Air quality dropping with smoke, haze building in some areas, thunderstorms in mountains

A weak upper-level disturbance is causing winds to shift and bringing smoke aloft in some parts of western Washington.

Some of that smoke is mixing down to lower levels, causing the air quality to drop and turn smoky around the South Sound and Bellingham.

It should worsen over downtown Seattle as well through the day Thursday.

That same disturbance is helping generate thunderstorms in the mountains.

East of the Cascades, poor air quality and wildfire smoke will continue to produce thick haze and potentially hazardous conditions.

Daily afternoon mountain thunderstorms with fires and smoke near and east of the Cascade crest will be the pattern through at least the first part of the weekend.

Then, hopefully, we can phase out the mountain thunderstorms—which carry a significant risk of starting more fires.

Unfortunately, mountain thunderstorms will erupt again Thursday, beginning around 11 a.m. and lingering through sunset.

Higher-elevation locations like Hurricane Ridge, Washington Pass, Diablo Lake, Ross Lake, Stevens and Snoqualmie passes, and Mount Rainier are all fair game.

This is another high-risk situation for new fire starts, prompting Red Flag Warnings. A similar setup is expected Friday.

The very weak upper-level disturbance is a trough—not strong enough to bring rain to the Puget Sound lowlands, but enough to help trigger thunderstorms over the mountains.

Think of it as providing an extra nudge of lift: slightly unstable air is forced upward over the terrain, and with daytime heating, that can be enough to spark thunderstorms.

This trough is a slow mover, but by Sunday it shows signs of weakening and shifting southeast. That should gradually quiet the higher-elevation thunderstorms Sunday into Monday.

Seattle’s weather stays quiet through the weekend and beyond.

Morning clouds and afternoon sunshine will be a familiar daily routine for the city until further notice.