Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
415 PM EST Tue Feb 05 2019

Valid 00Z Wed Feb 06 2019 - 00Z Sat Feb 09 2019


...Western U.S....

There remains a good signal for heavy snows across portions of the
southwestern U.S., particularly along the Mogollon Rim through
central Arizona, as well as across parts of the central Rockies,
including the Wasatch, San Juan and Elk mountains.  Models show a
deep upper trough and associated baroclinic zone bringing the
strong potential for heavy snow accumulations as they move across
the region Tuesday night into Wednesday.

...Midwest and Great Lakes...

Models continue to show two systems bringing widespread snow and
significant icing to portions of the region beginning later today.
 The initial system - a low amplitude shortwave embedded within
deep southwesterly flow - is forecast to lift across the upper
Mississippi valley and Great Lakes Tuesday evening into the
overnight hours.  Overall, models have remained consistent in
showing warm air advection eroding the low level cold air while
subfreezing surface temperatures remain locked in place. 
Meanwhile, a developing upper jet couplet may support an area of
enhanced lift - further setting the stage for a significant a
freezing rain event across portions of northern Illinois, southern
Wisconsin and southern Lower Michigan Tuesday evening into early
Wednesday.  This area includes portions of the Chicago, Milwaukee
and Detroit metropolitan regions.  With deeper cold air remaining
in place, there is greater potential for significant snows across
parts of northern Wisconsin into the Upper Peninsula.

This initial system is expected to move completely east of the
region by late Wednesday.  However, as the upper trough in the
west continues to move east, precipitation is expected begin
spreading east across the region again by Wednesday evening. 
Overall, models have remained fairly consistent with this system
as well, showing widespread snows, with locally heavy snows
developing northwest of the associated surface low as it tracks
northwest from the mid Mississippi valley through the upper Great
Lakes on Thursday.  Strong upper forcing along with low to mid
level frontogenesis is expected to enhance the potential for
locally heavy accumulations from eastern Minnesota into northern
Wisconsin and the Upper Peninsula Thursday afternoon and evening. 
While the models are less bullish with amounts, another icy
transition zone is expected farther to the south, with significant
ice accumulations possible from parts of southern Wisconsin to
northern Lower Michigan.

...Northeast...

The initial system impacting the Midwest on Day 1 will bring
freezing rain to portions of the interior Northeast Wednesday into
early Thursday.  A cold air wedge extending southeast from eastern
Canada will support some significant ice accumulations across
portions of Upstate New York and interior central New England. 

A wintry mix ahead of the next system may result in some lighter
ice amounts across parts of northern New England before
precipitation changes to rain on Friday.

Pereira