Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
450 AM EDT Fri Apr 05 2019

Valid 12Z Fri Apr 05 2019 - 12Z Mon Apr 08 2019


...Mountainous Western U.S....
Days 1-3...

Low pressure well off Washington drifts east through Friday night
before shifting north across the Gulf of Alaska through Sunday. A
series of shortwaves spin off this low and into the Pacific
Northwest through Saturday before an Atmospheric River pushes
inland as the low retreats north through Sunday night. Snow levels
decrease through tonight as the low approaches (3000ft over WA is
the lowest level) with a notable baroclinic zone in the warm
atmospheric river Sunday into Monday with very high snow
elevations on the south end of the river. Locally heavy snow is
expected in the mountains ahead of these shortwaves and their
associated frontal bands, including the Olympics, Cascades and
Sierra Nevada to the central Rockies. Heavy snow is limited to the
highest northern CA, Oregon, Idaho, Wyoming, Utah, and Colorado
peaks from Day 1 into Day 2 with moderate probabilities for six
inches for these peaks. Washington state will have nearly
continuous precipitation Days 1-3 with one to two feet likely for
the highest Olympics and northern Cascades across the three days.


...Northeast...
Day 1...

Low level theta-e advection into the Northeast CONUS which is
currently occupied with a 1034mb surface high will support a
period of mixed precipitation for higher elevation areas northeast
from northeastern PA and much of Maine today through tonight.
Mountain snows in the Adirondacks and Green/White mountains have a
moderate probability of two or more inches today with the more
notable threat being late season freezing rain. Pockets of
freezing rain, mainly tonight warrant moderate risks for a tenth
inch of ice for the Catskills, southern Adirondacks and
Berkshires.


...Minnesota Arrowhead...
Days 2-3...

Strong warm advection ahead of a shortwave trough emanating from
the West is expected to support increasing precipitation across
the Upper Midwest Sunday morning. Confluent downstream flow will
support high pressure and a chance for mixed precipitation across
northern Minnesota, with WPC probabilities indicating a Slight
Risk for ice accumulations of 0.25 inch or more over the Arrowhead
from Day 2 into Day 3.

Jackson