Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Thu Apr 28 2022

Valid 12Z Thu Apr 28 2022 - 12Z Sun May 01 2022

...Northern Rockies to Northern Great Plains...
Days 1-2...
An amplifying and negatively-tilted upper trough will push through
Oregon this evening on the nose of a 110kt jet. Snow over eastern
Oregon this morning will stream eastward across central central
Idaho and into western Wyoming as a 700mb low redevelops over the
Bitterroots. Heavy snow will develop on its northwest side across
western Montana early Friday and spreading eastward through the
day, including through the Bighorns in Wyoming. The system will
continue to deepen as it moves into the western Plains, closing
off at 500mb as well with a surface low pressure deepening well
south of the region. With marginally cold air in place east of the
Rockies, some light snow is possible over the Dakotas with
exception being over the Black Hills where temperatures should
support more accumulation. Several inches are possible there with
windy conditions as well. Farther south, a few inches of snow are
possible over the northern CO ranges as well. WPC probabilities
for at least 4 inches of snow are high (>70%) over western Montana
where more than 8 inches is possible.

...Maine...
Days 1-2...
Slow-moving cutoff low over Nova Scotia will loop back through the
Gulf of Maine on Friday as its surface low slowly wobbles
eastward. Colder air funneled in from the north/northeast will
favor rain changing to snow, especially overnight, as
precipitation wraps around the stacked circulation. Two-day totals
in excess of a couple inches will be confined to interior
locations and especially from the Central Highlands northeastward
to Caribou. Some upslope enhancement will yield spotty areas of 6
inches or more. WPC probabilities for at least 4 inches are
moderate (>40%) over northeastern areas of the Pine Tree State.


For day 3, the probability of at least 4 inches of snow is less
than 10 percent.

For days 1-3, the probability of significant icing greater than
0.25 inches is less than 10 percent.

Fracasso