spc ac 090540
day 2 convective outlook
nws storm prediction center norman ok
1240 am cdt tue jun 09 2026
valid 101200z - 111200z
...there is an enhanced risk of severe thunderstorms over eastern
minnesota...much of wisconsin...central and eastern iowa...and
northwest illinois...
...summary...
scattered to numerous severe thunderstorms capable of large hail in
excess of two inches in diameter, a few strong tornadoes, and
damaging winds with gusts in excess of 75 mph appear likely across
portions of the upper mississippi valley and midwest wednesday
afternoon into night. more sporadic occurrences of large hail and
damaging winds are possible into the central and southern plains,
and from the lower great lakes toward the mid-atlantic coast.
...synopsis...
an upper low along the mt-sk border wednesday morning is forecast to
deepen while redeveloping to along the nd-mb border wednesday night.
that intensification process will be driven by mid/upper-level jet
streaks moving through the base of broader-scale trough, in tandem
with an amplifying short-wave trough. a lead disturbance initially
over the northern high plains wednesday morning will accelerate
northeast into the upper ms valley by evening, along with the
leading edge of stronger mid/upper-level jet streak winds.
at the surface, an area of low pressure over eastern sd wednesday
morning will develop north-northeast into southeast mb by evening,
while a trailing cold front advances through the upper ms valley
into the upper great lakes. the trailing extension of the boundary
from the mid mo valley into ks will move more slowly through the day
before stalling and then lifting north wednesday night in response
to cyclogenesis over the central plains. a dryline will intersect
the front over southwest ks wednesday afternoon, with that feature
extending southwest into western tx.
...upper mississippi valley/upper great lakes into the central and
southern plains...
areas of thunderstorms may be ongoing wednesday morning across
portions of mn and wi, aided by warm advection along a nocturnal
low-level jet. residual convective outflow boundaries from the
early-day storms and the approaching cold front are expected to
focus the most intense thunderstorm development, which may occur by
early afternoon across northern and central parts of mn. subsequent
south/southwestward storm development is expected by mid/late
afternoon along and ahead of the front from southern mn and western
wi through central/eastern ia, northern mo, into eastern/southern
ks, and perhaps into western ok and northwest tx.
rich boundary-layer moisture, characterized by dewpoints in the
upper 60s to low/mid 70s will coincide with a plume of steep
mid-level lapse rates to yield moderate to strong afternoon
instability with mlcape increasing to 2000-4000+ j/kg across the
warm sector. deep-layer shear will strengthen through the afternoon
into evening with the arrival of the jet streaks, especially across
the upper ms valley into upper great lakes where effective bulk
shear magnitudes of 50-60 kt are forecast.
the expected cape-shear combination will support numerous severe
storms that begin as supercells capable of large to very large hail
and some tornado threat, with an eventual transition to a more of a
cold-pool-driven convective system with embedded bowing structures
by evening across portions of the upper midwest, potentially into
great lakes. damaging wind potential, including the possibility for
75+ mph wind gusts would likewise increase with that mode
transition, as would a continued tornado threat with line-embedded
meso-vortices. the greatest potential for a few strong tornadoes is
expected to develop with any sustained supercells across portions of
eastern mn, wi, eastern ia, and northwest il in the proximity of a
strengthening low-level jet, which will enhance near-ground shear.
storms are expected to be increasingly more isolated in nature with
southwestward extent along the front and dryline from eastern ks
into western ok and northwest tx. nonetheless, the degree of
instability coupled with around 30 kt of deep-layer shear will favor
organized multicell and/or supercell structures capable of large
hail during the afternoon and evening hours.
a separate large-hail threat is expected to develop wednesday night
into thursday morning over the mid mo valley within a zone of strong
warm advection and moisture flux occurring within the terminus of a
50+ kt low-level jet.
...lower great lakes to mid-atlantic coast...
forcing for ascent associated with a weak mid-level disturbance
moving through the region is expected to foster widely scattered
thunderstorm development during the afternoon amidst a moist and
moderately unstable air mass. model soundings indicate some
enhancement of the mid-level wind field, with deep-layer shear
increasing to around 30 kt in some areas. as such, a few severe
storms appear possible with an associated risk for damaging wind
gusts and large hail.
..mead.. 06/09/2026
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note: the next day 2 outlook is scheduled by 1730z