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Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0211 AM CDT Sun Jun 26 2022

Valid 281200Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
AFTERNOON AND EVENING ACROSS PARTS OF NORTHERN AND CENTRAL
MONTANA...AS WELL AS CENTRAL AND SOUTHERN WISCONSIN AND ADJACENT
PORTIONS OF SOUTHEASTERN MINNESOTA AND NORTHEASTERN IOWA...

...SUMMARY...
Strong thunderstorms may impact parts of the northern Rockies
vicinity, as well as parts of the Upper Midwest, Tuesday afternoon
and evening, acco*panied by at least some risk for severe weather.

...Synopsis...
Models indicate little change to the large-scale flow across the
northeastern Pacific and adjacent portions of northwestern North
America, but a lingering co*pact low emerging from persistent
mid-level troughing offshore of the U.S. Pacific coast is forecast
to migrate inland of the Pacific Northwest coast during this period.
It appears that short wave ridging downstream of this perturbation
may lose some amplitude while shifting across and east of the
northern U.S. Rockies.  However, this may mostly occur due to a
subtle impulse progressing through the crest of the ridging, in
advance of the low, rather than the influence of a much more
prominent mid-level low beginning to dig southeast of the central
Canadian Arctic latitudes.

Downstream of the ridging, mid-level troughing is forecast to
generally turn eastward to the south of Hudson Bay.  It appears that
the most prominent perturbation embedded within this feature will
migrate across northern Ontario through the southern Hudson/James
Bay vicinity by late Tuesday night, but another fairly vigorous but
more co*pact impulse probably will dig across the U.S. Upper Midwest
into upper Great Lakes region.

The lead troughing will by acco*panied by another reinforcing cold
front, in the wake of a more prominent preceding front which will
continue to weaken across the Gulf Coast vicinity.  While seasonably
high boundary-layer moisture content will likely remain confined to
the Gulf Coast, some gradual boundary-layer moistening may continue
ahead of the next front, across parts of the Upper Midwest, and into
deepening surface troughing to the lee of the Canadian/Montana
Rockies.

...Upper Midwest...
In advance of the digging short wave impulse, and an associated
northwesterly mid-level jet streak (50+ kt around 500 mb), models
suggest that a pre-frontal corridor of boundary-layer warming and
modest moistening may contribute to CAPE in excess of 1000 J/kg,
beneath relatively cool mid-level air.  Aided by steep low-level
lapse rates, and wind fields characterized by modest clockwise
curved low-level hodographs and strengthening deep-layer shear, it
is possible that the environment could beco*e conducive to
supercells capable of producing severe hail and strong surface
gusts.  This seems most likely to beco*e focused across parts of
southeastern Minnesota/northeastern Iowa into central and southern
Wisconsin late Tuesday afternoon and evening.

...Montana...
Within the deepening surface troughing, modest indicate that the
environment will beco*e deeply mixed with strong heating, with
sufficient boundary-layer moisture to support at least weak CAPE on
the order of 500 J/kg.  Aided by forcing for ascent associated with
low-level warm advection, and the weak  mid-level impulse, models
suggest that thunderstorms developing across the mountains during
the afternoon may grow upscale as they propagate eastward off the
higher terrain.  As convection consolidates, downward mixing of
30-40 kt mid-level flow, coupled with melting/evaporation of
precipitation in the very warm, deep and well-mixed sub-cloud
boundary layer, may allow for strong outflow with at least
occasional severe surface gusts as activity spreads eastward across
much of central and northern Montana through Tuesday evening.

..Kerr.. 06/26/2022