Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
438 AM EDT Mon Mar 14 2022

Valid 12Z Mon Mar 14 2022 - 12Z Thu Mar 17 2022

...Upper Great Lakes...
Day 1...

A 110-120kt 250mb jet streak traversing Ontario and Quebec will
provide deep-layer ascent via the right-entrance region in a
narrow ribbon across central MN eastward through portions of
northern WI into the southern U.P. and northern L.P of MI. Hi-res
guidance has come into better agreement with the latest cycle
regarding the latitudinal placement of the most favorable low-mid
level frontogenesis and resulting heavy snow band, but some spread
still exists given the very narrow nature of this feature. With
regard to intensity, there is also better agreement that the best
lift will occur outside (above and below) the DGZ, which has
resulted in a meaningful decrease in WPC probabilities for greater
than 4 inches of snow (down to a peak of 20-40% odds over portions
of NE WI and the far southern U.P of MI). The more bullish hi-res
members include the ARW, ARW2, NAM-nest, and HRRR which depict
localized totals in excess of 6 inches. The latest WPC forecast
calls for an average of 3-5" of snow along this west-east oriented
band, but locally higher amounts are certainly possible where the
more idealized lift within the DGZ is realized.


...Pacific Northwest into the Rockies...
Days 1-3...

Another distinct shortwave trough will move ashore the Pacific
Northwest later tonight, opening up into a large scale trough
while deamplifying/stalling out on D2 as the synoptic pattern
becomes more blocked. WPC probabilities for more than 6 inches are
high in the WA Cascades and moderate in the Olympics on D1/D2,
with moderate probabilities then extending into the OR Cascades,
portions of the northern Rockies, Sawtooths, and Teton Range on
D2. The trough looks to re-amplify as it crawls slowly east on D3,
due to ridging upstream over the Pacific Northwest. This sends
moderate probabilities for more than 6 inches farther south into
the Rockies and Front Range.


Churchill