RSS Mesoscale Discussions from Storm Prediction Center
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0107 AM CDT Tue Jun 30 2026
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE
MID-MISSOURI VALLEY INTO CENTRAL WISCONSIN...
...SUMMARY...
Isolated to scattered strong to severe storms will again be possible
from the central Plains into the Upper Midwest as well the Northeast
on Wednesday. Severe wind gusts and large hail are the main
concerns.
...Mid-Missouri Valley into central Wisconsin...
Models are in general agreement that a cluster/MCS will be ongoing
in the eastern South Dakota/southern Minnesota vicinity early
Wednesday morning. There is at least some potential for damaging
surface gusts with this activity. Further intensification could also
occur as the airmass destabilizes in parts of Wisconsin into the
afternoon. However the early day activity evolves, an outflow
boundary from this activity will serve as a focus for additional
afternoon thunderstorms. 70+ F dewpoints to the south of the
boundary will again promote strong to locally extreme buoyancy.
Moderate to strong mid-level winds on the southern flank of the
upper trough in Canada will allow for 40-55 kt of effective shear
near the surface boundary. Initial supercells will be capable of
large to isolated very large (around 2-2.5 in.) hail and perhaps a
tornado or two. Given the instability, strong downdrafts will likely
lead to upscale growth relatively quickly. The risk for
severe/damaging winds will become the primary hazard with time,
particularly if an MCS can develop. A Slight Risk has been added to
cover both potential scenarios.
...Northeast...
The forecast continues to be uncertain given the nebulous forcing
for ascent. Nonetheless, substantial buoyancy will be in place
across the region (3000-5000 J/kg MLCAPE). Effective shear of 35-40
kt will promote some storm organization. Model guidance shows
variable solutions from more isolated cellular activity to a cluster
moving southeastward out of Canada. Given the low confidence in
placing more organized activity, a Marginal Risk will be maintained
for now. Damaging winds and isolated large hail will be possible.
...Central High Plains...
Thunderstorm development is expected within the lee trough during
the afternoon. A deeply-mixed boundary layer will promote potential
for severe winds especially if any clustering can occur. Shear will
be modest and severe coverage is expected to be isolated.
...Southeast...
Strong buoyancy will be in place during the afternoon given rich
moisture (70+ F dewpoints). Shear will be quite weak with some minor
enhancement in the lower Mississippi Valley. Models do show some
potential for clustering, but the location is quite variable. Lack
of even subtle features to focus convection keeps confidence in a
more organized damaging wind threat low.
..Wendt.. 06/30/2026
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0234 AM CDT Tue Jun 30 2026
Valid 021200Z - 031200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE BLACK
HILLS VICINITY INTO PARTS OF THE MIDWEST...
...SUMMARY...
Strong to severe storms will be possible from the northern Plains
into the Midwest and Great Lakes regions on Thursday. Isolated
strong to severe storms may also occur in the Tennessee
Valley/Southeast as well as parts of the Northeast.
...Synopsis...
Upper ridging will continue in the East with broad cyclonic flow in
the West. Embedded shortwave troughs will likely impact the northern
Plains. Another shortwave trough embedded within northwesterly flow
aloft will move into parts of the Northeast. A stalled surface
boundary will be present from the northern High Plains into the
Upper Midwest with a lee trough/weak surface low developing in the
High Plains.
...Black Hills into Iowa/Minnesota...
A subtle shortwave trough is evident in model guidance. This feature
will move into Wyoming/Montana and eventually the western Dakotas.
Convection appears likely to develop within the higher terrain (Big
Horns/Black Hills) and move into an airmass with increasingly rich
low-level moisture to the east. Convection should be able to
organize along the surface boundary with around 40 kt of effective
shear parallel to the boundary itself. Additional convection is also
possible along the stationary front as low-level warm advection
increases. Though there is some variability in where any eventual
MCS will propagate, there is enough confidence to include a 15%
severe probability area that encompasses the envelope of potential
tracks. The environment would support significant hail with
supercells and significant winds with an organized MCS.
...Northeast...
Ahead of a cold front attendant from a surface low in Quebec,
convection will be possible during the afternoon. The timing of the
convection, and thus the available buoyancy, is not entirely
certain. Damaging wind gusts and large hail would be possible.
...Tennessee Valley into Southeast...
A subtle easterly wave rotating around the upper anticyclone will
promote afternoon convection within a very moist and unstable
airmass. Given the mid-level lapse rates will fairly steep, storms
will likely be capable of damaging downburst winds despite weak
shear.
..Wendt.. 06/30/2026
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0338 AM CDT Tue Jun 30 2026
Valid 031200Z - 081200Z
...DISCUSSION...
Upper-level flow is expected to become more zonal across the CONUS
this Friday. The upper ridge within the East will lose amplitude and
develop westward and amplify once again into early next week. The
exact structure of the upper ridge does vary within model guidance.
At the surface, a mostly stationary boundary will continue to be
modified/reinforced by convection occurring along/near it on
preceding days. As the upper ridge builds in the West, this boundary
will likely get pushed farther south within the areas east of the
Mississippi by the developing surface high in the Upper
Midwest/Great Lakes. Moisture will then be transported farther
north/west in the Plains/High Plains beginning sometime this
weekend. The general theme for the extended forecast will be where
subtle shortwaves/MCVs will propagate and spur convection along the
boundary.
For Friday, another MCS is possible along the surface boundary
similar to D3/Thursday. Uncertainty in how Thursday's convection
will impact the location of the boundary and most favorable
environment reduces confidence on where the greatest severe threat
will be. Into the weekend and early next week, some severe threat is
possible in parts of the eastern CONUS in association with MCV from
convection in the Plains/Midwest. Additional severe storms could
occur as northwesterly flow aloft develops in the High Plains. There
are still enough differences in the upper-level pattern between
medium range guidance that predictability of any higher threat
corridors is low.
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