Watch the mountains create their own weather patterns

Towering cumulonimbus clouds form over the Cascade Mountains on Aug. 4, 2013. (Photo:

It's been blazingly sunny in the lowlands for the most part this summer, but those hiking in the Cascades have probably noticed at times a few more clouds around than when they left Seattle.

On Sunday, it was particularly noteworthy as some lingering unstable air from Friday's trough of low pressure brought conditions ripe for thunderstorms in the mountains.

But why there and not here? The mountainous topography is the key. As air flows over the mountains, the lift the hills provide is the key trigger to start the process of creating tall cumulonimbus clouds that eventually become showers and thunderstorms.

You can watch the process play out from Greg Johnson's camera at

But it's not always showers and thunderstorms. Check out this video from Don Jensen who was up at Mt. Rainier during a weekend in mid-July and captured all sorts of interesting cloud patters around the mountains, including the opposite pattern when the lowland are socked in with a marine layer but he was above the clouds at 7,200 feet.