Avy Report: The difference between low and no

The Crested Butte Avalanche Center report from March 4.

The Crested Butte Avalanche Center report from March 4.

High pressure systems are making themselves at home in the Rocky Mountain region, greatly reducing the avalanche danger forecast ratings from Utah all the way up to Montana. This trend in increased stability sits in stark contrast when compared to that of January and early February when slab avalanches and depth hoar were prevalent dangers.

The Utah Avalanche Center (UAC) reminds us, however, that “low doesn’t mean no.” This caution is mainly a result of potential wind loading that could result in localized windslab and cornices. Another danger is the chance of wet slides on south-facing aspects and in areas experiencing warming trends that are sweeping across the west.

“The only item of interest from yesterday’s observations were reports of small pockets of fresh wind drifts at upper elevation ridgelines in the Salt Lake mountains,” the UAC reported on March 3. “These were shallow (one to eight in. thick) and isolated.”

In Colorado, the Crested Butte Avalanche Center (CBAC) has seen similar warming trends to Utah, but the CBAC warns backcountry travelers to remain cautious of instabilities in the snowpack on colder aspects.

“Our only recent avalanche activity in the past few weeks, aside from small facet sluffs, has been a couple of natural cornice fall/ persistent slab events on northeast aspects above treeline,” explains the CBAC. “Human triggering a large, persistent slab has become very unlikely during the past month of mild and dry weather, but you can further reduce your risk to this problem by steering away from the steep, shaded, high elevation slopes harboring variable snow depths and numerous shallow points.”

Some zones under the purview of the Gallatin National Forest Avalanche Center in Montana remain labeled under a low avalanche danger caution, but pockets of moderate exist where new snow has fallen.

“Wind slabs and buried surface hoar make avalanches possible to trigger today,” say the Gallatin National Forest Avalanche Center for March 3.

One area in the west that is seeing increased avalanche danger is Washington State, where a number of warmer days allowed a melt-freeze crust to form. Recently a storm moved through the region, depositing a number of inches of new snow. This created a dangerous storm slab in all regions observed by the Northwest Avalanche Center (NWAC) and elevated the danger rating to considerable on most aspects and elevations.

“Storm slab instabilities should be stabilizing, but may still be sensitive Thursday,” reports the NWAC. “Wind slabs will continue to build Wednesday night on lee slopes, facing generally NW-NE. Earlier formed wind slabs may still be reactive Thursday and may add to the increasingly complex snow structure, by Thursday.”

Bottom line: Spring can bring a false sense of security when it comes to avalanche danger. Always make sure to check in at your local avalanche forecasting center to find the most recent avalanche observations. The “low” rating you saw last week may now be a “moderate” or “considerable” rating due to factors you might not be aware of. Stay informed and remember, “low doesn’t mean no.”

For a full report on U.S. avalanches, visit the Colorado Avalanche Information Center website and your regional avalanche forecasting service.

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