RSS Mesoscale Discussions from Storm Prediction Center
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Jun 28 2026
Valid 282000Z - 291200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS AND THE CAROLINAS...
...SUMMARY...
Severe thunderstorms are expected mainly tonight across the Dakotas.
Large to very large hail and severe winds are the primary hazards.
Thunderstorms capable of scattered wind damage are possible in parts
of the Carolinas.
...20Z Update...
The SLGT risk in eastern IA was removed, given recent convective
trends and displacement from the parent/weakening MCV. The MRGL risk
in the wake of this activity was also trimmed in parts of the
Midwest, where robust capping at the base of the EML will limit
thunderstorm/severe potential.
Farther west, the SLGT risk in the northern Plains was expanded
slightly southwestward in southwest SD, where steepening midlevel
lapse rates and around 60 kt of effective shear will promote large
hail with intensifying elevated supercells overnight.
..Weinman.. 06/28/2026
.PREV DISCUSSION... /ISSUED 1131 AM CDT Sun Jun 28 2026/
...Dakotas/northern Plains...
A belt of south-southwesterly mid-level flow near 50 kt will be
maintained from Colorado to the Dakotas, east of the broad closed
low over the northern Great Basin/Rockies. A separate lee cyclone
is expected to form in the vicinity of northeast Colorado this
afternoon and then progress northeastward across Nebraska/South
Dakota overnight.
A few storms will be possible in North Dakota during the afternoon
with perhaps an isolated severe risk developing, but the primary
regional severe risk is expected tonight. Much of the severe threat
will likely focus after dark immediately north of the lee cyclone
into South Dakota as low-level moisture steadily spreads
west-northwestward. This increasing moisture and forcing for ascent
preceding the surface cyclone (and subtle embedded speed maxima
aloft) will likely support thunderstorm development overnight across
western South Dakota into southern North Dakota. The environment
will favor supercells, which will tend to be elevated, and small
thunderstorm clusters capable of large to very large hail and severe
wind gusts.
...Upper Mississippi Valley...
A bowing cluster has weakened and tended to grow downscale this
morning but otherwise persists across eastern Iowa at midday. Some
redevelopment/re-intensification could occur on the cluster's
southern periphery near a warm front. However, this is highly
uncertain given the increasing mid-level capping/EML advection the
remainder of the night.
Later tonight, a zone of low-level warm advection will be focused
across Wisconsin along the northeast edge of the warm elevated mixed
layer. Sufficient moistening above the surface and large CAPE will
favor the potential for at least isolated large hail/strong gusts
with mostly elevated storms tonight.
...Carolinas and far southern Virginia this afternoon/evening...
A convectively augmented mid-level disturbance over the southern
Appalachians will move southeastward into the Piedmont by this
afternoon. An airmass sampled by area 12 UTC raobs (PW near 2
inches) will heat/destabilize to the south of a patch of clouds that
are more prevalent over western North Carolina. Steepening low-level
lapse rates and a belt of slightly stronger westerly 3-6 km flow (30
kt) may act to loosely organize cold pools of developing
thunderstorm clusters. Isolated to scattered wind damage (50-60 mph
gusts) will be the primary hazard with the more intense water-loaded
thunderstorm cores until around sunset.
...West Texas late this afternoon/evening...
Strong surface heating and deep mixing along a sharpening dryline
will allow high-based thunderstorm development from late afternoon
through late evening. Flow aloft will be weak, but inverted-V
profiles will yield isolated severe outflow gusts of 60-75 mph.
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SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0209 PM CDT Sun Jun 28 2026
Valid 301200Z - 011200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS TO THE UPPER GREAT LAKES...AND ACROSS PARTS OF THE
NORTHEAST...
...SUMMARY...
Severe thunderstorms will be possible from parts of the central High
Plains into the Upper Midwest, and across parts of the Northeast on
Tuesday.
...Mid-MO Valley to Upper Great Lakes...
A compact upper low and attendant shortwave trough will be located
over the Canadian Prairies into the Upper Midwest Tuesday morning.
This system will progress east/northeast through the day. While
large-scale ascent will increasing be focused north of the
international border, stronger southwesterly deep-layer flow will
persist for most of the day before weakening by evening. At the
surface, a stalled surface front will be oriented from northeast MN
into southeast SD/northern NE. Convection may be ongoing near this
boundary somewhere in MN or perhaps northern WI/Michigan Upper
Peninsula vicinity. A very moist airmass will be in place and strong
to extreme instability is forecast through the day across portions
of the region. If organized storms can develop, a risk for damaging
winds and hail is possible - particularly if upscale development
into a bowing segment occurs. Overall the forecast remains uncertain
and any corridors of greater severe potential will be heavily
influenced by remnant convection from the Day 2/Monday period and
mesoscale impacts thereof.
...CO/KS/NE/SD...
An upper shortwave impulse initially over the Great Basin early
Tuesday will eject eastward across the central Rockies and into the
adjacent High Plains during the evening/overnight hours. As this
occurs, a lee surface low will develop. Increasing
south/southeasterly low-level flow will transport modest boundary
layer moisture north and west. Isolated storms may develop near the
lee low and surface trough across eastern CO into western KS and
northeastward across western NE into southern SD along the remnant
cold front/effective warm front extending west to east near the
NE/SD border. Damaging winds and hail are possible with this
activity, though storm coverage and mesoscale details remain
uncertain.
...Northeast...
Most forecast guidance suggest storms will develop southeast across
the region from Canada within a mid/upper-level northwesterly flow
regime on the eastern periphery of an upper ridge. A very moist
airmass will support a corridor of moderate to strong instability,
though the north and eastward extent of stronger instability is
uncertain. Forecast soundings indicated 25-35 kt effective shear
magnitudes, and isolated supercells will be possible. If sufficient
clustering or outflow consolidation occurs, a forward propagating
band of storms also is possible. Damaging wind gusts will be the
primary hazard, though isolated hail or even a tornado also will be
possible depending on storm mode and evolution. If confidence
increases in a corridor of greater severe potential higher
probabilities may be needed in subsequent outlooks.
..Leitman.. 06/28/2026
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