Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
310 AM EST Wed Jan 29 2020

Valid 12Z Wed Jan 29 2020 - 12Z Sat Feb 01 2020


Days 1-3...

...Pacific Northwest to Northern Rockies....

An area of precipitation just off the WA coast is set to move
onshore this morning as a combination of enhanced low-mid level
relative humidity and ascent occurs as a mid level trough moves
onshore. 
The wave deamplifies while it moves inland, so while the precip
does move into the northern Rockies, amounts will be light due to
weak ascent as the band of moisture moves across, plus the band of
moisture steadily moves so no one area is within the band for an
extended period.
There is a low to moderate probability of a foot of snow in the WA
Olympics and portions of the northern WA Cascades.  

An upstream system is expected to bring another round of generally
light precipitation across the Northwest and northern Rockies
Thursday.  As with the previous system, widespread heavy amounts
are not expected.  A warm front lifting north along the Washington
coast Thursday evening will bring another round of snow to the
northern WA Cascades.  However, with snow levels on the rise,
heavy accumulations will be mainly confined to the higher
elevations of the northern WA Cascades. Most models keep higher
QPF and snow amounts further north in Vancouver Island/British
Columbia.

For Days 1-3, the probability of significant icing (0.25-inch or
greater) is less than 10 percent.

Petersen