Photo by Tom Ross
The combination of cold clear nights and open water on the Yampa River has coated cottonwood trees near Rotary Park with frost.
Thursday, November 26, 2009
Steamboat Springs The snowstorm that blustered through Steamboat Springs on Monday boosted the snowpack above 10,000 feet on Buffalo Pass by 11 inches to a total of 41 inches early Tuesday morning.
The snow had settled to a depth of 37 inches by late Wednesday morning, according to a Web site maintained by the University of Utah that tracks weather stations all across the country, including the Tower snow measuring site on Buffalo Pass.
“Snow is always settling, and settlement in the new snow at Tower is about normal at the current rate,” said Art Judson, Steamboat weather observer and retired avalanche forecaster.
The arrival of fresh snow after nearly a week of cold nights without precipitation did not raise alarm bells at the Colorado Avalanche Information Center on Tuesday where the staff reported that it had insufficient information to rate the potential risk of a snow slide.
“Our current storm didn’t produce enough snow to bring the hills down, but a little snow and a little wind on a weak snowpack will create some tender slabs today,” forecaster Ethan Greene wrote on the information center’s Web page. “The biggest precipitation numbers came from the Tower and Columbine (east side of Rabbit Ears Pass) SNOTEL sites. If you’re traveling in areas with about 1 foot of new snow, you might be able to trigger a new snow, soft slab avalanche on slopes steeper than about 37 degrees.”
The avalanche report had not changed as of midday Wednesday.
Daily density increases
Judson explained how the density of the snowpack increases in the hours after a fresh snowfall. Density is an expression of how much water is contained in standing snow of a certain depth.
“To get the density, you divide the snow depth into the water equivalent,” he said.
Snow measuring sites maintained by the National Resources Conservation Service remotely sense the weight of the snowpack (revealing the water content) and its depth.
Snow depth had settled on Buffalo Pass on Wednesday to a depth of 37 inches and contained 9.5 inches of water. Simple division indicates a density of 0.256.
“In Steamboat, the average density of new snow is 0.07. (actually 0.072),” Judson said. “One inch of snow with 0.07 water-equivalent equals a density of 0.07. To get the density, you divide the snow depth into the water equivalent. The main thing to remember is that snow is always densifying until it reaches the density of ice, which is 0.917.”
In the case of the new snow near the summit of Buffalo Pass this week, the depth increased from 29 to 41 inches with the storm, Judson said. Typically, it could be expected to settle back to about 35 inches the fourth day after the storm.