ACUS02 KWNS 250608
SWODY2
SPC AC 250607

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0107 AM CDT Sun Aug 25 2024

Valid 261200Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS
OF EASTERN SOUTH DAKOTA INTO SOUTHERN WISCONSIN...AND SMALL PORTIONS
OF SURROUNDING STATES...

...SUMMARY...
Severe storms are expected to evolve within a zone extending from
the northern High Plains eastward to the Wisconsin vicinity during
the afternoon and evening Monday. A few severe storms are also
expected across the Northeast and Mid-Atlantic region.

...Synopsis...
A weakening upper trough is forecast to remain across the central
U.S. Monday. On the northwestern periphery of this ridge, and
short-wave trough initially over the Intermountain West is forecast
to advance northeastward across the northern High Plains into the
Northern Plains through the period. Meanwhile, an upper low is
forecast to shift southward out of the St. Lawrence Valley area
across western/southern New England, before shifting offshore
overnight. Finally, a Gulf of Alaska upper trough is forecast to
advance into western Canada and the Pacific Northwest through
Tuesday morning.

At the surface, a northwest-to-southeast cold front is forecast to
extend from the northeastern Minnesota vicinity southwestward across
Nebraska early in the period. The front should move little through
the day, as a frontal low lingers in the vicinity of the
Mid-Missouri Valley area. Overnight, the low is forecast to shift northeastward, allowing the trailing portion of the cold front to
progress southward across the central Plains through latter stages
of the period.

...Northern High Plains east to parts of Wisconsin...
Thunderstorms may be ongoing across portions of northern Minnesota
early Monday morning, with limited severe risk potentially lingering
through roughly midday. Meanwhile, as the moist low-level airmass
heats near and south of the convectively reinforced front,
mixed-layer CAPE in the 3000 to 5000 J/kg range is forecast to
develop through the afternoon. This, combined with ascent near the front/convective outflows, should allow isolated storms to develop
across the eastern South Dakota vicinity. The storms should rapidly
become supercells, given the kinematic environment characterized by
low-level flow veering/increasing with height to 40 to 50 kt
southwesterlies at mid levels. Very large hail is expected, along
with damaging wind gusts. Storms will continue into the evening,
possibly growing upscale into an MCS overnight -- shifting
northeastward into/across southern Minnesota. Along with continued
risk for large hail, damaging winds would likely accompany this
convection. In addition, a couple of tornadoes may also occur --
particularly just to the northeast of the anticipated position of
the surface low where low-level flow will remain
backed/southeasterly.

Meanwhile farther west, into the High Plains, isolated afternoon
convective development is expected, in closer proximity to the
advancing upper system. A drier boundary layer and thus weaker CAPE
across this region suggests less substantial severe risk. Still,
hail and damaging gusts should accompany a few of the stronger
storms, given the belt of 50 kt mid-level southwesterly flow
accompanying the advancing short-wave trough.

...Portions of the Northeast/New England...
As the upper low shifts southward across western New England through
the day Monday, heating/destabilization is expected to support
development of isolated to scattered thunderstorms. Enhanced
northwesterly flow near and west of the low should support
southeastward-moving bands/clusters of storms, which should prove
locally capable of producing strong -- potentially damaging -- gusts
from mid afternoon into the evening hours.

..Goss.. 08/25/2024

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