Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
156 PM EST Fri Feb 04 2022

Valid 00Z Sat Feb 05 2022 - 00Z Tue Feb 08 2022

...Pacific Northwest and Northern Rockies...
Day 1...

A shortwave trough moving across the Pacific Northwest tonight
will shift quickly eastward as a pronounced mid-level ridge builds
across the Pacific. This shortwave will be accompanied by modest
upper diffluence and PWs reaching above 0.5" to produce moderate
to heavy snow from the WA Cascades into the Northern Rockies. The
transient nature of this feature will limit total snowfall, but
WPC probabilities continue to be above 50% for more than 6 inches
across the Northern Rockies, and 30-40% in the WA Cascades. With
snow levels around 3000 ft, accumulating snow is likely at
Snoqualmie, Stevens, and Marias passe as well.


...Northern Minnesota and Northern Great Lakes...
Days 1/2...

A fast moving low pressure dropping out of Alberta, Canada will
move across the Northern Plains and northern MN Saturday before
lifting northeast into Ontario on Sunday. Although this feature is
quick to exit, it will be accompanied by WAA to produce enhanced
moisture noted by PWs of +1 standard deviation above the climo
mean and modest RRQ diffluence behind a departing jet streak.
Together these will create a swath of snowfall, which could be
moderate to heavy at times as modest fgen leads to potential
banded structures within the WAA and snowfall rates of more than
0.5"/hr. With the temporal duration of snowfall lengthening due to
system-parallel bands, moderate to heavy accumulation is likely
across northern MN where WPC probabilities for 4+ inches are
10-30%.

Further to the east, some enhancement due to southerly flow off
Lake Superior ahead of the low will upslope into the Iron Ranges
of the Arrowhead, and WPC probabilities are high for 4+ inches
D1.5, with locally more than 6 inches possible. Additionally, long
duration fetch of southerly flow across Lake Michigan could
produce some enhanced LES on the northern side of the lake across
the eastern U.P. between Manistique and Mackinaw City. WPC
probabilities for 4+ inches are high, and with snow fall rates
likely exceeding 1"/hr at times, could reach 8" in some areas.

Weiss