Why Vermont is getting more heavy, wet snow storms

The storm that hit Vermont early Monday morning left well over 8 inches of snow in several towns and more than 35,000 homes without power.

It was one of the most damaging to the state’s power grid in recent history — causing the fifth most customer outages at the peak of the storm since 2009, according to data from VT Outages.

The damage to power lines came from heavy, wet snow, weather that’s becoming increasingly common as climate change brings warmer winters and more extreme precipitation to the region.

“When you put those two together, you get more wet snow,” said meteorologist Jason Shafer, the chief science officer at Disaster Tech.

He said the state still gets intense cold temperatures and dry snow, but those conditions are less reliable than they once were.

“You just are more likely to have wet snowfall, even during the middle of winter," Shafer said. "The evidence for this is — you don't need to look too far, you just look at the recent storm history."

Storms in December of last year and March 2023 knocked out power for over 50,000 homes and nearly 40,000, respectively. Those storms cost Green Mountain Power over $13 million each to repair damages, according to filings with the Vermont Public Utility Commission.

"Those all have their fingerprint on the [wet snow] season widening," Shafer said. "Unfortunately, that's just our future that we're in right now."

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Wet, heavy snow is largely a result of higher temperature and humidity. Heavy snow has a higher water content, sometimes called a snow to liquid ratio. A wet snowflake can be partially melted while its falling, and has water on its edges that make it stickier.

"That stickiness can cause it to stick onto trees and powerlines and cause problems," Shafer said. "Whereas a dry snow is going to fall at much colder temperatures and that is going to just fluff off of everything and be what we call 'Chamber of Commerce snow,' the kind of powdery snow that we love for for skiing and and recreating."

Wet snowfall can also be difficult to predict. When temperatures are right around freezing, a change of a few degrees can mean the difference between rain or snow. And if you get enough snow, it can actually cool the atmosphere.

"Much like if you put an ice cube in your drink, it would cool the drink," Shafer said. He added that in the case of the storm this week, it snowed more at lower elevations than predicted because of this cooling effect.

Shafer said his forecasts on Sunday had shown about a 5% chance of a storm with widespread outages developing. He woke up in the middle of the night when his power flickered at his home in Danville.

"I emailed our customers between 2 and 3 in the morning, because I was like, 'Oh sh—, here it is.'"

Later he told Vermont utilities, "this is the poorest detection of a major wet snow storm in the last 10 years."

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Lexi Krupp is a corps member with Report for America, a nonprofit national service program that places journalists in local newsrooms to report on under-covered issues and regions.