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Thu, April 7th, 2016 - 7:00AM
Fri, April 8th, 2016 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is  CONSIDERABLE  below 3000′ due to the potential of large destructive glide avalanches. There are several areas where glide cracks threaten poplar terrain and travel in these zones is discouraged. Cautious route-finding and terrain evaluation are essential to avoid being under the runout of glide cracks.

In the Alpine the avalanche danger is MODERATE above 2500′, where skier triggered wind slabs and wet avalanche are possible. This danger will depend on snow depths and will increase with solar exposure on specific terrain features.

*As glide avalanches continue to release, summer use trails with avalanche terrain above should be avoided. The Byron Glacier trail in Portage Valley is not recommended and the Turnagain Arm Trail between Bird and Girdwood, remains CLOSED.

Special Announcements

FREE rescue clinics and general avalanche information for those headed to Arctic Man this week.  Click  HERE  for more information.  The snowpack has been reported to be very unstable in the Hoodoos with many human triggered avalanches over the weekend. Please be on your guard and don’t forget your beacon, shovel and probe.

Thu, April 7th, 2016
Above 2,500'
2 - Moderate
Avalanche risk
3 - Considerable
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
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide avalanches continue to be the primary concern in the mid elevation band below 3000′. Many large glides have released this week leaving Turnagain Pass covered in dirty brown streaks. Yesterday two new glide avalanches were confirmed on Seattle Ridge and one new one on Pete’s South. The good news is glides can be avoided by simply not exposing yourself to the run-out zone of existing cracks. Unfortunately glide cracks do threaten popular terrain on both sides of the road. The Seattle Ridge snowmachine ‘uptrack’ being of most concern since it has a very large crack that extends into this zone. Since this is the only route to the back bowls of Seattle Creek, this proposes a challenging dilemma and should warrent a discussion within your group. The bottom line is, should you choose to go, limit your time in this zone, travel one at a time, and don’t high mark under this huge crack. If you were to be in the wrong place at the wrong time getting caught up in a glide avalanche will undoubtedly be unsurvivable.

This picture was taken on April 2, but still reflects similar conditions near the Seatte Ridge uptrack. 



Although glide avalanche frequency has decreased since this past weekend, there is still a lot of potential for more glide avalanches on Seattle Ridge.


New glide release on Pete’s South (middle one is new.) Photo by Tim Glassett

Avalanche Problem 2
  • 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

The possibility of wet loose avalanche activity will increase with warming daytime temperatures. In the mid elevation zone below 2000’ it will be important to monitor the surface crust. Due to recent rain showers and cloud cover this zone hasn’t been getting a good “re-freeze” overnight. Yesterday by 3:30pm the surface crust had completely disappeared and the snow was becoming very punchy causing skis to sink in 8-10”. Should you experience this today, stay off of slopes steeper than 35 degrees and avoid terrain traps.

In the Alpine, an estimated 4-8” new snow has fallen in the last two days, and deeper amounts are more likely on the Northern side of Turnagain Pass. Unfortunately, we do not have reliable precipitation data for Turnagain Pass right now, so it will be important to pay attention to how much new snow is sitting on the stout surface crust below. Triggering a wet/damp “point release” will increase with daytime temps and solar exposure. This avalanche problem will be minor if new snow depths are shallow. 

Additional Concern
  • 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

Yesterday moderate Easterly winds and variable snow showers were observed in Turnagain Pass with heavier precipitation observed on the Northern end of Turnagain Pass. Winds slabs up to 8-10” thick are possible on leeward terrain features in the alpine and could be tender on steeper slopes. Monitor snow depths, pay attention for shooting cracks and pillowed shape features in steep terrain.

Cornices:  We are still waiting for the Alpine to warm up enough to start seeing a natural cornice fall cycle.  We do know that cornices are close enough to failure that skiers or snowmachiners can influence a failure by travelling on a corniced ridge and the potential for a human-trigger is a very real concern.  Remember these have a tendency to break much further back than one might expect.

Thu, April 7th, 2016

Yesterday weather conditions were variable throughout the forecast zone. Continuous moderate rainfall was observed on the far Northern side of Turnagain Pass, North of Tincan. On the South side there was a mix of scattered rain/snow showers and intermittent periods of sun. Rain/snow line was near 1800′. Two inches of new snow was observed yesterday on Magnum mid day. Ridgetop winds were from the East average 15-25mph. Daytime temperatures reached 42F at Center Ridge Wx station (1800′) and overnight temperatures dipped into the low 30F’s for several hours.

Rain and snow showers should be anticipated again today, but with less precip, 1-2 € of snow in the Alpine. Rain/snow line will be around 1700′. Temperatures at 1000′ will be in the high 30F’s to low 40F’s. Ridgetop winds will be Light to Moderate from the East.

Tomorrow there’s talk of partly sunny skies before another low pressure moves into the area on Saturday, bringing another round of rain and snow showers.  

 ** The precip data at Center Ridge hasn’t been alligning with field observations over the last week. Also Turngain Pass DOT weather station is currently not functioning.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   rain   **0.1   116  
Summit Lake (1400′) 38   rain   0.1    35
Alyeska Mid (1700′) 34   rain   .29    102

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25   ENE   18   43  
Seattle Ridge (2400′) 28   SE   17   39  
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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.