ACUS02 KWNS 081737
SWODY2
SPC AC 081736
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Mon Jun 08 2026
Valid 091200Z - 101200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF NORTH AND SOUTH DAKOTA INTO NORTHWEST MINNESOTA...
...SUMMARY...
Numerous severe thunderstorms are likely to develop across parts of
the northern Plains and Upper Mississippi Valley Tuesday afternoon
into night. Very large hail, tornadoes, a few of which could be
strong, and damaging winds with significant gusts appear likely.
...Synopsis...
A negatively tilted upper trough will be oriented from the Pacific
Northwest to the southern Great Basin Tuesday morning. This feature
will pivot east through the period, become positioned from southwest Saskatchewan to the central High Plains. A belt of enhanced
southwesterly 500 mb flow will overspread portions of the
northern/central Plains ahead of the aforementioned trough.
Meanwhile, an intensifying low-level jet will develop during the evening/overnight hours across much of the Plains toward the Upper
Midwest.
At the surface, low pressure over eastern MT will gradually deepen
and shift east/northeast across the northern Plains and adjacent
Canadian Prairies. A Pacific front/dryline feature will extend
southward from the low across the western Dakotas and NE. A
secondary surface low may develop in the vicinity of eastern
CO/western KS/southwest NE, where a dryline will extend from western
KS southward into northwest OK and the TX Panhandle. Further east, a
quasi-warm front feature is expected to extend northwest to
southeast from MN to the Mid-MS Valley. This boundary may gradually
lift northward through the evening/overnight in response to the
low/midlevel mass response/increasing low-level jet.
These boundaries will be a focus for severe storm development during
the afternoon into the overnight hours.
...Northern Plains vicinity...
Convection is expected to develop near the ND/MT border vicinity by
mid/late afternoon along the surface boundary. A warm front should
be well north of the Dakotas over the southern Canadian Prairies,
and increasing southerly low-level flow will transport low to mid
60s F dewpoints northward into the region. Cooling aloft will result
in steepening midlevel lapse rates atop rich boundary-layer
moisture, supporting MLCAPE increasing to 3000-4000 J/kg.
South/southwesterly low-level winds will become southwesterly in the
mid/upper levels, resulting in supercell wind profiles and 40+ kt
effective shear magnitudes. Initial supercell storms are expected,
though these storms may be somewhat higher-based within the more
modest boundary layer moisture across the western Dakotas/far
eastern MT. Large hail and damaging gusts are possible with these
storms initially.
As convection develops eastward into the axis of greater low-level
moisture and strong instability, severe potential will increase,
particularly with respect to swaths of damaging winds and tornadoes.
As the low-level jet increases during the evening, and given
mid/upper flow oriented parallel to the surface boundary, upscale
growth into one or more linear segments is expected. As cold pool
consolidation occurs, potential for significant wind gusts (greater
than 65 kt) is expected to increase across parts of central ND.
Low-level shear will also support tornado potential, whether
semi-discrete supercells can be maintained, or with mesovortex
generation within linear bands. As such, have left tornado
probabilities similar to the prior forecast. Given the expectation
that storm mode will become more linear with time, hail
probabilities have been lowered (removed 45 percent). Nevertheless,
large to very large hail will be possible with any discrete
supercells that can be maintained or are embedded within linear
segments.
...NE/SD/Mid-MO Valley vicinity...
Convection emanating northeast from NE may eventually grow upscale
into an MCS during the nighttime hours and spread into eastern SD
and the Mid-MO Valley area. This scenario is uncertain. However,
given ample deep-layer flow, extreme instability and at least subtle large-scale ascent over the region as the low-level jet overspreads
this area overnight, this scenario seems plausible. If this occurs,
damaging wind potential will be possible, and severe probabilities
have been expanded eastward across portions of the region.
...KS into the OK/TX Panhandles and northeast NM...
High-based convection is expected to develop along the surface
dryline during the late afternoon. Deep boundary layer mixing will
support steep low-level lapse rates. 500 mb temperatures around -10
C also will support steep midlevel lapse rates near 8-8.5 C/km per
regional forecast soundings. Deep layer shear will not be as strong
as further north, but strong instability and inverted-v sub-cloud
thermodynamic profiles will support severe wind gusts. There is some
potential that if storms can be maintained further east toward
better low-level moisture as the low-level jet increases during the
evening, a swath of significant wind gusts could occur across the
southwest KS vicinity. Severe probabilities have been increased
across portions of the area given a favorable environment and strong
signal within most forecast guidance.
...Mid-MS Valley into Lower OH Valley...
A quasi-warm front/moisture boundary will overlap the region from
northwest to southeast, and is likely to lift northward toward Lake
MI overnight. Large-scale ascent will remain weak until late in the
period. Nevertheless, strong instability within a very moist and
unstable airmass will support isolated severe wind gusts potential
through peak heating with any storms that develop. Additional storms
may develop overnight from WI into northern IL as the low-level jet
noses into the region resulting in strong warm advection atop the
surface boundary. While this activity may remain elevated above the
nocturnal stable layer, some potential for strong gusts or marginal
hail is possible.
..Leitman.. 06/08/2026
$$
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