So, you find out that thunder snow is in your forecast - a term you are not familiar with - so off to the internet you go to do some research. Just the right conditions have to exist for this weather phenomenon to occur, but it is exciting, to watch, even if you aren't a kid.
What is Thunder Snow?
It is defined as a thunderstorm with a brief heavy snow instead of rain.
Patrick Market, Associate Professor of Atmospheric Science at the University of Missouri in Columbia, states "thundersnow starts out like a summer thunderstorm, the sun heats the ground and pushes masses of warm, moist air upward, creating unstable air columns.
As it rises, the moisture condenses to form clouds, which are jostled by internal turbulence.
The "tricky part" for making thundersnow, Market said, is creating that atmospheric instability in the wintertime.
For thundersnow to occur, the air layer closer to the ground has to be warmer than the layers above, but still cold enough to create snow—a very precise circumstance."
In the recent southern U.S. thundersnow storms, for instance, the atmosphere became unstable enough that thunderstorms with rain developed. Those storms then moved north where the air was below freezing, said Howard Silverman, a National Weather Service senior forecaster in Sterling, Virginia.
The thundersnow events were also coupled with "pretty decent snowfall rates," at the rapid clip of more than two inches (five centimeters) an hour, Silverman said.
Thunder Storm Facts
There are usually four forms of thundersnow:
A common thunderstorm on the leading edge of front that runs into a front of the opposite temperature and where the precipitation takes the form of snow.
A heavy, large-scale snowstorm that sustains strong upward mixing with cyclonic winds which allows for favorable conditions for lightning and thunder to occur.
A lake effect or ocean effect thunderstorm which is produced by cold air passing over relatively warm water; this commonly produces snow squalls over the Great Lakes.
A cold front containing extremely cold air up high and strong upward air movement from down low which allows for favorable conditions for lightning and thunder to occur.
One unique aspect of thundersnow is that the snowfall acts as an acoustic suppressor of the thunder. The thunder from a typical thunderstorm can be heard many miles away, while the thunder from thundersnow can usually only be heard within a two to three mile radius from the lightning.
When thunder and lighting occur during a snowstorm it most often appears in late winter or early spring. In the United States, March is their peak month of formation, and on average, only 6.3 events are reported per year, so it is pretty rare.
Sounds of Thunder Snow
Market, Patrick S., Chris E. Halcomb, Rebecca L. Ebert, 2002: A Climatology of Thundersnow Events over the Contiguous United States.