A rare weather phenomenon took place this morning near Great Falls. What was it?

Early this morning a rare weather phenomenon took place just south of Great Falls.  It's called thundersnow.  It was snowing and lightning at the same time.

How rare is it? 

It reportedly only happens about six times a year on average around the world.

Robert Hart of the Great Falls National Weather Service Office says it ocurred over Helena and White Sulphur Springs.  Helena got a small amount of snow, but Hart says White Sulphur Springs got over an inch.  He says, in all there were about eight lightning strikes.  In Montana Hart says it may only happen once every few years.

What causes it?

Thundersnow is caused often near mountains where the winds go up the mountains and some warmer air mixes with the cold.  Hart called it a very special combination of events that have to occur at the same time for thundersnow to be created.

According to Treehugger.com  the most common places to see thundersnow is in  Montana,  Wolf Creek Pass in Colorado and along the shores of Lake Ontario.  One of the last times it occured in Montana, according to reports is back in 2017 in Whitefish.

In February of 2014,  Chicago was hit with a rare thundersnow storm and in a matter of an hour about eight inches of snow fell.  Wolf Creek Pass, Colorado had 41 thundersnow storms over the winter of 2004-05 and 2005-06.  That is extremely rare.

Hart says people that experienced today's storm in Montana had to be shocked to hear the thunder booms.  They probably wondered what the heck was going on.