There have been many mentions this week of “Thundersnow” a phrase which covers a thunderstorm when it’s snowing. Both these types of weather cause great excitement for people in the UK. Our up/down will it /won’t it winters, hyping us all into a frenzy when snow is eventually forecast. Alongside the power of thunderstorms, the crash and bang, mighty rumbles and huge forks of lightning.
So, the combination is bound to be impressive. I wasn’t really convinced “thundersnow “ was a real thing, it seemed more like a made-up phrase to give an unusual weather phenomenon a headline, or this year, a hashtag.
Snow showers are convective, created by upward motion of the air, with a warm source below. Rain showers can grow into thunderstorms, and snow showers can be accompanied by thunder and lightning.
What you need is a cold air mass travelling over a relatively warmer sea. The sea warms the air by the surface which starts the overturning, the Cumulus clouds begin and then can grow into Cumulonimbus clouds and produce the thunderstorms. As the hefty showers near land and the warmer source is replaced by colder land, often hills, we see the showers producing snow.
Spectacular sight-seeing lightning reflect off a thick, glistening, layer of fresh snow, in the darkness!
Reports say that the sound of the thunder is dampened by the snow on the ground and in the air. So, a rumble of thunder can just surprise you suddenly as there isn’t the usual long distance build up getting closer. That would make more of an impression on anyone.
Also in the dark the lightning can be reflected off the white snowflakes, creating strange effects and making the light of the strikes even more vivid.
A few of our Netweather forum member’s experiences
Most memorable was during a heavy fall in the 2010 snow. I was watching it out the window which overlooks onto the farmland and countryside beyond and the whole sky lit up and it was so bright where it reflected off the snow. It was like someone had turned the light on a winter scene.
The lightning was glowing purple and the thunder acoustics were very strange due to the snow falling too.
Personally, I've seen thundersnow only once. On the evening of 25 January 2013, I saw a huge flash of light and then a deep rumble of thunder during a snowstorm, from my home in Manchester. However, there was only one lightning strike. There we also some huge snowflakes too, some maybe 5cm in diameter!