"Snow devil" seen on New Hampshire's Mount Washington. Here's how they form.
A summit crew heading down Mount Washington in New Hampshire saw a rare weather phenomenon known as a "snow devil" on Wednesday.
Researchers with the Mount Washington Observatory captured a photo of the "long, well-developed snow whirl" and shared it to social media.
"They sat and watched as it traveled down the mountain and crossed the road," the observatory wrote.
How do snow devils form?
Similar to a dust devil, a snow devil is created by wind shear - winds blowing in opposite directions near the ground level of the atmosphere.
Conditions were just right for observers on Wednesday. The winds picked the snow up off the ground and lifted it into the air, swirling it in opposite directions creating a mini vortex.
Snow devils are much more rare than dust devils due to the conditions needed for formation.
Dust devils typically occur due to differential surface heating, generally in warm climates. That causes air and dust to rise, which in combination with winds blowing in different directions, causes the vortex.
Climates like Mount Washington's are much colder and typically do not experience much differential heating over small areas. Depending on the nature of the snowpack, it can also be difficult to pick the top layer of snow off the ground.
Mount Washington summit forecast
The Mount Washington Auto Road, which is currently closed for spring clearing, posted on Facebook that 8 inches of snow fell on the mountain Tuesday night, and that was followed by wind gusts of up to 79 mph that blew snow drifts around the road.
"With the recently fallen snow, it's no surprise that today's breeze has kicked up some snow, and this whirl was particularly visible against mostly clear skies," the observatory said.
The higher summits forecast for the observatory says fairweather skies on Thursday will give way to clouds and bring light snow showers for Friday. Temperatures will be in the 20s with winds gusting up to 50 mph on Thursday night.
Back in February, the observatory recorded a wind gust of 161 mph, the strongest seen on the summit since 2019.
