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Fri, January 9th, 2015 - 7:00AM
Sat, January 10th, 2015 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

Today the avalanche danger is MODERATE at both Treeline and in the Alpine. Small human triggered wet avalanches are possible on very steep slopes and wind slabs 1-2′ deep could be found at elevations above 3500′. Avoid steep slope angles and in general be careful €“ the snow conditions are relatively poor and also ripe for non-avalanche related injuries.  

Special Announcements

Do you ski or snowmachine in Hatcher Pass?   The Hatcher Pass Avalanche Center (HPAC) and the Alaska Avalanche School (AAS) are leading an Observer’s Workshop for backcountry enthusiasts who are interested in submitting snow and avalanche observations to the HPAC.    More info can be found by clicking here.

Fri, January 9th, 2015
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

In the last 24hours a low-pressure system has brought us very warm temperatures (40’sF) at sea level and rain to 3000’. In Turnagain Pass .5” of water was recorded and double that amount in Girdwood.

No avalanche activity was reported or observed yesterday, but today small wet loose avalanches are the primary concern in areas where low-density snow is poorly bonded. Rain saturating the snowpack can cause this type of snow to weaken and fail, more easily than in denser snow.

It is important to understand that our current snowpack is comprised of large areas of dense supportable snow in the Alpine, but pockets of weaker snow do exist. Triggering a wet loose avalanche requires a steep slope (>40°) and could be larger on sustained slopes. Today this problem will be more likely at mid elevations where there are greater areas of low-density snow.

Expected this type of avalanche to be slow to initiate, meaning they take a little time to gain momentum. Use caution if you choose to ski/ride in steep terrain today.  This kind of avalanche problem is wet and heavy and can easily grab your ski/board and pull you down.

Today light precipitation (0.1”) is expected throughout the day and rainline may decrease to 1000’. This is not enough precipitation to increase the likelihood of natural avalanches. 

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

At higher elevations, above 3500’, where snow has accumulated there is potential for wind slabs. Yesterday ridgetop winds were from the East and averaged 30mph. Avoid wind loaded leeward slopes if you venture above 3500’. Small pockets 1-2’ deep could be found on leeward sides of ridges and along terrain features such as gullies.

Luckily today with marginal weather and poor surface conditions this terrain will not be very attractive to ski/ride.  In fact your day might be better spent tuning your skis with a warm colored wax and saving gas money in hopes of improved conditions in the coming days. 

Additional Concern
  • 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

We have been tracking several types of buried weak layers over the last three weeks. Recent loading in the last 24hours in the form of rain combined with warm temperatures could be adding additional stress. A persistent slab is more likely to be triggered on very steep slopes and in places with a generally thinner snowpack like the Summit Lake area. This problem is becoming a bit of an outlier, but we do feel it is worth keeping in the back of your mind if you are thinking about venturing onto sustained steep slopes. 

Fri, January 9th, 2015

Yesterday a warm low-pressure system brought us temperatures into the 40’s F at sea level and rainline was near 3000′. Ridgetop winds were predominantly from the East averaging 30mph and .5 inches of rain was measured in Turnagain Pass and just over 1 € in Girdwood.

Today warm temperatures and very light rain will persist throughout the day. Rainline may creep down to about 1000′, but only a trace of new snow is expected to fall at higher elevations. Ridgetop winds are expected to be 20- 40mph from the East.

Warm temperatures and light precipitation will continue into the weekend with our next chance for cooler temperatures on Saturday night. Winds should be light to moderate from the East.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 38   0   0.5   30  
Summit Lake (1400′) 37   0   0.5   6  
Alyeska Mid (1700′) 37   0   1.17   23  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 31   E   29   64  
Seattle Ridge (2400′) 33   ENE   26   58
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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.