Wind, snow create deceiving snowpack in Summit County
Ryan Summerlin February 28, 2012
Snow and wind combined Tuesday to boost snowpack on the slopes but also elevated avalanche danger in the backcountry.
Colorado Avalanche Information Center forecaster Brian Lazar anticipated avalanche danger rising to considerable on below-treeline, wind-loaded slopes by Tuesday afternoon.
“With the high wind speeds and swirling gusts, you will find snow drifting lower than usual on slopes, cross-loading around terrain features, and in open areas below treeline,” Lazar said.
As wind slabs stack on strengthening midlayers in the snowpack, it can give a false sense of stability when they’re still perched on a weak, faceted snow foundation. A slide triggered in a wind slab layer could step down to deeper layers, Lazar said. Loading shallow spots could also trigger a slide in a persistent slab.
“You need to be careful in your route and terrain selection today,” Lazar said.
Strong winds in recent days have scoured some slopes and loaded others in “unusual ways,” Lazar said. “You can expect loading well down off ridgelines and lower in the start zones. Wind loaded pockets exist on northwest though east to south aspects at all elevations and in gullies, below sub-ridges, and in open areas well below treeline. The primary avalanche concern today is triggering a freshly-formed wind slab.”
Resorts didn’t report significant snowfall in their Tuesday morning readings, but Copper Mountain’s snow stake camera showed that nearly 9 inches of snow had fallen between 4:30 a.m. and 4:30 p.m.
The storm is expected to drop up to 15 inches of snow through Tuesday night, depending on the location. Areas west of Vail Pass are expected to get the majority of the snow. Snowfall intensity was expected to drop off Tuesday afternoon, with moderate accumulation through the night.
Another system is expected on Thursday through Friday morning with a brief break in the clouds with Wednesday’s weak high pressure ridge.