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Sat, January 16th, 2016 - 7:00AM
Sun, January 17th, 2016 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

There is a MODERATE avalanche danger in the Turnagain Pass region for both glide avalanches as well as fresh wind slab avalanches. At the mid-elevations (between 1,000′ and 2,500′) destructive glide avalanches are possible. Several of these have released over the past 3 days and could release again today. In the upper Alpine zones, ridgetop winds are expected to be strong enough to form shallow wind slabs on leeward slopes. If this is the case, human triggered wind slabs will be possible.

Note: Glide avalanches are a different ‘avalanche beast’, they are not something a person can trigger – they release spontaneously on their own. This is why we keep preaching avoidance and limiting exposure under glide cracks, it’s a wrong place at the wrong time scenario. More on this below.

There are many safe areas to recreate today. These are areas that DO NOT have glide cracks above and slopes that are not being loaded by today’s winds.

Sat, January 16th, 2016
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Avalanche Problem 1
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide avalanches are stealing the show this week. There have been at least 4 glide cracks that have avalanched in the past 2-3 days (Seattle Ridge East face, Eddies South face, Wolverine South face, Skookum North face). These have been roughly between 1,500′ and 2,500′ in elevation and on all aspects. If you do the math, the percentage is quite low a crack will avalanche – I counted over 100 glide cracks yesterday from one spot on Turnagain Pass. So 4 out of 100, that’s a 4% chance, or less, a crack will release? You can’t really do it this way, but the point is, there are numerous glide cracks out there and not all of them will avalanche – but it’s just not worth it, these are killers if you are in the wrong place at the wrong time.

What can we do about them? Glide avalanches are like crossing a road, you can look both ways or not, it’s your choice to expose yourself when cars are coming, or not. They are easily avoided by taking stock of your surroundings. If you can’t see what is above you (or below you) then go to a different slope; avoidance and limiting exposure under cracks is the key. The South face of Tincan and the East face of Seattle Ridge are probably the two areas where folks are traveling under glide cracks the most (photos below). 

Photo below: Glide avalanche on the Easterly face of Seattle Ridge that ran sometime in the last 2 days. You can see two large cracks on either side of the avalanche. More photos HERE.

Photo of the South face of Eddies. This avalanche was not only heard, but seen in action, by the party sending in this photo. See that report HERE.

Photos below show evidence of recent glide activity in Skookum Valley near Portage. These glides are ~1,500′ and North aspect. (Credit: Predeger and Thamm)

Tracks under several glide cracks on the South side of Tincan, under Common Bowl.


Photo below: 8-10′ deep glide crack on Tincan under the CFR ridgeline. This is the large crack lower in the trees facing the road. Credit: David Pettry.

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

After several days of calm conditions, the Easterly winds bumped up yesterday afternoon on the ridgetops. We had one report from Sunburst (near the weather station) that these winds were transporting snow. For today, we should see winds bump back up to the 10-20mph range from the East. There is enough snow available for transport that if the winds do increase, we could see shallow slabs form in the higher elevations (6-10+” thick). 

Watching for active wind loading and areas with wind drifted snow will be key. Also, feeling for stiffer snow over softer snow with your pole or boot can help suss out if winds have created slabs. 

Sat, January 16th, 2016

Partly sunny skies yesterday gave way to cloud cover late in the afternoon. The Easterly ridgetop winds also moved in late in the day. Temperatures were chilly (teens) in the parking lots and 20’s F on the ridgetops.  

Today looks to be mostly to partly cloudy. We are seeing another band of cloud cover being pushed our way by a  large low-pressure system spinning South of the Aleutians. The ridgetop winds remain light from the East this morning but are expected to pick up to 10-20mph by the afternoon. Temperatures are in the mid 20’s F at 1,000′ and the low 20’s on the ridgelines where they should remain today.

For tonight into Sunday, we could see some light snow showers above 1,000′ and rain at sea level. Stay tuned.

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28    0 0   81  
Summit Lake (1400′) 25    0 0   24  
Alyeska Mid (1700′) 29     0   0   62  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE   10   35  
Seattle Ridge (2400′) 25   N/A    N/A N/A  
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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.