ACUS01 KWNS 050600
SWODY1
SPC AC 050559

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Sat Oct 05 2024

Valid 051200Z - 061200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
NORTHERN WISCONSIN AND ADJACENT PORTIONS OF SOUTHERN UPPER MICHIGAN...

...SUMMARY...
Isolated strong to severe thunderstorms may produce hail and gusty
winds across parts of northern Wisconsin into the Upper Peninsula of
Michigan this evening.

...Synopsis...
Flow aloft will remain generally weak over the southern half of the
U.S. today, where upper ridging will prevail.  This ridging will --
however -- be interrupted by an elongated/weak trough comprised of
several smaller-scale vorticity maxima, extending from the
southeastern states west-southwestward across the Gulf of Mexico to
northern Mexico.

Farther north, a faster belt of westerly flow will prevail, with an
embedded/potent short-wave trough forecast to move across the
northern Plains through the day, and then the Upper Mississippi
Valley/Upper Great Lakes region overnight.

Accompanying the upper trough, a surface low is forecast to advance
east-northeastward across the Canadian Prairie, and into
northwestern Ontario through latter stages of the period.  A
trailing cold front will shift eastward across the north-central
U.S. and southward across the Plains -- reaching a position from
Lower Michigan southwestward to the Ozarks, and then
west-southwestward across Oklahoma to Far West Texas by Sunday
morning.

...Central and northern Wisconsin north to Lake Michigan...
As a cold front advances across the Upper Midwest area through the
afternoon, a capped boundary layer should hinder convective
development.  As the boundary crosses the Upper Mississippi Valley
around sunset, and the upper system advances, the combination of
strong ascent and steepening lapse rates aloft should permit
eventual development of showers and scattered thunderstorms.

With a rather dry -- and nocturnally stabilizing -- boundary layer
expected ahead of the front, convection should evolve within a
slightly elevated but amply unstable layer.  Strong southwesterly
flow aloft will provide sufficient shear for organized/rotating
storms -- and thus risk for hail is evident.  Additionally, the
strongly dynamic upper system/strong mass response suggests
potential for downward transport of strong flow aloft -- potentially
manifesting as severe-caliber wind gusts at the surface.  Given the
overall severe risk, will introduce a small SLGT/level 2 risk across
this area, with the primary risk expected to be hail.  However,
potential for strong/gusty surface winds may  also -- depending upon
boundary-layer evolution -- warrant upgrade to 15% probability in
later outlooks.

..Goss/Squitieri.. 10/05/2024

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