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Tue, January 31st, 2017 - 7:00AM
Wed, February 1st, 2017 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is MODERATE  at all elevations in Turnagain Pass but could rise to CONSIDERABLE in the alpine  by the afternoon. Human triggered wind slabs 6 €-15 € thick are possible on slopes steeper than 35 degrees and slab size will depend on how much snowfall we receive today. There is also the possibility for triggering a large (2-3′) slab avalanche that breaks lower in the snowpack. The most suspect areas are on the South end of Turnagain Pass where the snowpack is shallower and there has been little traffic this season.  Last, cornice falls are still a concern along ridgelines and small wet loose avalanche are possible below 1000′ should snow turn to rain.

Girdwood Valley:   A shallower snowpack exists in the Girdwood Valley and slab avalanches have the potential to be larger, over 3′ thick, and break near the ground.  Expect wind loading and snowfall today to add stress to an already stressed out snowpack.

Summit Lake:   Dangerous human triggered slab avalanche conditions persist in the Summit Lake zone. Check out the Saturday Summit Summary  HERE.  

**The probability of triggering one of these large slabs is decreasing but the consequences remain high. This is more reason to be sure to carry your rescue gear and practice safe travel protocol – such as exposing one person at a time, grouping up in safe zones, having escape routes planned and watching your partners!  

Special Announcements

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

  • A preliminary report is out with a few photos regarding the snowmachine avalanche fatality in the Snug Harbor area on Saturday. The final report with finalized details on the events, rescue and snowpack analysis will be posted in the next couple days. Our thoughts continue to be with the victim’s family, friends and rescuers.
  • The  Southern Kenai Mountains, including Snug Harbor and Lost Lake zones continue to have dangerous avalanche conditions. This region is out of the advisory area but large human triggered slab avalanches 3-5 thick are possible on slopes over 35 degrees.  Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.
  • Click  HERE  for the Hatcher Pass Avalanche Center advisory and  HERE  for recent snowpack observations.
Tue, January 31st, 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
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

Wind Slabs: Yesterday afternoon ridgetop winds bumped up into the 30’s mph from the East and wind loading was observed in the alpine. Today an additional 3-8” of snow is expected and ridgetop winds will be in the 15-30mph range. Expect wind slabs to be tender, 6”-15” thick on leeward terrain features.  These fresh slabs are expected to be sensitive to human triggers on slopes steeper than 35 degrees. Visibility may be limited today, but watch for blowing snow, stiffer snow over softer snow, or cracks that shoot out from your snowmachine or skis. Slope testing small (low consequence) slopes and performing quick hand pits are all good ways to assess whether you have found a wind slab. Should snowfall become heavy today or more snow falls than forecasted, these slabs could increase in size and become more consequential. Be prepared to change your plans should conditions worsen. 

Wet Snow: There is some uncertainty today in how warm temperatures will rise and how much precipitation will fall. Should snowfall transition to rain, small wet loose avalanches are possible in the lower elevations below 1000’. These are not likely to bury a person, but could catch you by surprise especially in areas with terrain traps. This will be an important thing to keep in mind if headed to the Placer Valley today.

Cornices have been growing in size over the last few weeks and with additional loading today could be extra tender. Give these unpredictable features extra space along ridges and avoid being under these features, as they could release naturally and without warning.

Cross loaded gullies with pillowed snow along ridges – an example of terrain features that may harbor tender wind slabs today. Photo taken 1/30/17 of an East facing slope on the South end of Seattle Ridge near Bertha Creek Camp Ground. 


Avalanche Problem 2
  • 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

The January 26th storm event added 2-3′ of snow to the upper elevations and overloaded a variety of weak layers causing a widespread avalanche cycle in the region. The good news is the snowpack in the heart of Turnagain Pass is showing signs of adjusting to the load, the bad news is other areas are not. This can make for difficult snowpack assessment as the weak layers of concern (depth hoar, facets and buried surface hoar) are lurking anywhere from 2-4+ feet below the surface. Thicker snowpacks, as found at Turnagain Pass, had a stronger snowpack to begin with and has allowed for a quicker adjustment. This is opposed to the persisting unstable snowpack found South of Turnagain Pass and the Girdwood Valley.

In Turnagain Pass – this is a high consequence but low probability situation and may require a big trigger like multiple people on a slope or finding just right trigger spot in a thinner area of the snowpack. In Girdwood, Johnson Pass, and Summit Lake today’s storm will be adding stress to an already stressed snowpack and tipping the balance may be easier in these locations. Should you experience collapsing “whumpfing” sounds, or see any avalanche activity, these are obvious clues the snowpack is unstable. 

If choosing to ride or ski the steeper terrain, we recommend using safe travel protocol, only exposing one person at a time and grouping up in safe zones. If a large slab is triggered it may run further than expected and wrap around terrain features taking out mid-slope relative safe zones.

A Northern aspect of Pete’s South where a generally thinner snowpack exists and where there’s more potential to trigger an avalanche in an older deeper layer of the snowpack. Photo taken yesterday 1/30/17.

Tue, January 31st, 2017

Yesterday temperatures were on the rise throughout the day approaching the low 30F’s near sea level by late afternoon. Skies were cloudy becoming overcast by mid day. Moderate Easterly ridge top winds, 15-30mph, bumped up into the mid 20’s mph by late afternoon with gusts in the 40’s. Only an inch of new snow was recorded overnight.  

Today a frontal system has pushed into the Gulf of Alaska and warm temperatures and snowfall are expected. There is some uncertainty as to how much will precipitation will fall, with a range from 3-8 €, but more or less is possible. Easterly ridge top winds are expected to be moderate,15-30mph. Above freezing temperatures are expected below 1000′, and rain may fall into this elevation band today. Tonight there is a chance for an addition 2-6 € of snow.

Tomorrow temperatures are expected to cool and snow showers are possible. Winds are expected to decrease this evening and clear skies are in the forecast later in the week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29   1   .1   58  
Summit Lake (1400′) 25   1   .1   25  
Alyeska Mid (1700′)  27 trace   .06   51  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19   ENE   19   49  
Seattle Ridge (2400′) 20   SE   21   49  
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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.