spc ac 281909
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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note: the next day 3 outlook is scheduled by 0730z