Ice Storm in Seattle and Vicinity, Washington

Significant ice accumulation was reported form multiple sources during the morning hours of Dec 23. SeaTac airport reported around 0.20 inches of freezing rain by 8am on the 23rd. Other reports included: 0.25 inches in Des Moines, 0.13 inches at the NWS Seattle Office, 0.25 inches in Kenmore, 0.20 inches in Renton, and 0.13 inches in Mountlake Terrace. The highest amounts were reported from West Seattle at 0.3 inches, 0.3 inches in Federal Way, and 1 mile west of SeaTac at 0.4 inches.

After a series of snow events in the lowlands and mountains of western Washington, a system off the Pacific brought a modifying airmass towards the area right before the Christmas holiday. Warmer Pacific air was able to overrun lingering cold air very near the surface, producing a warm layer of classic characteristic of a freezing rain profile. As such, measurable ice accumulation led to hazardous impacts across the area, most noticeably to roadways and travel.