Forecasters warn that the frozen precipitation could cause hazardous driving conditions during Tuesday morning's commute along the Interstate 5 corridor.
The low temperatures early Monday included 24 at Sea-Tac Airport, 17 in Olympia, 7 in Spokane, 3 in Yakima and zero at Pullman.
Clouds increased over the Western Washington on Sunday night and Monday morning as a weak onshore flow started pushing warmer and moister Pacific air over the top of the cold air mass that's currently in place.
This process will continue Monday and Monday night with light snow at times over all areas except right along the coast by Monday afternoon, forecasters say.
The warm air will slowly erode the cold air mass over the region Monday night into Tuesday night. As this happens the precipitation will change over from light snow to light drizzle, with the possibility of some freezing drizzle during the transition.
This change-over in precipitation type will begin along the coast later Monday into Monday night then spread over the interior from south to north during the day on Tuesday into Tuesday evening.
Precipitation amounts are expected to be light, with accumulations of less than an inch are possible over most of the area through Tuesday. But even light amounts of freezing drizzle can cause hazardous conditions on untreated roadways and sidewalks.
The cold air mass should be completely eroded by Tuesday evening, ending the threat of freezing and frozen precipitation over the lowlands.
This is a developing news story. More information will be posted as it becomes available.