Rime is created by supercooled water droplets that freeze on contact with surfaces. It is pretty common in mountains because of the cold temperatures. At the University of Utah Flight Park South weather station, we replaced a precipitation sensor, and saw a lot of riming on the fence and all the weather instruments.
Wednesday, December 18, 2013
Freezing rain is a pretty rare occurrence in Utah. We had an event in January which gave everyone trouble. And here we are again with another event likely to happen.
This morning's sounding (data from a weather balloon) from the Salt Lake International Airport shows the surface is really cold and the air above us is warm. This is called an inversion.
The inversion is partly responsible for the poor air quality right now, shown below...
If you take a look outside, you can't see much of the valley...
This storm will help clear this out.
The Thursday morning the NAM shows a pressure trough approaching Utah bringing moisture. We're expected to get precipitation out of this shown in the bottom right panel. But the temperatures at 700mb (about at the top of the mountains) is above freezing. The falling snow will melt in the warm layer, and freeze on contact with the surface in our cold valley. This will create some slippery roads, so be careful!