late morning, while most
maintain at least one coherent linear band eastward. Diurnal
destabilization ahead of the large-scale outflow may support
intensification by midday into the afternoon, mainly in WI. The bulk
of strong mid-level southwesterlies will be displaced to the rear of
the composite outflow/cold front as the amplified shortwave trough
over the northern Great Plains drifts east. This will yield a
pronounced gradient from northwest to southeast across the
outflow/front, and support decreasing organization as clusters reach
the Lake MI vicinity. Scattered damaging winds should be the
predominant hazard.
A broad low-level jet will nocturnally strengthen from the southern
High Plains to the Lower MO Valley. Regenerative storm development
is expected in the IA vicinity along the trailing front as it
becomes quasi-stationary and orients west/east. With ample buoyancy
lingering, modest organization into small-scale bows is possible on
Saturday night, yielding another round of damaging wind potential.
...Central/southern High Plains...
A cold front pushing south on D1 should become quasi-stationary over
the southern High Plains in the TX Panhandle tomorrow. Isolated
storms are possible near the boundary with a threat for sporadic
microbursts amid hot temperatures south of the front. Farther north
along the Front Range, a post-frontal upslope flow regime will favor
regenerative supercell development commencing by late afternoon.
With modestly enhanced mid-level westerlies atop the weak low-level
easterlies, strong deep-layer shear and adequate buoyancy will favor
a risk of large to significant severe hail centered on
east-central/southeast CO. A low-amplitude shortwave impulse
ejecting towards the southern Rockies should foster thunderstorms
persisting well into Saturday night. While buoyancy will nocturnally
weaken, isolated severe hail/wind may occur from eastern CO into
western KS.
..Grams.. 08/08/2025
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 PM CDT Fri Aug 08 2025
Valid 101200Z - 111200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTH-CENTRAL HIGH PLAINS TO THE CENTRAL GREAT LAKES...
...SUMMARY...
Isolated severe thunderstorms are possible from the south-central
High Plains to the central Great Lakes, mainly Sunday afternoon and
evening.
...South-central High Plains to the central Great Lakes...
Low severe probabilities are evident on Sunday across a large swath
of the central states along the effective baroclinic zone which will
be modulated by overnight convective regimes. These should be in a
decaying state, centered over the central High Plains and from the
Lower MO Valley to the Lake MI vicinity. Diurnal destabilization in
the wake of morning activity, especially pronounced to the south of
remnant convective outflows, should foster ample buoyancy in a swath
from the lee of the southern Rockies towards IN/Lower MI.
Low-amplitude mid-level troughing should persist across the
south-central High Plains, despite progged dampening of an embedded
shortwave impulse that should cross the southern Rockies early
Sunday. This will yield favorable deep-layer shear for supercells in
eastern CO and the Raton Mesa vicinity, supportive of isolated large
hail and severe gusts. Progressively weaker deep-layer shear is
expected with southern/eastern extent owing to a persistent
mid-level ridge from the southern High Plains to the Lower Great
Lakes. But with signals for fairly extensive afternoon to evening
storm coverage along the baroclinic zone, several clusters of mainly
weakly organized convection seem plausible. This should support a
primary threat of strong to localized severe gusts from KS to MI.
..Grams.. 08/08/2025
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