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Sat, January 28th, 2017 - 7:00AM
Sun, January 29th, 2017 - 7:00AM
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger is  CONSIDERABLE  on upper elevation slopes where triggering an avalanche on a persistent weak layer or a  wind slab 2-3′ thick is likely and cornices are suspected to have grown large and be tender.  Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential today.  At Treeline and below  the danger will be  MODERATE  where triggering an avalanche on a persistent weak layer will still be possible.  Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!!  

Girdwood Valley:  Slabs have the potential to be larger due to more snow that has fallen on a weaker snowpack compared to Turnagain Pass. Avalanches were running to the ground during the storm.  

Summit Lake: Dangerous avalanche conditions exist.  Please check out the Saturday Summit Summary  HERE.  

Special Announcements

Dangerous avalanche conditions exist in many area around Southcentral Alaska including the Anchorage Front Range, Hatcher Pass, and Southern Kenai Mountains  

  • Click  HERE  for the Hatcher Pass Avalanche Center advisory and  HERE  for recent snowpack observations.
  • The Southern Kenai Mountains, including the Lost Lake zone are expected to have dangerous avalanche conditions today. This region is out of the advisory area but received 3-5 feet of snow from last Saturday’s storm and received additional snow this week. There were several avalanches observed over the past weekend in that zone and more are possible today.  Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!!
Sat, January 28th, 2017
Above 2,500'
3 - Considerable
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
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

As we got a few patches of visibility over the past two days we have been able to see evidence of the natural avalanche cycle that occurred during the storm and were reminded of the variability of the snowpack across the advisory area. In Girdwood Valley some avalanches were running to the ground on basal facets that formed early in the season. A similar weak layer is also the suspected culprit in a number of large avalanches that ran in the gullys at the southern end of Seattle Ridge.  At lower elevations in Turnagain Pass there were signs that avalanches were running on the January 13th layer of buried surface hoar. All these persistent weak layers still need time to adjust to the heavy load they received and could be triggered today. Shallow areas in the snowpack will be the most likely trigger spots. Be on the lookout for cracking and collapsing and areas where you can feel weak snow below strong snow. Do not overload steep slopes with multiple skiers or snowmachines on the slope at the same time! 

Yesterday at lower elevations it was easy to find the rain/snow line around 1400′. Water had formed two layers below the surface that were slowly cooling and may have formed crusts overnight. If these are solid today the likelyhood of triggering the January 13th buried surface hoar will go down. If the upper snowpack is still wet, persistent slabs may still be possible. 

Seattle Ridge South, both the gully and the face slid. Road obs yesterday showed that most of the gullys in this area slid and some made it all the way to the creek. 


Slab in above Tincan Gorge. Supected weak layer Janurary 13th buried surface hoar. Photo: Joe Kurtak

Snowpit on Tincan at 1100′, shows the layers of wet snow and the January 13th buried surface hoar


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

Strong easterly winds during the storm quickly moved snow, loaded slopes and triggered natural avalanches. Probing around a minor ridge yesterday showed that the winds had definitely redistributed snow. The windward side had less than a meter of snow and leeward side had over 2 meters. There was wind features in all of the Alpine terrain that was visible. Today wind slabs 2-3′ thick are likely on steep leeward slopes. It will be important to look for pillowed or drifted areas and watch for shooting cracks. These slabs may allow you get out onto them before they break. There is still snow available for transport today and the winds are shifting to the west. Pay attention to changing conditions if you see blowing snow and slopes being actively loaded.

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

Warm wet snow and strong winds are notorious for cornice growing. We have had limited visibility into the Alpine but suspect they will be looming over much of the leeward terrain. Give cornices wide berth, avoid travel on slopes below and remember they can break farther back onto the ridge than expected.  If they do break and fall they could trigger an avalanche on the slope below.

Sat, January 28th, 2017

Yesterday was mostly cloudy with snow showers throughout the day. Easterly winds were light with a slight uptick in the evening with gusts in the 20s. Temperatures were in the 30s at valley bottoms and 20s at ridge tops. There was a slight cooling trend overnight.  

Today will remain cloudy with snow showers forecasted throughout the day. Accumulations will be minimal. Temperatures will be slightly cooler than yesterday. Winds will be westerly 10-20 with gusts into the 30s. Snow showers diminish overnight but cloudy skies and a chance of snow remains through the weekend.    

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  32 1    .1  61
Summit Lake (1400′)  30  1  .1  27
Alyeska Mid (1700′)  30  2  .2 57  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  21 ENE   10   31  
Seattle Ridge (2400′)  24  rimed rimed   rimed  
Recent Observations for Turnagain Pass
Date Region Location
11/27/23 Turnagain Avalanche: Tincan Ridge
11/26/23 Turnagain Observation: Road report: Slide with dirt on Repeat offender
11/26/23 Turnagain Observation: Pete’s North
11/25/23 Turnagain Observation: Tincan trees
11/21/23 Observation: Spokane Creek
11/20/23 Turnagain Observation: Sunburst
11/19/23 Turnagain Observation: Magnum – PMS Bowl
11/19/23 Other Regions Observation: Sunnyside/Penguin
11/19/23 Turnagain Observation: Eddies
11/19/23 Turnagain Observation: Cornbiscuit
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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.