The National Weather Service said visibility early Wednesday morning in the central Puget Sound area was a quarter-mile or less.
The high pressure has created a condition where the coast and mountains are sometimes more likely to see sunshine than lowlands and valleys.
Forecasters often forecast afternoon clearing in gloomy areas, but some days the clouds never lift.
Forecasters said Washington's foggy weather is likely to persist through the weekend with a change possible by Monday to colder weather and clearing, but still dry.
More Northwest Headlines
Southwest Oregon wildfire grows to 23 square miles 3:22 p.m. State senators question deal limiting shoreline development 3:22 p.m. New fishing restrictions off Neah Bay begin 3:22 p.m. Central Washington wildfire grows to more than 9 square miles 3:22 p.m. Man attacked by bear at Joint Base Lewis-McChord More than 350 people evacuated as Lake Chelan wildfire grows Tourists flock to gawk at highway projects such as Seattle’s floating bridge Kitsap sewage spill prompts warning to stay out of water
Our new comment system is not supported in IE 7. Please upgrade your browser here.