Where the front comes from is important

This week is a great case in point of how different cold fronts can be. As I write this, we're feeling the effects of a front that moved through on Sunday. Winds have been breezy, skies clear and temperatures 20 degrees cooler than 24 hours ago.

In contrast, another front will move through on Wednesday (later), bringing cooler air again, but also clouds and a better chance for showers. They're both cold fronts, and the difference is where they formed.

A quick definition to get us rolling...a front is a boundary between large areas of the atmosphere with different temperatures, densities and humidities. The front is the leading edge of this large area of air with consistent temperature, density and humidity throughout.

The front that moved through on Sunday formed over land in northern Canada, therefore it brought cold and dry air.

In contrast, the air that's moving in behind the front later Wednesday formed over the Gulf of Alaska. It's cold and wet, and that's what we get on Thursday.

To be a bit more technical, air that forms over land is classified "continental", if over water, then "maritime".

There are different terms that describe its temperature, ranging from tropical to arctic.

The air that's over southern Colorado at the moment is "continental polar". The change that's on the way is "maritime polar".

(One other major contributor to our weather here in Colorado is "maritime tropical" air, which is warm, full of water, and comes in either from the Gulf of Mexico or the southeastern Pacific).