spc ac 291900
day 3 convective outlook
nws storm prediction center norman ok
0200 pm cdt mon jun 29 2026
valid 011200z - 021200z
...there is a marginal risk of severe thunderstorms from the central
plains to the upper midwest/great lakes...and across the
northeast...
...summary...
isolated strong to severe storms will again be possible from the
central plains into the upper midwest as well the northeast on
wednesday. severe wind gusts and large hail are the main concerns.
...synopsis...
the overall synoptic pattern will not changes much from day
2/tuesday into day 3/wednesday. the upper ridge over the eastern
u.s. may shift slightly east while an upper trough persists over the
west. a series of midlevel shortwave impulses will migrate across
the northern plains and upper midwest/great lakes vicinity. enhanced
mid/upper flow will persist from the dakotas into the great lakes
and over the northeast.
...upper midwest/great lakes...
a quasi-stationary boundary is forecast to extend from northern wi
toward southeast sd wednesday morning. this boundary may slowly lift
northward during the afternoon. the evolution of this boundary will
largely be influenced by morning convection that may be ongoing
near/north of the boundary across parts of mn/wi at the beginning of
the period. given a very moist airmass, strong to extreme
instability is forecast near and south of the boundary. morning
convection could weaken as it lifts north of the boundary, or it
could intensify through the day as destabilization occurs, spreading
east across the upper great lakes. another round of convection may
develop during the late afternoon into the nighttime hours along the
boundary as well. while convective evolution is uncertain, the
thermodynamic and kinematic parameter space will support a risk for
severe wind gusts and large hail. enhanced low-level shear near the
surface boundary could also result in a corridor of tornado
potential. higher severe probabilities will likely be needed in
subsequent outlooks as mesoscale details and convective evolution
become more clear and forecast confidence increases.
...northeast...
large-scale ascent will not be as strong across the region on
wednesday, though forecast guidance does show a shortwave impulse or
mcv moving across the area as it crosses the international border
from canada. a very moist and strongly unstable airmass will be in
place and strengthening mid/upper northwesterly flow will support
some organized severe risk. however, storm coverage remains
uncertain. strong downburst winds and isolated large hail will be
possible. the wind risk could increase if sufficient storm
coverage/interaction results in clustering/bowing segments, but this
scenario is uncertain given a lack of stronger low-level jet. trends
will be monitored and higher severe probabilities may be needed in
subsequent outlooks.
...central high plains...
a surface trough will extend southward from western sd/ne into
eastern co/nm on wednesday. southerly low-level flow will maintain
modest boundary layer moisture beneath steep midlevel lapse rates.
southerly flow through around 500 mb will be somewhat weak, though
southwesterly flow increases substantially above that. this could be
sufficient for weakly organized convection developing within upslope
flow along the surface trough wednesday afternoon/evening. given
weaker instability and more modest vertical shear compared to
previous days, severe potential is more uncertain. however, strong
outflow gusts still appear possible given a deeply mixed boundary
layer and inverted-v sub-cloud thermodynamic profiles.
...southeast...
isolated to scattered thunderstorms are likely to develop on the
southern periphery of the upper anticyclone wednesday afternoon. a
very moist and strongly unstable airmass will be in place, but
vertical shear appears a bit weaker compared to day 2/tuesday. storm
coverage is uncertain, but some risk for locally strong gusts may
develop, especially if sufficient clustering can occur to promote
forward propagation.
..leitman.. 06/29/2026
click to get wuus03 ptsdy3 product
note: the next day 3 outlook is scheduled by 0730z