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Warm storms aren’t great for sustaining skiing, snowpack or cloud seeding

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March 3, 2020, 10:29 am

March used to be a heart-of-winter kind of a month in Colorado’s high country, with colder temperatures and tons of fluffy, highly skiable snow throughout the month. Sure, the sun would often shine, but the snowpack didn’t degrade as rapidly as it has in recent years.

Skiing out of Stone Creek on Saturday.

That is an anecdotal observation from someone who’s lived here for nearly three decades. April was always the big spring-skiing month, with warm days, high sun angle and occasional fat, wet storms that melted away quickly. March is looking more like April these days in Colorado.

The most recent forecasts bear that out after a cold and snowy February. Here’s how March is shaping up so far:

“Tuesday through Saturday will be mostly sunny, dry, and warm with high temperatures in the 30s and maybe getting into the 40s on Friday and Saturday,” Opensnow.com meteorologist Joel Gratz wrote Tuesday. “Then we’ll see two chances for snow during the following week. The first system could bring snow from Sun, Mar 8 through Tue, Mar 10. The second system could bring snow from Thu, Mar 12 through Fri, Mar 13. Both storms will be warm.”

That last sentence says it all: “Both storms will be warm.”

A recent study by two U.S. Geological Survey scientists published in the journal Science paints a dire picture for snowpack in the Colorado River basin. Here’s the opening to a story on that study written by Summit County resident Bob Berwyn for InsideClimate News:

“Global warming is shrinking the Rocky Mountain snowpack that feeds the river and flows are declining at a rate of about 9.3 percent for every 1.8 degrees Fahrenheit increase in temperature, according to a new study that ‘identifies a growing potential for severe water shortages in this major basin.’”

A story in Monday’s Vail Daily reports we’re ahead of the curve this ski season in terms of snowpack, but it also notes that can turn around in a hurry.

Last month I wrote a story for the Vail Daily on another recent study definitively proving that cloud seeding – under the right circumstances – can increase the snow output of storms, something the ski industry has known for years. Produced in collaboration with the nonprofit Aspen Journalism organization that focuses on water issues, it was also posted on their website.

Some reporting that didn’t make it into my story: When a storm is actually producing quite nicely on its own, local cloud-seeding generators are shut down for public safety. In other words, even in Colorado ski country, there can be too much of a good thing.

Like, for instance, the storm that turned warm and windy mid-dump and shut down the upper halves of Vail and Beaver Creek on Friday, Feb. 7, in what’s now being called “Snow-pocalypse.” Roads and chairlifts were shut down due to avalanche danger and high winds, while a huge crowd of mostly locals descended following a 17-inch snow report at Vail, where social media photos of epic lift lines went viral and prompted a Vail Resorts’ apology.

It’s also noteworthy that warm storms from the southwest are not ideal for cloud seeding, which is what happened the following weekend in mid-February, and what it sounds like will happen next week in the Vail Valley. Temps in the mid-20s or higher are a little too toasty for cloud seeding.

Finally, I interviewed several scientists and snow-safety experts last spring when big, wet, heavy storms not typically seen historically in the Colorado Rockies in mid-winter destabilized the snowpack to the point that we saw historic slides that came down onto Interstate 70. Rain and wet snow in December, January and February are changing Colorado’s snowpack, they said.

I love warm, sunny Colorado ski days like last Saturday as much as the next guy, but the warmer and sunnier our climate gets, it’s shortening our ski seasons and clearing our snowpack out earlier and earlier, which exacerbates our ongoing drought and increases wildfire danger.

Now here’s a re-post of the cloud-seeding story that ran late last month in the Vail Daily:

Cloud seeding study validates ski industry staple

An innovative new study conducted in Idaho and published on Monday seems to confirm what Vail and other Colorado ski resorts have believed for decades – that “cloud seeding can boost snowfall across a wide area if the atmospheric conditions are favorable.”

“This is a revelation. We can definitely say that cloud seeding enhances snowfall under the right conditions,” said Sarah Tessendorf, a scientist at the National Center for Atmospheric Research (NCAR) in Boulder and co-author of a new paper on the research conducted by scientists from the University of Colorado Boulder and University of Wyoming, among others.

Cloud seeding uses ground-based generators to disperse dust-sized silver iodide particles into clouds so that ice crystals can form on those particles and fall to ground in the form of snow. Scientists, water managers and ski industry executives say it’s precipitation that would otherwise stay in the clouds, so cloud seeding is an environmentally safe way to enhance snowfall.

But the efficiency of cloud seeding has so far been hard to prove. Tessendorf said previous cloud seeding studies were unable to achieve statistically significant results because the natural variability of the weather was too great and demanded a larger sample size than could be reasonably obtained, for financial reasons.

In the winter 2017, the National Science Foundation, which sponsors NCAR, teamed up with the Idaho Power Company to conduct a field study called SNOWIE (Seeded and Natural Orographic Wintertime Clouds — the Idaho Experiment).

SNOWIE used supercomputing technology to develop a new computer model to simulate cloud seeding, as well as new measurement capabilities, such as a high-resolution cloud radar on a Wyoming research aircraft that can see previously invisible cloud features. Researchers also located mobile radars on mountain ridges north of Boise to see clouds not visible to stationary National Weather Service radars that are blocked by the mountains themselves.

The scientists then used airborne seeding instead of ground-based generators because the silver iodide dispersed downwind from the aircraft in a zig-zag pattern, which is a very unnatural pattern for precipitation to form.

That allowed the scientist “to unambiguously detect the impact of cloud seeding in these clouds using the mobile and airborne radars,” Tessendorf said. “This had never been done before. In the three cases we report on, there was negligible natural snow falling, so the zig-zag pattern was able to be detected very clearly and tracked to the ground to quantify the snow reaching the ground due to seeding.”

One of the examples cited in a press release accompanying the study was a cloud-seeding flight on Jan. 19, 2017, that generated snow for 67 minutes, dusting about 900 square miles with a tenth of a millimeter of snow beyond what was falling naturally.

“This was barely enough snow to cling to the researchers’ eyelashes,” the release reads, ‘but it would have stayed in the air if not for cloud seeding.”

“We tracked the seeding plume from the time we put it into the cloud until it generated snow that actually fell onto the ground,” said Katja Friedrich, a University of Colorado Boulder professor and lead author of the new study.

Dave Kanzer, deputy chief engineer for the Colorado River District, helps oversee a system of 25 ground-based cloud-seeding generators in the central Colorado region that includes Grand, Summit, Eagle and parts of Pitkin County. Nearby generators include one atop Arrowhead and another above Camp Hale.

Kanzer said storms from the north and northwest, which tend to be colder, are ideal for cloud seeding, with temperatures in the clouds no higher than 21 degrees Fahrenheit and no lower than 5 degrees Fahrenheit. If the clouds have the right temperature range and the right moisture levels but lack sufficient particles for ice crystals to form, that’s where cloud seeding comes in.

“We take advantage of the first two and we add the proper amount of particulate matter to enhance the snowfall and precipitation … and that accumulates in the snowpack somewhere in the range of between 5 and 15% on a per storm basis when those conditions are met,” Kanzer said. “And that helps to increase the water yield of the snow sheds in the range of 1 to, 4% of water on a seasonal basis.”

The Colorado Department of Natural Resources regulates cloud seeding, permitting operations in nine different parts of the state. The operations in the central zone, at the headwaters of the Colorado River, are funded by a wide range of groups, including Front Range utilities and water districts that divert Western Slope water, including Denver Water and Northern Water.

The Colorado River District spends around a $150,000 a year contracting with Western Weather Group to run the program, which Kanzer said is about the same amount Vail Resorts spends on the program for its four Colorado ski areas – Vail, Beaver Creek, Breckenridge and Keystone.

Vail Resorts declined to comment for this story.

Kanzer presented on cloud seeding at a November Eagle River Watershed Council meeting in Avon, where a few of the 50 or so participants got heated in their questioning of the environmental safety of the process.

Kanzer said cloud seeding is safe, using inert silver iodide that cannot be detected in the environment after it’s released into clouds. He added the process could become increasingly critical to maintaining mountain snowpack as the climate changes.

“It’s one tool that we can use to mitigate or adapt to the changes that we have not only predicted but are starting to experience with shorter snow-covered seasons,” Kanzer said. “And so [cloud seeding] helps us extend that time or at least forestall the reduction.”

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David O. Williams

Managing Editor at RealVail
David O. Williams is an award-winning freelance reporter based in the Vail Valley of Colorado, writing on health care, immigration, politics, the environment, energy, public lands, outdoor recreation and sports. His work has appeared in 5280 Magazine, American Way Magazine (American Airlines), the Anchorage Daily News (Alaska), Aspen Daily News, Aspen Journalism, the Aspen Times, Beaver Creek Magazine, the Chicago Tribune, the Colorado Independent (formerly Colorado Confidential), Colorado Politics (formerly the Colorado Statesman), Colorado Public News, the Colorado Springs Gazette, the Colorado Springs Independent, the Colorado Statesman (now Colorado Politics), the Colorado Times Recorder, the Daily Trail (Vail), the Denver Daily News, the Denver Post, the Durango Herald, the Eagle Valley Enterprise, the Eastside Journal (Bellevue, Washington), ESPN.com, the Glenwood Springs Post-Independent, the Greeley Tribune, the Huffington Post, the King County Journal (Seattle, Washington), KUNC.org (northern Colorado), LA Weekly, the London Daily Mirror, the Montgomery Journal (Maryland), The New York Times, the Parent’s Handbook, Peaks Magazine (now Epic Life), People Magazine, Powder Magazine, the Pueblo Chieftain, PT Magazine, Rocky Mountain Golf Magazine, the Rocky Mountain News, Atlantic Media's RouteFifty.com (formerly Government Executive State and Local), SKI Magazine, Ski Area Management, SKIING Magazine, the Summit Daily News, United Hemispheres (United Airlines), Vail/Beaver Creek Magazine, Vail en Español, Vail Valley Magazine, the Vail Daily, the Vail Trail and Westword (Denver). Williams is also the founder, publisher and editor of RealVail.com and RockyMountainPost.com.

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