The National Weather Service (NWS) in Seattle has issued an air stagnation advisory, which is in effect until noon Monday, December 11th.
“Dry conditions, light winds and poor mixing has lead to stagnant conditions in the interior lowlands. Stagnant conditions may trap pollutants near the surface which may lead to deteriorating air quality,” the advisory said.
A strong upper ridge, responsible for the recent sunny days across Western Washington, is expected to stick around through the end of next week. NWS forecasters say inversions will keep temperatures cooler in the lowlands while temperatures will be warmer in higher elevations (e.g. 54° at Mt Baker while 37° in Ferndale at 4:45pm today).
Fog and freezing fog will expand in coverage and duration on Saturday according to forecasters.