SPC AC 281631
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1131 AM CDT Sun Jun 28 2026
Valid 281630Z - 291200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHERN PLAINS...CAROLINAS...AND A PART OF THE MIDWEST...
...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.
...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.
..Guyer/Supinie.. 06/28/2026
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
SPC AC 281658
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1158 AM CDT Sun Jun 28 2026
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN AND CENTRAL PLAINS AND UPPER MIDWEST...
...SUMMARY...
Severe thunderstorms are possible from parts of the central/northern
Plains into the Upper Midwest on Monday. Large hail and severe winds
are the primary concerns, though a couple of tornadoes may also
occur.
...Synopsis...
An upper low and attendant shortwave trough, initially over the
northern Rockies, will eject east/northeast across the northern
Plains on Monday. This will bring a belt of enhanced mid/upper
south/southwesterly flow across parts of the northern/central Plains
to the Upper Midwest. At the surface, low pressure will deepen over
SD and lift north/northeast through evening. A trailing cold
front/dryline will move across the Dakotas and portions of NE after
00z while a warm front lifts northward across parts of eastern ND
and northern MN through the day. A secondary lee surface low will
develop over the central High Plains, with a dryline extending
south/southwest across western KS into southwest TX.
...Dakotas/Mid-MO Valley/Upper Midwest...
Uncertainty over mesoscale details persists this forecast cycle,
though overall model guidance continues to show better agreement.
Convection appears likely to be ongoing Monday morning across the
central Dakotas near the deepening surface low and northward
extending frontal occlusion. This activity may be elevated, but
supercell wind profiles are evident in forecast soundings with
elongated/straight hodographs noted amid 50+ kt effective shear
magnitudes. A plume of steep midlevel lapse rates will be in place
across the region and elevated convection will pose a risk for large
to very large hail early in the day as storms move northward.
A very moist and unstable airmass will reside across the region,
with strong to extreme instability depicted in forecast guidance.
Convective evolution is uncertain. The extent of morning convection
could augment the northward extent of the richer boundary layer
moisture and instability. Guidance also varies in regards to the
evolution of the surface low, with some guidance being slower and
other solutions much faster. Nevertheless, the surface low/triple
point, warm front, and surface tough/cold front will be areas for
concern for convective development during the day and into the
afternoon. If supercells can develop and be surface-based near the
warm front, an all-hazards severe risk is evident given the very
favorable thermodynamic and kinematic parameter space. While initial
supercells are possible during the evening along the cold front from
the Mid-MO Valley into southern MN, boundary-parallel deep-layer
flow and an intensifying low-level jet could result in rapid upscale
growth into a bowing segment during the nighttime hours. This could
result in an increase in damaging wind potential if nighttime
convection can be near-surface based.
...KS/OK/TX...
Isolated to scattered high-based thunderstorms are likely during the
evening along the dryline. Instability and vertical shear will be
modest, limiting longevity of stronger updrafts. Nevertheless, a
deeply mixed boundary layer with inverted-v sub-cloud thermodynamic
profiles could support strong outflow gusts. Overall severe
potential appears limited, precluding marginal probabilities at this
time.
...Southeast...
Moderate instability will develop amid a seasonally moist airmass
near the Savannah River into GA Monday afternoon/early evening. A
backdoor/wedge front is expected to push south/southwest across SC
and may contribute to isolated to scattered thunderstorm development
by peak heating within a deep-layer northwesterly flow regime.
Vertical shear will be weak, but occasional sub-severe gusty
outflows will be possible, mainly across central/southern GA.
..Leitman.. 06/28/2026
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 280730
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sun Jun 28 2026
Valid 301200Z - 011200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS INTO THE UPPER MIDWEST...
...SUMMARY...
Severe thunderstorms will be possible from parts of the central High
Plains into the Upper Midwest on Tuesday.
...Upper Midwest...
Though the primary shortwave trough will be lifting into Canada, a
remnant cold front will be situated across parts of northern
Wisconsin into Minnesota. Strong to extreme buoyancy will be present
south of this boundary. A belt of moderate mid-level flow will
promote 40-45 kt of effective shear within the warm sector.
Mid-level ascent will generally be weak. Where convection can
initiate on the mesoscale, damaging winds and large hail may occur.
There is some potential that an MCS could develop given the
substantial buoyancy, but it is not clear where the preferred
corridor for that will be at this time.
...Northeast Colorado into southwest Nebraska...
A modest shortwave trough will move into the central Rockies. A
surface low is expected to develop in eastern Colorado. This will
draw low-level moisture into parts of the High Plains. Given around
40 kt of effective shear, supercells capable of large hail and
severe gusts would be possible. Low-level shear will also be
enhanced near the surface low and a tornado or two could also occur.
...Northeast...
Given the upper-level pattern, strong convection could be occurring
in Canada and move southeastward around the upper ridge. Depending
on the timing/intensity of this potential activity, severe
probabilities may be needed in future outlooks. Confidence remains
low at this time, however.
..Wendt.. 06/28/2026
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1930Z
|
