Turnagain Pass RSS

ARCHIVED - Forecasts expire after 24 hours.
Sat, February 11th, 2017 - 7:00AM
Sun, February 12th, 2017 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

There is a MODERATE avalanche danger in the Turnagain Pass area. Triggering a fresh wind slab in leeward terrain is possible. In protected areas triggering a shallow storm slab or loose snow avalanche is also a concern. In addition, keep in mind that  due to poor snowpack structure there is still a chance of  triggering a large slab avalanche (2′-5′ thick) that breaks near the ground.  

Summit Lake: Make sure and check the Saturday Summit Summary  HERE.

Special Announcements

As you make plans this weekend remember that many areas around Southcentral, Alaska including the  Southern Kenai Mountains, Seward, Snug Harbor and Lost Lake,  Anchorage Front Range,  Hatcher Pass  have had an unstable snowpack over the past few weeks.  Human triggered large avalanches, breaking near the ground, are still possible.  Please see links above for recent activity.  Careful snowpack evaluation and cautious route-finding are recommended.  

TODAY:  CNFAIC and the Anchorage Snowmobile Club will be hosting a FREE Avalanche Rescue Workshop  at Turnagain Pass, 11am -12:30pm in the Motorized parking lot.  We will focus on practicing with your beacon, probe and shovel. This workshop is open to everyone and anyone, PLEASE JOIN US!! Click  HERE  for more details.  


Sat, February 11th, 2017
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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
  • 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

The snow that fell yesterday was light and fluffy and the kind that will easily blow around and form tender wind slabs. Overall the winds weren’t strong but there was period of more sustained wind last night. The new snow fell on surface hoar, near surface facets and sun crusts and was not bonding well. This should make winds slabs easy to trigger but due to limited snow totals the slabs shouldn’t be that deep (6″-1′). Look for pillowed or drifted areas in leeward terrain and pay attention to shooting cracks. 

In areas not affected by wind there is also potential for shallow storm slabs and loose snow avalanches due to the new snow not bonding well to old snow surfaces. When the sun comes out today look for point releases on steep solar aspects. 

Storm snow easliy failing on buried surface hoar in a shovel tilt test yesterday.

Buried surface hoar over a micro sun crust @ 2200′ on Sunburst yesterday.


Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

Weak snow (facets and depth hoar) in the lower layers of the snowpack lingers as an issue in our advisory area. It has been 8 days since the last human triggered avalanches on these layers. However, triggering a deep slab is still a possibility if you find the wrong spot and a concern due to the depth of slab overlying the weak snow. The likelihood for someone to find and trigger a large slab is decreasing as the snowpack adjusts, but the poor snowpack structure remains and the consequences are scary. Both near miss avalanche accidents last week were triggered in thinner areas of the snowpack, on slopes that already had tracks on them. The tricky part about this particular avalanche problem is that it is very difficult to assess. Obvious signs like whumpfing and shooting cracks are unlikely and stability tests may not be reactive. Just because a slope has tracks on it does not mean it is safe. Likely places to trigger a deep persistent slab will be near rocks or in thin zones where affecting the weak layer is more of a possibility. Likely triggers are large: snowmachines, groups of people or cornice falls. Identify and avoid terrain traps (like large gullies).

Snow pit @ 2200′ on Sunburst yesterday. Note the soft (weak, faceted snow) under the hard slab. 

Additional Concern
  • Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Last weekend cornice cracks were reported along the back bowls of Seattle Ridge. A few chunks have been triggered this week. Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

Sat, February 11th, 2017

Yesterday skies were obscured and light, low density snow fell throughout the day.  Temperatures were around 0 in the Alpine and teens/single digits in valley bottoms. Winds were mostly light and shifted from the West to the North. There was an uptick in winds that saw gusts up to 40 mph in the early evening. Light snow showers continued overnight.  

The chance for snow showers decreases this morning with clearing skies. Today temperatures will remain cold 3-13F and winds will be light and Northerly.  Tomorrow the pattern shifts as warm, moist air moves in with the first of a series of low pressure systems on track to affect the area. Stay tuned for details!  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 5   6    .3 58  
Summit Lake (1400′) 0    1  .1  25
Alyeska Mid (1700′)  6 6.5    .2  53

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 2    WNW-ENE 10 42  
Seattle Ridge (2400′)  -1 NNE    5 21  
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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.