A strong upper level ridge will keep a dry stable air mass over Western Washington through at least Thursday. Weak low level onshore flow has brought cleaner marine air to the coast and areas near the Strait of Juan de Fuca. For the interior lowlands of Western Washington, however, air quality has gradually deteriorated since Sunday and many sensors are now reporting marginal to poor air quality. 

Northerly flow aloft will continue to transport smoke into Western Washington from wildfires in British Columbia through at least Wednesday. In addition, atmospheric ventilation in the interior lowlands of Western Washington will remain poor. Weak low level onshore flow will continue to bring better air quality to the coast and areas along the Strait of Juan de Fuca. 

The smoke and hazy skies will continue to plague Western Washington for the next few days. A change to southwest flow aloft late Thursday could start to push the smoke out of the area.