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Thu, February 8th, 2018 - 7:00AM
Fri, February 9th, 2018 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is  MODERATE  above 2,500′ for triggering a slab 1-2′ deep. Watch for cornices along ridgelines and €˜sluffs’ in steep terrain. LOW danger below 2500′ doesn’t mean No danger. Evaluate the terrain for consequences before committing to a slope.

*For the periphery zones, such as Girdwood to Portage Valley, and Johnson Pass to Summit Lake, more caution is advised where a slab could be larger and more connected.

Check out the Summit Lake Summary  HERE.

Special Announcements

For all the Hatcher Pass users out there – Hatcher Pass Avalanche Center is having their annual fundraiser this Saturday night, Feb.10th, at the Palmer Moose Lodge!! HPAC is a growing avalanche center for a high use zone with a high number of avalanche accidents in Alaska, they need your support! Click  HERE  for details.

Thu, February 8th, 2018
Above 2,500'
2 - Moderate
Avalanche risk
1 - Low
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
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Several inches of new snow fell inTurnagain Pass on Tuesday combined with elevated ridge top winds. Yesterday several small natural slabs were noted in the Seattle Creek zone and activity near Byron Glacier was also reported. Several weak layers are buried within the top 1-2’ of the snowpack, most notably the 1/21 buried surface hoar which has been responsible for the scattered avalanche activity over the last two weeks. In Portage, where 8-10” of snow fell on Tuesday, recently buried surface hoar could be an additional new layer of concern in this area.    

Over the last week in Turnagain Pass, slabs have been relatively small and hard to find, considering the high volume of snowmachine and skier/rider traffic this area has seen. Don’t let old tracks fool you into thinking all these slopes are safe. If you see evidence of wind-pillowed snow or stiff snow over weak snow, be cautious in steep terrain. Snow that was once loose may have become more cohesive and ‘slab-like’ in the alpine on specific terrain features. Before committing to steep terrain, identify terrain traps like gullies, cliffs or rocks below and consider the consequences if even a small slab is released.   

*Deep Persistent Slab:  Weak snow can still be found near the ground at the upper most elevations in our forecast area, 3,000′ – 5,000′. Although triggering a Deep Persistent Slab is very unlikely, it is worth keeping in mind that poor structure does exist at the high elevations.

A thinner and weaker snowpack is more suspect in Summit Lake and the far Southern end of Turnagain Pass, where a skier triggered avalanche occurred on Saturday (Feb.3) on the East face of Twin Peaks, along the edge of our forecast zone. This avalanche stepped down into older layers of the snowpack. The party’s account can be found HERE and stay tuned for a near miss report coming soon. 



Wind affected snow was more obvious on the Northern end of Turnagain Pass yesterday. Photo of Western Bowl of Wolverine.


In addition to the 1/21 buried surface hoar we are also tracking a facet/crust combo between 2500’ and 3500’ that has shown propagation potential recently. 


Additional Concern
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Loose snow avalanches (’sluffs’): In Turnagain Pass a few inches of loose dry snow fell Tuesday and numerous small point releases were observed yesterday. In places protected from recent winds, expect this loose snow to be small in volume, but could slide easily in steeper terrain with the weight of a person. Watch your ‘sluff’ and be aware of the consequences below you.

Cornices: Cornices are unpredictable and can break further back along a ridge than expected. Give these features plenty of space.


Very shallow sluffs in steep terrain from the new snow on Feb 6. Photo taken in Seattle Creek yesterday. 

Thu, February 8th, 2018

Yesterday skis were partly cloudy with some patches of valley fog. Ridge top winds were light and variable. Temps at all elevations dipped into the teens (F) with pockets of cooler air, single digits, in  some valley bottoms. In   coastal areas temps remained in low 20F’s. No precipitation was recorded.  

Today expect clear skies and temperatures to increase into the mid 20F’s. Ridgetop winds will be light from the Southeast and no precipitation is expected.  

Friday should be partly cloudy with increasing cloud cover in the evening. Temperatures may increase into the upper 20F’s. There is a chance for snow showers over the weekend and a possibility ridgetop winds may increase to moderate on Saturday, but there remains much uncertainty in the details of the extended forecast at this point.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 20   0   0   63  
Summit Lake (1400′) 12   0   0   20  
Alyeska Mid (1700′) 19   0   0   52  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 15   WNW   4   16  
Seattle Ridge (2400′)  15 ENE   4   12  
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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.