Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
232 AM EST Fri Dec 15 2023

Valid 12Z Fri Dec 15 2023 - 12Z Mon Dec 18 2023

...Northern Plains and Upper Midwest...
Models continue to depict a complex scenario, with at least light
snow accumulations expected to develop Friday into the overnight
across portions of the region.  A northern stream wave centered
over the northern Plains this morning is forecast to drift east
ahead of a more-defined and amplifying wave digging southeast from
Canada into the Dakotas this evening.  There this energy will
begin to phase with a southern stream low lifting out of the
central Plains.  Precipitation is expected to develop initially
along a frontal band extending from northern Minnesota through the
upper Great Lakes.  Although some mixing is expected, thermal
profiles suggest mostly rain and limited snowfall accumulations
during the day.  However, the threat for accumulating snow is
expected to increase by the evening and continue into the
overnight hours as the waves begin to phase and a new upper low
develops.  The increase in upper forcing along with lingering
low-to-mid level frontogenesis will help support a period of
increasing precipitation rates and a changeover to snow along the
northwest side of the precipitation shield.  While not expected to
be a widespread heavy snow event, the models have trended wetter
and the signal for at least a few inches of wet snow has increased
across portions of the area.  WPC guidance now shows a stripe of
moderate probabilities (40-70 percent) for snow accumulations of 2
inches or more centered over central Minnesota into far northwest
Wisconsin. 

Some light snow is forecast to continue into early Saturday,
followed by drier conditions that are expected to continue through
Sunday.  Then an amplified shortwave sharpening over Upper
Midwest/Great Lakes will support lake enhanced snowfall beginning
Sunday night with at least a few inches likely over the western
U.P. by Monday morning.

Pereira