La Plata County residents who saw rosy pink and cantaloupe-colored flashes inside Monday’s snowstorm need not worry about calling their eye doctors in a panic. What was witnessed was a phenomena experts at the National Weather Service call “thundersnow.”
“It happens when light reflects off ice crystals,” said NWS meteorologist Erin Walter. “It can give off pink and orange hues.”
Regular thunderstorms are caused by three key factors: moisture, a front caused by heating or cooling, and atmospheric instability. According to the NWS website, when an atmosphere is unstable, air near the ground can become buoyant and rise rapidly through the atmosphere. Warm air mixing with cold air is one of the reasons lightning strikes often occur during spring and summer months.
“Air parcels can rise quickly and collide, creating an electrical charge or exchange,” Walter said. “That can create an unstable atmosphere and thunderstorm.”
An unstable atmosphere is also needed to create “thundersnow,” a phenomena that was little understood until about 20 years ago, when new technology helped weather experts better understand what was occurring inside the electrically charged snowstorm.
The warm surface air needed to produce a thunderstorm is the reason a “thundersnow” effect is so uncommon during the winter months. Luckily for those in the Durango area, warm weather conditions colliding with the incoming storm front on Monday created just the right conditions for the phenomena.
“Southwest Colorado had that unstable weather system,” Walter said. “The area got that clash of warm air with a strong low front.”
Walter said the pink- and orange-hued bursts of lightening are caused by the snow.
“Usually you have rain that the light refracts off, but in a snowstorm, the light is refracting and spreading out off the snow,” she said. “It’s a different scatter when you have crystal particles instead of water.”
Walter said those in La Plata County who missed Monday’s show may have another chance late Tuesday.
“We have another snowstorm coming in and we have a pretty unstable atmosphere setting up in that area,” she said. “I would say there is going to be similar thunder and lightning closer to midnight. People may be able to see that same pink lightning phenomena again.”