Weather Words: Overrunning

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Winter is overrunning its welcome, quite literally. As back-to-back storms take over the northern tier, overrunning is playing a big role in turning everything into a slippery mess, with Winter Storm Freya leading the charge.

Overrunning occurs when a warmer air mass “runs into” colder air and is forced up and over the colder air mass. Cold air is denser than warm air, so that’s what forces the warmer air up. Many times this occurs when there is a warm front pushing northward into colder air, so the warmer air associated with the warm front rises above the cold air mass.

When this occurs in the context of a winter storm, it can make for an icy mess.

Freezing rain is what turns everything into an ice skating rink. Roads, bridges, cars, powerlines, everything is encased in ice. This not only leads to impossible travel conditions (yes, even for northerners who are used to winter weather), but it can also lead to downed trees and power lines which results in power outages.

Make sure you check the forecast and stay up to date on the evolving situation when it comes to the potential for winter weather. And stay off the roads if your area has the chance of icy conditions.

J​ennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.