Milwaukee thundersnow reports; what causes the unique phenomenon?

Heavy rain and heavy snow Thursday morning, Feb. 9

There have been multiple reports of people hearing thunder while heavy snow was occurring Thursday, Feb. 9. Were they making it up? Nope! It's a very real and unique weather phenomenon.

All day, we've had periods of heavy rain and impressive snow bands. At times, flakes have been nearly the size of quarters as the moist air is tossed around in the upper atmosphere. All those flakes create a small electrical charge. Those charges, interacting and combined across an entire cloud with millions of other flakes, can create lightning.  

What makes this system unique is just how close we are to being stuck with rain. Temperatures are in the mid to upper 30s, yet we're still getting snow mostly just because of how heavy the rates are and how quickly it falls to the ground. 

On & off heavy snow lasting into Thursday afternoon, Feb. 9

High levels of moisture and rapidly rising air creates similar conditions to what we see in a spring thunderstorm just in colder than-normal conditions. Thundersnow is often associated with very heavy snow rates and quick accumulations which is what we have in our northwestern counties. It doesn't happen often, so when every you hear thunder while snowing it's definitely worth a "What the heck!?"