RSS Mesoscale Discussions from Storm Prediction Center
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1150 AM CDT Tue Jun 30 2026
Valid 301630Z - 011200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
CENTRAL HIGH PLAINS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
PLAINS...GREAT LAKES AND NORTHEAST...
...SUMMARY...
Scattered severe thunderstorms are expected across parts of the
central High Plains, with severe wind gusts (60 to 85 mph) being the
primary hazard during the late afternoon and evening. Other severe
thunderstorms are expected across the Great Lakes and Northeast, as
well as broader parts of the central Plains to middle Missouri
Valley.
...Southern/Central Plains...
Scattered thunderstorms are forecast later this afternoon over the
High Plains on the western rim of richer low-level moisture and
strong insolation. Model guidance shows considerable erosion of the
capping layer by mid-afternoon with MLCAPE ranging from 1500 J/kg
over the Texas South Plains to 3500 J/kg over western Kansas.
Initially higher-based convection will gradually move east into
richer moisture and promote larger thunderstorm cores and increased
potential for storm clusters to develop. Large hail will be possible
with any initial supercell activity (i.e., most probable from the
northern Texas Panhandle into Kansas; 25-40 kt effective shear).
However, very steep surface to 300-mb lapse rates will favor strong
evaporative cooling with the more intense cores. Ample deep-layer
shear will exist for organized storms, but veering/backing of flow
with height will aid in storm outflow aggregating as linear clusters
become the primary storm mode with time. These organized but linear
clusters will likely be efficient in promoting severe wind gusts
(60-85 mph) during the early evening, coincident with a
strengthening LLJ and WAA before this threat wanes by late evening.
Weaker deep-layer shear farther south in the southern High Plains
will likely limit both storm organization and overall coverage of
the wind risk.
Later into this evening, confidence has increased in mainly
nocturnal development in a post-frontal environment, that will
probably have its genesis by early evening in the vicinity of
northeast Colorado/southwest Nebraska. These storms will likely
increase/expand northeastward tonight with large hail and damaging
wind potential, which could actually increase and become somewhat
more prominent overnight across northern Nebraska/southeast South
Dakota and neighboring Siouxland as storms cluster and as the warm
front quickly shifts northward regionally.
...Upper Midwest/Great Lakes...
A few strong storms could occur early this afternoon across northern
Michigan, but primary concern is the potential for redevelopment
later today, potentially focused along a zone of modifying
outflow/differential heating, with robust instability to the south.
Although the degree of mid-level capping is a key uncertainty, where
storms do redevelop, ample tropospheric flow will support organized
storms, including supercells capable primarily of a hail/wind risk
and perhaps a tornado. Storms will likely become more probable and
increase this evening with at least some hail and wind potential
continuing tonight.
...Northeast States...
A cluster of storms over southeast Ontario at midday will likely
continue to progress southeastward over Lake Ontario toward northern
New York today. See Mesoscale Discussion 1396 for additional
details. These storms coincide with a 30-40 kt belt of northwesterly
mid-level flow that resides on the immediate periphery of a
gradually building upper-level ridge and associated elevated mixed
layer. Residual cloud cover, via overnight/pre-dawn decayed
convection, casts a bit of uncertainty regarding boundary layer
destabilization over portions of this region, especially with
northeastward extent. Nonetheless, increasing storm
coverage/intensity is expected this afternoon including
clusters/bowing segments and possibly a few supercells.
...Southeast...
Located to the south of an upper high centered over the Tennessee
Valley, a very moist air mass is present across much of the region.
Strong heating will yield moderate buoyancy by early afternoon.
Forecast soundings depict around 20-kt effective shear which will
aid in minor multicellular organization. Localized 50-60 mph gusts
capable of isolated wind damage will accompany the stronger storms.
..Guyer/Bentley.. 06/30/2026
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SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 PM CDT Tue Jun 30 2026
Valid 011200Z - 021200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN
MINNESOTA INTO PARTS OF NORTHERN/CENTRAL WISCONSIN AND NORTHERN
LOWER MICHIGAN...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHEAST AND THE CENTRAL HIGH PLAINS...
...SUMMARY...
Scattered severe storms will again be possible across the Upper
Midwest/Great Lakes Wednesday into Wednesday night. Damaging wind
gusts (some to 80 mph) are expected, in addition to isolated large
to very large hail and a few tornadoes. Additional severe storms,
posing mainly a damaging wind risk, are possible across parts of the
Northeast and the central High Plains.
...Synopsis...
An upper shortwave trough will move across the Upper Midwest and
Great Lakes Wednesday, eventually flattening the upper ridge over
the Northeast late in the period. With this shortwave, a band of
enhanced mid/upper-level southwesterly flow will overspread the
Upper Midwest and Great Lakes. A quasi-stationary surface boundary
will extend from eastern SD northeast toward Lake Superior. Along
and south of this boundary will be a focus for potentially multiple
rounds of severe thunderstorms Wednesday and Wednesday night across
the Upper MS Valley/Great Lakes. Additional strong to severe storms
are expected across the Northeast, the South, the central/southern
High Plains, and portions of Montana.
...Upper Midwest/Great Lakes vicinity...
A somewhat similar pattern compared to previous days is expected on
Wednesday. However, the upper trough moving across the region will
be a bit strong as the upper low over the Canadian Prairies finally
becomes more progressive. A belt of 50-70 kt southwesterly flow
between 700-500 mb is noted in various forecast guidance, supporting
40+ kt effective shear magnitudes and supercell wind profiles. The
boundary layer continues to be very moist, with dewpoints in the mid
60s to mid 70s present beneath modestly steep midlevel lapse rates,
resulting in strong to extreme buoyancy.
Convection may be ongoing early in the period near southern MN,
though where exactly these storms are located depends on convective
evolution in the current Day 1/Tuesday period. This convection could
be severe with a risk for damaging winds and hail. It is possible
this activity could develop east/northeast along the surface
boundary and intensify through the morning/afternoon as it moves
across WI and pose a severe risk of damaging winds. Or, it could
weaken and additional severe storms could develop near the surface
boundary across WI/northern MI during the day. Another round of
convection is expected to develop during the evening across southern
MN. This activity could initially be supercells, with an
accompanying all-hazards severe risk. However, storms are expected
to quickly grow upscale into a bowing MCS, moving east/northeast
through the nighttime hours across WI/MI.
While exact convective evolution is uncertain, it does appear that
more than one round of severe storms is possible across the region
on Wednesday. Swaths of damaging winds (some to near 80 mph) appear
likely. Isolated large to very large hail also is possible,
especially if any supercell storm mode can persist. A few tornadoes
also will be possible.
...Northeast...
Enhanced west/northwesterly flow will continue on Wednesday across
the region. Another day of very moist and hot conditions is
expected, supporting a corridor of strong to extreme buoyancy.
Thunderstorm clusters posing a damaging wind and isolated hail risk
will be possible during the afternoon. More organized convection is
expected to sweep across the region during the evening/overnight
hours as the upper ridge breaks down with the approach of an upper
shortwave trough over the Upper Great Lakes. Organized convection
over Ontario/Quebec will likely move east/southeast during the
nighttime hours and pose a risk for damaging wind gusts.
...Central/Southern High Plains...
Convection is expected to develop along a surface dryline Wednesday
afternoon/evening. Vertically veering wind profiles will increase
southwesterly flow aloft will support transient supercell structures
initially. Forecast hodographs show 25 kt effective shear magnitudes
amid long/straight hodographs. Strong/severe outflow winds will be
possible, along with isolated hail. Sufficient clustering/outflow
consolidation may occur, supporting greater wind potential,
particularly across the western KS vicinity.
...Lower MS/TN Valleys vicinity...
A similar pattern will exist across the region on Wednesday on the
southern periphery of the upper anticyclone over the eastern U.S.
Forecast guidance once again depicts modest midlevel
east/northeasterly flow providing support for 20-25 kt effective
shear magnitudes. Thunderstorm clusters will develop during the
afternoon within the theta-e axis. The very moist and abundantly
unstable airmass will support a wet microburst risk. If sufficient
clustering occurs, some potential for forward propagating convection
will exist, which could increase damaging wind potential through
early evening.
...MT...
An upper trough over the western U.S. will bring modestly enhanced
southwesterly mid/upper flow across portions of the northern Rockies
Wednesday afternoon/evening. A plume of steeper midlevel lapse rates
will gradually spread northeast from the Great Basin into parts of
southwest/central MT atop modest low-level moisture. This will
support 500-1000 J/kg MLCAPE. Steep low-level lapse rates and
sufficient vertical shear for organized cells/clusters will result
in a risk for isolated strong to severe wind gusts.
..Leitman.. 06/30/2026
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