SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 AM CDT Mon Jun 27 2022
Valid 291200Z - 301200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY
AFTERNOON INTO WEDNESDAY NIGHT ACROSS MUCH OF SOUTH DAKOTA AND
SOUTHERN/EASTERN NORTH DAKOTA INTO MUCH OF CENTRAL/NORTHERN
MINNESOTA AND THE ADJACENT WESTERN LAKE SUPERIOR AREA...
...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...
Models suggest that blocking may begin to become more prominent once
again during this period across the northeastern Pacific and
adjacent northwestern North America vicinity, with a mid/upper high
slowly beginning to form across Alaska/Yukon. Downstream of this
regime, a deep mid-level low emerging from the Canadian Arctic
latitudes is forecast to continue to slowly dig to the west of
Hudson Bay. The increasingly deformed remnants of another low,
emerging from persistent mid-level troughing offshore of the Pacific
coast, appear likely to merge into the broader-scale cyclonic flow
to the south of the more prominent digging low. Models indicate
that this will be accompanied by 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 central 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.
Meanwhile, in lower latitudes, lower/mid-tropospheric ridging will
prevail across much of the central and southern tier of the U.S.
While a return flow of monsoonal moisture will continue around the
western through northern periphery of the ridging, across and
north-northeast of the Southwest and southern Rockies vicinity,
seasonably high boundary-layer moisture content will remain largely
confined to the Southeast and northwest Gulf Coast states.
...Northern Great Plains into Upper Great Lakes region...
Within the deepening surface troughing, boundary-layer moistening
may largely be confined to that associated with gradual continued
evapotranspiration/return of evapotranspiration driven moistening
from the Corn Belt. Models do suggest that surface dew points could
increase above 60F, with perhaps localized pockets of mid 60s F.
However, beneath the plume of warm elevated mixed-layer air, this
may only yield generally modest mixed-layer CAPE on the order of
1000-1500+ J/kg across most areas.
The lack of more substantive low-level moistening, coupled with the
strong inhibition, continues to contribute to uncertain severe
weather potential for this period. However, models suggest that at
least widely scattered thunderstorm development is possible during
the late afternoon and evening, which could include isolated
supercells capable of producing severe hail and locally strong
surface gusts. And, though there is sizable spread, there is at
least some signal within the various model output that large-scale
forcing for ascent could become supportive of an upscale growing
cluster of thunderstorms Wednesday night. It appears that this
could occur anywhere from entirely north of the Minnesota
international border to south of the international border. However,
if this occurs, the strong wind fields, coupled with the dry
well-mixed sub-cloud air, could contribute to strong outflow capable
of producing severe wind gusts.
..Kerr.. 06/27/2022
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