Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
426 PM EDT Fri Nov 03 2023

Valid 00Z Sat Nov 04 2023 - 00Z Tue Nov 07 2023

...Northwest to Northern Rockies...
Days 1/2...
On the heels of an eastward shifting ridge axis, the next round of
elevation snowfall is expected to arrive overnight across the
Cascades with another atmospheric river. In spite of strong
dynamic forcing and PWATs 1-2 sigma above climatology forecast to
infiltrate the interior Northwest, rising snow levels above 10,000
feet will limit snowfall to the highest peaks of the Cascades. By
Sunday, a progressive shortwave embedded within strong zonal flow
will renew mountain snow chances across the Absaroka and Wind
River Ranges, with 30-50% probabilities of snowfall >4" noted by
Sunday evening which persists into Monday.

As we near Day 3, a series of Eastern Pacific shortwaves embedded
within the flow will support a gradually amplifying mean trough
and height falls across the Pacific Northwest. The resulting
decrease in snow levels, combined with left-exit jet dynamics and
strong onshore flow yield appreciable probabilities (50-70%) of
mountain snowfall >4" in the peaks of the Cascades and Boise
Mountains.


...Northern North Dakota...
Day 2...
Low-level isentropic ascent atop a shallow subfreezing airmass
will usher in some risk of freezing rain along the North
Dakota-Canadian border, as scattered 10-20% probabilities for a
tenth inch remain. 

Asherman