Climate change likely to transform snowfall in NoCo

The snow pattern that’s plopped more than 2 feet of flakes on Fort Collins in as many months is a preview of what climate change might have in store for Northern Colorado.

As temperatures climb in the coming decades, it’s likely the next generation won’t see the late fall and mid-spring snow storms that seasoned Coloradans have come to love and loathe. Instead, snow will be more likely to fall in the mid-winter months of December and January, like it has this season.

It’s a multi-faceted phenomenon that would change the face of winter in the region. Colorado state climatologist Nolan Doesken laid it all out with a lone caveat: Nothing is certain in climatology.

If you’ve lived in Northern Colorado long enough, you already know the snow season here is an extended, director's cut version of what most of the country experiences.

“We have practically a 9-month snowfall season in Fort Collins, historically,” Doesken said. “We’ve had snow as early as early September and as late as early June.”

During the last three decades, Fort Collins has received nearly an inch of snow on average in September and 3.6 inches in October, according to data from Colorado State University's Colorado Climate Center. And the snow keeps falling well into the spring, with an average of 6.2 inches in April and 0.7 inches in May.

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The strange thing about snow in Fort Collins is that most of it comes in fall and spring rather than winter months. We receive about 33 inches combined during the months of September, October, November, March, April and May.

December, January and February account for a total of about 23 inches.

Northern Colorado gets snow earlier and later than other parts of the country in part because of its high elevation, which keeps temperatures chilly enough for snow. But as temperatures drop in mid-winter, the air is too cold to cling to the moisture needed for snow.

What’s more, Fort Collins’ location downwind of the Front Range puts it in a less likely spot for mid-winter snows. The jet stream that delivers moisture from the Pacific Ocean to the western U.S. must leap across myriad mountain ranges before it gets to the final barrier of the Front Range.

“Whatever moisture is left is usually evaporating and diminishing as it comes out on the Great Plains, which is why some of the driest parts of the country in mid-winter are on the downwind side of the Rockies,” Doesken said.

STREETS:  Crews work to clear excess snow buildup

So what does global warming mean for snow in Northern Colorado?

Climatologists aren’t exactly sure how climate change will affect precipitation, but we’re already seeing its effects on temperature. And warmer temperatures will change the way we experience snow here.

Warmer weather in fall and spring months will turn more of those off-season snows into rain. Many fall and spring snows come when temperatures are in the upper 20s and low 30s, barely cold enough for snow. So a small change in temperature could make a big difference.

Fort Collins already saw something like this in November, when the area got just shy of an inch of rain during the first week of the month.

“We’d never recorded a rain that big in early November that hadn’t – at least at the end – changed over to snow,” Doesken said. “That was one example of a storm that might have been affected by warmer temperatures. That was sort of a big deal.”

By the same logic, December, January and early February are likely to see more snow in Northern Colorado because of climate change.

Even a large increase in temperature would keep Northern Colorado plenty cold enough for snow. Slightly warmer mid-winter temperatures would actually be preferable because the warmer air would hold more moisture.

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And warmer Arctic Ocean temperatures would lessen the temperature gradient between the Arctic and the Equator, which could weaken the force of the jet stream that carries moisture across the Front Range. A weaker downslope flow heading down the mountains could potentially mean more moisture to spare for Northern Colorado, Doesken said.

If all this comes to fruition – Doesken’s thinking about 2040 or 2050 – Fort Collins’ total snowfall would likely remain close to the current average of 50 to 60 inches per season. The snow would just be dispersed differently, Doesken said.

Like now, the snow that falls early or late in the snow season will be prone to a swift melt, while mid-winter snows will continue to cling to the ground for longer periods.

One thing you can bank on is that Fort Collins winters will remain white.

Reporter Jacy Marmaduke covers environment and breaking news for the Coloradoan. Follow her on Twitter at @jacymarmaduke .

Average snowfall in Fort Collins by month, 1981-2010

September: 0.9 inches

October: 3.6 inches

November: 8.6 inches

December: 8.4 inches

January: 7.9 inches

February: 6.9 inches

March 12.6 inches

April: 6.2 inches

May: 0.7 inches

Snowfall recorded in Fort Collins by month, 2015-2016:

September 2015: None

October 2015: None

November 2015: 8.4 inches

December 2015: 16.7 inches

January 2016: 7.9 inches (as of Jan. 10)