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Fri, April 8th, 2016 - 7:00AM
Sat, April 9th, 2016 - 7:00AM
Graham Predeger
Avalanche risk The Bottom Line

There is a generally LOW avalanche danger throughout Turnagain Pass for our typical avalanche problems.  The one exception continues to be glide avalanches in the mid-elevation and is why the danger is CONSIDERABLE between 1,000′ and 2,500′ in elevation.   Cautious route finding and terrain evaluation are essential to  avoid being under the runout of glide cracks.

*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

The Chugach National Forest will be closing some riding areas to motorized use today due to snow melting out.  Please see the table at the bottom of this page for a complete list.  Snug Harbor, Summit Lake and Turnagain Pass (N. of Granite creek) will remain open.  

Fri, April 8th, 2016
Above 2,500'
1 - Low
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 elevations extending as high as 3000′. Many large glides have released this week leaving Turnagain Pass covered in dirty brown streaks.  New glide avalanches were reported in both the Girdwood Valley, Seattle creek drainage and Seattle ridge overnight (see below), leaving us no doubt that this is still a very dangerous avalanche problem.  Seattle ridge just above the Seward highway appears to be the epicenter of Glide activity, and still harbors large cracks that have yet to release.  If travelling in the vicinity of glide cracks today, travel fast and limit your exposure time or better yet, avoid cracks and runout zones all together.

‘Repeat Offender’ slide path as seen from the DOT RWIS camera this morning.  A large crack failed (and avalanched) overnight near or possibly covering the common snowmachine up-track.  There is still a lot of well-travelled terrain threatened by glide cracks that have not avalanched yet.

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

Warming daytime temperatures and direct sun today will increase the likelihood of wet avalanches in the afternoon below 3,000′.  It’ll be prudent to keep an eye on your boot penetration throughout the day.  Stay off of steep slopes (greater than 35 degrees) where you are post holing up to your crotch.  Boot penetration is an informal test, but it does give a good idea of just how deep the ‘rot’ goes.  Yesterday afternoon, the surface was unsupportable up to at least 2,200’ and likely higher.  Any wet loose avalanches triggered today are likely to be on the smaller scale but could prove troublesome if coupled with a terrain trap.  Formation of fresh roller balls will be a good clue that the surface is losing strength and a good indicator of wet avalanche activity on steep slopes.  

Roller balls forming late in the day often act as a precurser to wet avalanche activity.

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

Moderate easterly winds and intermittent snow showers over the last several days have built shallow wind slabs (12-18”) in the alpine.  Given the firm melt-freeze crust deposited to ridgetop last week, these shallow wind slabs have potential to be touchy in steep, unsupported terrain.

Cornices:  They continue to cling to ridges.  Likely triggers today could take the form of skiers, snowmachiners or warming temperatures and direct sun.  Stay well away from the edge of corniced ridges as these have a tendency to break much further back than you may expect.

Fri, April 8th, 2016

Mostly clear skies graced the eastern Turnagain arm region yesterday with temperatures averaging 38 degrees at Center ridge (1,880′).   Winds were light for most of the day and transitioned to outflow (WNW) by mid-morning.   No new precipitation was recorded.

Today patchy morning fog along Turnagain arm and the Portage valley should give way to clearing skies.  Ridgetop winds will be in the 10 – 20mph range from the North before picking up and transitioning to an Easterly this evening with the approach of our next weather disturbance overnight and through the weekend.  Temps today are expected to be in the 35 -40 degree range at 1,000′.  No new precipitation is expected today though it looks like a return to a showery pattern through the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 38   0   0   116  
Summit Lake (1400′) 39    0 0   35  
Alyeska Mid (1700′)  36  0 0   102  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  27 WNW   7   21  
Seattle Ridge (2400′) 31   WNW   5    22
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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.