885
ACUS48 KWNS 080847
SWOD48
SPC AC 080845

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0345 AM CDT Mon Jun 08 2026

Valid 111200Z - 161200Z

...DISCUSSION...
...Day 4/Thursday...

An active period of severe weather is expected from the upper Great
Lakes into Ozark Plateau, with the most concentrated and potentially
most significant severe storms affecting parts of the Midwest.

Within the base of an upper low centered over Manitoba and northwest
Ontario, the models are in good agreement in depicting the
progression of a potent short-wave trough and attending
mid/upper-level jet streaks through the upper Midwest and upper
Great Lakes. There is some model signal that a trailing perturbation
on the immediate cyclonic side of the mid-level jet will overspread
the mid MS Valley Thursday night.

At the surface, a deepening surface low/frontal wave is expected to
develop from central IA into the southern UP of MI during the day,
along a cold front advancing through the upper Midwest and into the
upper Great Lakes. The southwest extension of that boundary will
progress southeast through the lower MO and Mid MS Valleys, while
becoming quasi-stationary across the southern Plains. The specific
boundary location across the Midwest may be modified to some extent
from a thunderstorm complex moving through the area Wednesday
night/early Thursday.

A very moist air mass is expected to reside to the south of the
surface front, which coupled with modestly steep mid-level lapse
rates is expected to yield moderate to strong instability. The
presence of a 50-70 kt mid-level jet streak attending the short-wave
trough will result in relatively strong deep-layer shear along the
frontal zone, with vector orientation becoming increasingly parallel
to the boundary with southward extent. The overall pattern appears
supportive of an organized severe-weather episode from the upper
Great Lakes into mid MS Valley. There is some model signal that a
corridor of enhanced tornado potential could develop along and south
of the surface low track from eastern IA and northern IL into
central and southern WI. That potential scenario will be dictated by
the location of the effective surface boundary.

Additional, more isolated severe storms appear possible across parts
of the Northeast.


...Day 5/Friday...

A number of the 00z models progress a lower-latitude short-wave
trough through the upper OH Valley and lower Great Lakes, which is a
departure from previous model runs. That scenario would increase
severe-weather potential across those areas into New England, and
perhaps the Mid-Atlantic, given the potential for a moderately
unstable air mass across the pre-frontal warm sector. Should
subsequent model runs remain consistent with this recent trend, an
unconditional 15% probability contour may be needed in the next
forecast update.

Elsewhere, Isolated severe storms appear possible across portions of
the southern High Plains.


...Day 6/Saturday...

The ensemble mean solutions are in good agreement in depicting a
mid/upper-level low over Hudson Bay with a belt of strong mid-level
flow extending from slight troughing over the northern High Plains
into the Great Lakes and Northeast. There is more spread across the
deterministic models with respect to the longitudinal position of
that trough, and the position of the associated frontal system. In
general, it appears some severe weather threat could materialize
across the central Plains. However, confidence in that scenario is
low.


...Days 7 and 8/Sunday and Monday...

The ensembles indicate a gradual amplification of the large-scale
pattern, featuring troughing from Hudson Bay into the MS Valley, and
upstream ridging across western Canada and the Pacific Northwest.
The location of any relevant surface frontal systems remains highly
uncertain, as does the location(s) of any severe-weather threat.

..Mead.. 06/08/2026