Avalanche Advisory

Turnagain Area Avalanche Advisory Wednesday, February 12th 2014 6:25 am by Wendy Wagner ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.

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We continue to have a MODERATE avalanche danger on all aspects above treeline. Human triggered soft slab avalanches remain possible on slopes where a slab 12-20” thick sits on a thin layer of weak faceted snow. Most suspect areas are those that have seen prior wind loading. In locations where the slab has weakened and is comprised of very loose snow, sluffing should be expected in steeper terrain.

Below 2,000 feet the avalanche danger is LOW and triggering an avalanche will be unlikely where 3-15 inches of loose snow is resting on either a frozen ground or a stout crust.

Show the Complete North American Avalanche Danger Scale

North American Public Avalanche Danger Scale Avalanche danger is determined by the likelihood, size and distribution of avalanches. Danger Level Travel Advice Likelihood of Avalanches Avalanche Size and Distribution 5 Extreme Avoid all avalanche terrain. Natural and human- triggered avalanches certain. Large to very large avalanches in many areas. 4 High Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Natural avalanches likely; human- triggered avalanches very likely. Large avalanches in many areas; or very large avalanches in specific areas. 3 Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human- triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. 2 Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human- triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. 1 Low Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human- triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain. Safe backcountry travel requires training and experience. You control your own risk by choosing where, when and how you travel.

2 Moderate Alpine / Above 2,500'

Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1 Low Treeline / 1,000'-2,500'

Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1 Low Below Treeline / Below 1,000'

Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1

It was a quiet day in the backcountry yesterday (avalanche-wise) though many folks were out continuing to enjoy the sunny weather and Friday’s unexpected 14-18” refresher. The last avalanche reported on the Pass was Monday, two days ago, where a snowboarder triggered a soft slab in Seattle Creek. Otherwise, there have been a few reports of remote triggered shallow slabs Sunday and Monday north of the Pass (20mile area) as well as south (Grandview region).

The main concern for today continues to be triggering one of these persistent soft slab avalanches. These slabs have been in the 12-20" range and are sitting on a thin layer of faceted snow over a crust. It is interesting how spatially variable both the slabs are as well as the thin layer of faceted snow underneath. Many areas simply have no slab at all, only loose unconsolidated snow. Yet in other areas, people are still finding snow with just enough slab character to trigger an avalanche. If you didn't read it yesterday, check out this great article on spatial variability by Ron Simenhois (inventor of the very popular ECT test). This is one of those set-ups that can lull us into complacency. Just because the ridge next to you was tracked-out without incident doesn't necessarily mean yours is good to go. Every slope should be evaluated on its own, especially if you are venturing into steeper and more complex terrain where triggering even a small slab could have higher consequences. Watching for cracking or collapsing as well as performing hand pits, proper ski cuts and having an escape route planned are ways to manage this issue.

Avalanche Problem 2

Loose snow avalanches, or sluffs, are becoming easier to initiate as the top foot+ of snow continues to become looser by the day. The past four days of clear and cold conditions are eating away (or faceting) Friday and Monday's snow. Sluffs yesterday were mainly low volume, predictable and confined to slopes around 40 degrees and steeper. With continued cold temperatures, watch for these to start entraining more snow and run further.

The deep slab issue is still of concern in the upper most elevations of our forecasting zone. The likelihood of triggering a full depth avalanche breaking in weak snow near the base of the pack is low but the consequences remain high.

This problem is not a concern below 3000ft where the previously water saturated layers have now frozen into a very strong and stable layer.

Sunshine, light variable winds and single-digit temperatures prevailed again yesterday. Overnight, skies have remained mostly clear and the temperatures have plummeted - minus single digits are being seen at all elevations: -5 to -10F at sea level and -2F on the ridgetops. Winds are still light from a Northerly direction around 3-5mph.

For today, mostly clear skies will be replaced with clouds and a chance for a falling snow crystal or two. Temperatures will continue to be cold and may even reach the minus double digits in valley bottoms - burrr. The good news for anyone venturing out today is the wind will be light from the North, ~5mph or less. This may not help to warm things up however if the clouds keep the sun at bay.

For tonight and into tomorrow there is a chance for snowfall as a large area of low pressure develops in the Northern Gulf spreading small amounts of moisture our way. However, the temperatures remain below 0F which is not an ideal set up for snow accumulation. But, we can hope for the best, which would be around 4-5" by Thursday night.

Check out this graphic by the NRCS. It shows general snowpack depth for the state as of February 1st. Yes, too much red... 

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Apr 20, 2018 )

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