Weather Blog

Why you don't see Eastern Wash. wildfire plumes until the afternoon

Why you don't see Eastern Wash. wildfire plumes until the afternoon
Video from Air 4 shows a smoke plume rising from the Chiwaukum Fire Complex on July 30, 2014.

Local social media posts have been perking up each afternoon noting tall plumes of clouds over the Cascades. What you're seeing are smoke and the "pyrocumulus" clouds created by the wildfires burning in Eastern Washington. The heat from the fires is its own engine for creating rising air that cools and condenses into clouds.

But why don't we normally see those clouds over here until the afternoon?

There is a bit of an inversion in play in Eastern Washington, caused by sinking air aloft from high pressure and cooler air forming near the ground at night from clear skies allowing the day's heat to radiate back into space.

The morning weather balloon launched in Spokane Wednesday showed the temperature at the surface was 63 but was a whopping 84 degrees at 3,000 feet. It was a little warmer in Central Washington near the wildfires this morning, but you get the idea.

But as the day -- and the ground -- warms up, eventually this process reverses and the lid goes 'poof' allowing the hot air and smoke to roar to the skies, creating a vertical plume visible across much of the state.

Here is a video that shows a great example of how this happens. This was time lapse video shot from Silverdale of a small wildfire that was burning in the Olympic Mountains in September 2011.

I've set this video to start around 1 p.m. and if you look close, you can see a time stamp in the upper left corner, but 2 p.m. happens at the 0:35 second mark of the video and...it's real obvious when that inversion breaks:



So that's why we're not seeing the smoke plumes as much in the mornings as we do in the afternoon over here in Western Washington -- have to wait for the inversion to break.