Breaking down precipitation types during the winter months
QUAD CITIES, Iowa/Ill. (KWQC) - Whether it’s rain, freezing rain, sleet or snow, we tend to see it all during the winter months in eastern Iowa and western Illinois.
But what exactly are the differences between all of them?
It all has to do with the temperatures at different levels in the atmosphere.
It’s important to note that temperatures cool down as you go up in the atmosphere.
When clouds form, water vapor condenses onto tiny particles within the cloud, known as cloud condensation nuclei. This leads to the development of ice crystals which is why all precipitation starts out as snow.
As the snow falls trough warmer air, it melts and as long as the entire layer of air to the ground is above 32°, the precipitation will stay in the form of rain.
If there is a shallow layer of below freezing temperatures on the ground, the rain does not have time to switch over to snow or sleet, so it falls as rain but freezes on contact. This is known as freezing rain.
It is possible to have freezing rain with temperatures in the 20s, as long as there is a deep enough layer of above freezing temperatures several thousand feet above the ground.
Sleet forms when the snow falls through a shallow layer of warm air, melts to rain, but then re-freezes to ice pellets with a thicker layer of colder air from the mid to lower levels of the atmosphere, to the surface.
If the entire column of air is below 32°, the precipitation stays as snow.
The highest threat of freezing rain on Feb. 22 is north of the Quad Cities, between the Highway 30 and Highway 20 corridors (north of Clinton and Savanna). Click here for the latest First Alert Forecast.
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