Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
507 PM EDT Mon Mar 23 2020

Valid 00Z Tue Mar 24 2020 - 00Z Fri Mar 27 2020


Days 1-3...

...Northeast...
Snowfall associated with a developing system moving up the coast
is expected to continue into the evening hours, with models
continuing to present a strong signal for impactful amounts across
portions of northern New England.  Latest WPC PWPF shows greater
than 50 percent probabilities for snow accumulations of 6-inches
or more across portions of central and southern New Hampshire and
western Maine during the Monday evening to the overnight hours. 
This system is forecast to move into the Canadian Maritimes, with
snow diminishing Tuesday morning.  Models show a second system
moving through the Ohio valley Tuesday night, with a coastal low
developing Wednesday morning.  Apart from the colder NAM, most of
the 12Z guidance showed limited potential for significant snow
accumulations - with the general consensus showing light
accumulations across the higher elevations of northern
Pennsylvania to Upstate New York and New England.

...Northern Plains to the Northern Great Lakes...
A mid level shortwave and associated surface low are forecast to
move across central Canada on Tuesday with a trailing cold front
dropping southeast across the north-central U.S.  Upstream
energy/favorable upper jet forcing are expected to support a
stripe of generally light amounts north of the front across South
Dakota Wednesday morning and then across northern Wisconsin and
the U.P. of Michigan late Wednesday into early Thursday.

...Western U.S....
Models a broad positively-tilted upper trough settling southeast
across the western U.S. this period.  This is expected to produce
some high elevation, locally heavy amounts across portions of the
Pacific Northwest, northern California and the northern Rockies
Monday night and Tuesday.  Expect at least light amounts to
continue into Tuesday night across this region, with models
offering some indication of locally heavy amounts supported by a
low-to-mid level frontal zone settling south across the Rockies
and Sierra.  Areas impacted are expected to include the Sierra and
the northern Utah ranges - where WPC PWPF is indicating higher
probabilities for accumulations of 8-inches or more late Tuesday
into Wednesday.  As the front lingers across the region, some
areas from the Sierra through the Great Basin into the Rockies may
see additional significant amounts Wednesday night into Thursday.

For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Pereira