What creates freezing rain conditions vs. snow?



Hello from Central TX! A few weeks ago, we got tons of pillowy, perfect snow for the 1st time in my life.

This weekend, we are getting dangerous freezing rain. What conditions create freezing rain instead of wonderful snow?

In: Physics

Freezing rain is caused when snow falls through a large pocket of warm air on the way down. This melts the ice crystals a bit, but when they return to colder air they’ll freeze up again. Sleet is caused the same way, just with a smaller pocket of warm air.

Freezing rain is when rain is supercooled so that it freezes immediately when it his a surface. Everything gets coated with a layer of ice. Not nearly as much fun as snow 🙂

The lower atmosphere changes temperature rapidly with height, sometimes it’ll act as a “sandwich” where there’s two very cold layers with a warm layer in the middle. We call this a “warm nose”. How deep it is changes the precipitation type. If it extends almost to the ground then you end up with frozen rain because the snow doesn’t have time to refreeze after it melts in the warm nose, however the ground it still below freezing so the water freezes as soon as it comes into contact with a surface. If the warm nose is shallow then sometimes the snow doesn’t melt fully and you get sleet or slushy snow on the ground.

Along with what others have said. You can have above freezing temps for rain like 35 or 36 F and get a bunch of rain. Then while the ground and streets are still very wet from the recent rain you have a sudden plunge in temp within a few hours. Like from 35 to 20. Resulting in all that water covering everything suddenly freezing. Coating quite literally everything in a sheet of ice.

The nastiest is when the ground is below the freezing temperature of water but the air is above the freezing temperature of water. It rains and then freezes to the ground.