Why freezing rain is Texas' most common winter precipitation

Snow is not common in Central Texas, but freezing rain is. This week marks the third freezing rain event just this year. And it’s all because of Texas’ geography, both its terrain and location. 

Texas sits at the southern end of the great plains. That means that there is no topographical boundary between us and the North Pole- just flat grasslands all the way to the arctic. The lack of mountains means that cold air isn’t blocked when it starts to move south, all the way to the Gulf of Mexico. 

The Gulf of Mexico is the second part of the equation. It is, of course, the southeastern border of Texas and is a massive subtropical body of water. That means the water temperature never really drops below 60 degrees. There is also no mountain range between the Gulf of Mexico and Texas, so the warm humid air is free to move throughout the state as it wants. When the cold arctic air meets the very warm subtropical air, things can get interesting. 

A basic tenant of meteorology is that cold air is denser than warm air. That means that warm air will "float" on top of cold air. Texas frequently sees cold air move in from the north at the same time warm air is trying to move in from the south. The cold air forces the warm air to float on top. This is referred to as a "warm nose" and is very important for freezing rain. 

With a warm nose in place any precipitation will melt on the way down, but encounter much colder temperatures right above the surface.  If surface temperatures are below freezing, the rain will freeze on contact with the ground.   

So, Texas is perfectly placed to get very cold air from the north as well as very warm air from the south. Arctic airmasses from the north can easily undercut the subtropical airmasses from the Gulf of Mexico. And with shallow layers of arctic air, any precipitation that falls is basically guaranteed to be liquid as it falls into the very cold air at the surface.

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