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Orographic Lift Helps Produce Surprise Snow

By Chris Spears

SILVERTHORNE, Colo. (CBS4)– Mountain commuters were caught off guard early Tuesday as overnight snow snarled the morning commute in and around the Eisenhower and Johnson tunnels.

The snow was caused by powerful west winds blowing perpendicular into the heart of the Rocky Mountains, creating an upslope flow of air that produced widespread cloud cover along and west of the Continental Divide.

(credit: CBS)

(credit: CBS)

Because the atmosphere was fairly dry most locations only saw scattered light snow showers that didn’t amount to much.

But in the case of Interstate 70 around the tunnels the terrain helped focus the flow of wind in a process called orographic lift, where air is forced to rise even higher into the atmosphere, cooling and condensing into clouds. This process can produce localized areas of enhanced wind and snow, much like we saw early Tuesday.

(credit: CBS)

(credit: CBS)

Colorado’s Continental Divide is famous for enhancing the flow of our atmosphere and creating areas where the weather can be more extreme than locations nearby. It’s something that we as forecasters know can happen, but due to the complexity of Earth’s lower atmosphere, it can be tough to forecast exactly when and where those heavier bursts might occur.

(credit: CBS)

(credit: CBS)

It’s a good reminder to always be prepared for any type of weather when traveling into the high country.

Meteorologist Chris Spears writes about stories related to weather and climate in Colorado. Check out his bio, connect with him on Facebook or follow him on Twitter @ChrisCBS4.


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