Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
357 PM EDT Tue Mar 15 2022

Valid 00Z Wed Mar 16 2022 - 00Z Sat Mar 19 2022


...Pacific Northwest through the Rockies...
Days 1-3...
A frontal band associated with a broad upper trough will continue
to move through the northern Rockies, producing mostly light to
moderate accumulations across the region this evening and
overnight. Widespread heavy amounts are not expected, however
there is the potential for locally amounts across the higher
terrain of the northern Idaho, northwestern and southern Montana,
and northwestern Wyoming ranges.  WPC probabilities indicate at
least a moderate risk (40 percent or greater) for snow
accumulations of 4 inches or more across parts of those areas. 
Meanwhile, continued onshore flow with embedded energy aloft will
support additional snow, with locally heavy accumulations across
the northern Cascades.  Snow levels will remain low enough to
support at least a few inches at the pass level, with WPC
probabilities indicating at least a slight risk (10 percent or
greater) for additional accumulations of 4 inches or more at both
Snoqualamie and Stevens passes.

By late tomorrow the upper trough is expected to shift east over
the Rockies.  Models show a split in the flow beginning to
develop, with an upper jet couplet centered over the central
Rockies.  The associated upper level forcing combined with upslope
flow and low-to-mid level frontogenesis will support snow
developing over the central Rockies beginning Wednesday.  The
southern branch of the upper trough is expected to amplify, with
northeasterly flow increasing on the northwest side of a deepening
surface low over the Texas Panhandle.  This will support snow
developing east of the Front Range onto the Palmer Divide
Wednesday night into Thursday morning.  From the Front Range to
the Sangre de Cristo Mountains and onto the Palmer Divide, WPC
probabilities indicate that accumulations of 4-8 inches are
likely, with a significant threat for locally heavier amounts
especially along the Front Range.  The heaviest amounts are
expected to fall west of the I-25 corridor, although portions of
the western Denver Metro may be impacted. 

For Days 1-3, the probability for receiving at least 0.1" of
freezing rain is less than 10 percent across the lower 48.

Pereira