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Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1150 PM CDT Mon Jun 27 2022

Valid 291200Z - 301200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY
AFTERNOON INTO WEDNESDAY NIGHT ACROSS PARTS OF NORTHWESTERN
NEBRASKA...MUCH OF SOUTH DAKOTA...SOUTHERN AND EASTERN NORTH
DAKOTA...CENTRAL AND NORTHERN MINNESOTA AND THE WESTERN LAKE
SUPERIOR VICINITY...

...SUMMARY...
Strong thunderstorms may impact a corridor across the northern Great
Plains into portions of the Upper Midwest late Wednesday afternoon
into Wednesday night, posing at least some risk for severe wind and
hail.

...Synopsis...
It appears that blocking may begin to beco*e more prominent once
again within the large-scale flow across the northeastern Pacific
and adjacent northwestern North America, with a mid-level high
slowly beginning to form and strengthen over the Alaska/Yukon
vicinity during this period.  Downstream of this regime, a deep
mid-level low emerging from the Canadian Arctic latitudes is
forecast to continue slowly digging to the west of Hudson Bay.  As
this occurs, the increasingly deformed remnants of another low,
emerging from persistent mid-level troughing offshore of the U.S.
Pacific coast, appear likely to accelerate inland within a confluent
regime along the Canadian/U.S. border, between the more prominent
digging low and flattening mid-level ridging across the northern
U.S. Great Plains.

Within deepening surface troughing to the lee of the Canadian and
northern U.S. Rockies, models indicate that this will be acco*panied
by at least weak cyclogenesis across the southern Canadian Prairies
into northwestern Ontario Wednesday through Wednesday night, along
with strengthening southwesterly to westerly lower/mid tropospheric
wind fields across the northern Great Plains into Upper Midwest and
Canadian/U.S. border vicinity.  Coincidentally, a plume of very warm
and capping elevated mixed-layer air is forecast to nose northeast
of the Rockies, toward the Upper Midwest/Great Lakes region.

In lower latitudes, lower/mid tropospheric ridging likely will
prevail across much of the central and southern tier of the U.S. 
While a return flow of monsoonal moisture across and north-northeast
of the Four Corners region into the northern Great Plains may
develop, seasonably high boundary-layer moisture content still
appears likely to remain mostly confined to the Southeast and
western Gulf Coast states.

...Northern Great Plains into upper Great Lakes vicinity...
Within the deepening surface troughing, boundary-layer moistening is
still expected to be largely confined to that associated with
gradual continued evapotranspiration and northward return of
evapotranspiration driven moistening from the Corn Belt.  Despite
steepening lower/mid tropospheric lapse rates, this may only
beco*ing supportive of weak to modest mixed-layer CAPE in most
areas.  However, guidance has been indicating that at least somewhat
higher dew points will develop and be maintained beneath the
strengthening mid-level inhibition, along a developing surface warm
front shifting northeast of the middle Missouri Valley by early
Wednesday.  This will probably contribute to at least a narrow
corridor of more substantive potential instability, with largest
CAPE probably beco*e focused near the intersection of the warm front
and the lee surface trough. By late afternoon, it appears that this
may be roughly located near or north of the eastern North and South
Dakota state border.  The possible magnitude of the CAPE is more
uncertain, but at least a localized area of 2000+ J/kg seems
increasingly probable.

Mid/upper forcing to support thunderstorm initiation is also
unclear.  At some point during the late afternoon or early evening,
it is possible that weakening inhibition due to daytime heating or
lift aided by low-level warm advection could support isolated
thunderstorm development.  If this occurs, the environment will be
conducive to supercells capable of producing large hail, locally
strong wind gusts and perhaps a tornado or two, and a strengthening
low-level jet (up to 50+ kt around 850 mb) could support the
evolution of a small northeastward propagating organized convective
system Wednesday evening.  Due to the large continuing spread in the
model output, severe probabilities are being maintained at
"Marginal" risk levels.  However, it is possible this could be
increased in later outlooks, if/when guidance co*es into better
agreement on sub-synoptic developments.

Otherwise, there has been a signal that a cluster of thunderstorms
may spread east of the higher terrain of Wyoming (perhaps in
association with the monsoonal regime) by late afternoon.  As this
activity progresses into/across the strongly heated and deeply mixed
boundary-layer over parts of western Nebraska into western South
Dakota, it may pose a risk to produce a few strong wind gusts into
Wednesday evening.

..Kerr.. 06/28/2022