Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Sun Apr 14 2019

Valid 12Z Sun Apr 14 2019 - 12Z Wed Apr 17 2019


...Great Lakes...

Models continue to show rain changing to snow along the northwest
quadrant of a well-defined low lifting northeast from the lower
Ohio valley toward the Great Lakes on Sunday.  Mesoscale banding
supported by low to mid level frontogenesis may produce some
moderate to heavy precipitation rates which may raise the
potential for accumulating snow even during the day across
portions of northern Illinois and southern Wisconsin.  However,
the greater potential for significant accumulations will occur
during the evening into the overnight hours farther to the
northeast across central and northern Lower Michigan where WPC
probabilities show a Moderate to High Risk for accumulations of
4-inches or more during the Day 1 period (ending 12Z Monday).

...Western U.S....

As low pressure moves across central Canada, a trailing frontal
boundary extending back into the western U.S. is expected to
linger across Wyoming.  This boundary, along with low amplitude
mid level energy and favorable upper jet forcing will support
locally heavy mountain snows from the Idaho-Wyoming border into
northwestern Wyoming, where a Moderate Risk for accumulations of
8-inches or more is indicated during the Day 1 period.

Models show a more defined trough moving onshore late Monday,
bringing snows back into the Cascades and Sierra, while continuing
farther east along the previously noted baroclinic band extending
across the Great Basin into the Rockies.

As the upper trough continues to move east, snows will taper off
across the Cascades and Sierra while continuing along the northern
into the central Rockies into early Tuesday.

Pereira