Why so cloudy?

Jan. 31, 2017: Sunshine is in the forecast! Not just a few glimpses, either. By the end of the work week, the sky should be mostly sunny for a short stretch.

sunny outlook

 

The trade off: the weather gets colder. The colder air is drier, helping get rid of any extra moisture to help make clouds.

Midwest RPM 4km Hi-Res with fronts

The colder air helps get rid of one of the main mechanisms for creating all of the cloudy weather over the last few weeks: a temperature inversion. WARNING: there’s a lot of science ahead!

A temperature inversion is when a layer of colder air gets trapped under a layer of warmer air.

temperature inversion

 

Remember: warm air rises, cold air sinks. Under this setup, the cold, dense air near the surface doesn’t want to rise too far, since it’s colder than the air around it. We’d have to either warm up the lower layer of air a lot until it’s warm enough to rise past the upper layer, or we get the upper layer cold enough that the lower layer can rise as well.

temperature inversion1

Where do the clouds come in? As the lower layer starts to heat up, it rises like warm air likes to do. However, it can only go so far before it hits the “lid” of warmer air over top of it. Clouds form right where the “lid” is, and can get “trapped” there, since the lower layer isn’t getting much warmer. As long as the inversion is in place, the weather remains mostly cloudy like we saw over the last few weeks.

temperature inversion2

Not helping was all of the melting snow recently. This adds moisture to the air, creating more clouds and fog that don’t want to clear out.

In the case of this week, the air gets back to its “usual” set up (getting colder as you rise through the atmosphere) with a new round of colder air sliding in. That gets rid of the clouds, brings back the sun, yet drops our temperature for a few days.

Ok, that was a lot of science. Comment on our Facebook page or email me at akirchner@wrex.com if you have any questions!

-Alex

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Posted under weather

This post was written by Alex Kirchner on January 31, 2017

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