Winter Weather — San Juan, Washington

2020-12-21 · San Juan, Washington

Event narrative

A strong cold frontal passage brought a changeover from rain to wet, dense snow during the afternoon hours on December 21. These conditions led to a quick accumulation of generally 1-2 inches of snow (with an isolated report of 5 inches) that covered grassy surfaces and some roadways, leading to hazardous travel conditions.

Wider weather episode

A strong cold front moved through Western Washington through the day on December 21. After a morning of fairly mild conditions, temperatures and snow levels drastically dropped in the wake of the front, with rain changing to dense, wet snow and quickly accumulating on roads and grassy surfaces. Lowland areas across far northern portions of Western Washington (Western Whatcom County, the San Juan Islands, and Clallam Counties) received between 2-4 inches of snow in a short period of time. Road conditions rapidly deteriorated across the county, including portions of I-5 north of Ferndale in Whatcom County.

Source: NOAA Storm Events Database, event_id 934870. Narrative written by the NWS forecast office that issued the report.