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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, November 26th, 2016 - 7:00AM
Expires
Sun, November 27th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger is MODERATE  in both the alpine and at treeline on all aspects due to a widespread layer of buried surface hoar. Human triggered slab avalanches 10-20 € thick are possible. Be extra aware of changing weather conditions and any additional stress being added to the snowpack today. If the forecasted wind and snow start early expect the hazard to bump back up to CONSIDERABLE. Caution and safe travel protocol is advised if venturing in the backcountry.  Avoid travel underneath glide cracks.  

***Observations from the Summit Lake area on the Kenai are showing a similar snowpack. Weekly summaries will begin on December 2nd.

Special Announcements

Motorized use on Turnagain Pass is closed due to insufficient snow cover.  Please see riding area status at the bottom of this page for the most up-to-date information.

Snowmachine Specific €“ Avalanche Awareness and Rescue at AMDS
November 30 @ 6:30 pm – 8:00 pm | FREE
Join CNFAIC forecasters at Alaska Mining and Diving Supply for a discussion on Avalanche Awareness and Rescue. Topics addressed will be:

  • Recognizing safe zones vs. avalanche terrain, not always as simple as it sounds €¦
  • Situational awareness €“ clues to watch for to help determine an unstable snowpack
  • Rescue €“ what’s new with rescue gear (i.e., airbags) and what really saves lives
  • Backcountry responsibility €“ it’s not just our group out there

We hope to see you and your riding buddies Wednesday, Nov 30th from 6:30 till 8:00pm!!!

Sat, November 26th, 2016
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
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
  • 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

Yesterday was the second day since the surface hoar was buried on November 17th that we haven’t received any reports of human triggered slab avalanches in Turnagain Pass. With time this layer of buried surface hoar is becoming more stubborn and less reactive but this also means the slab has the potential to fracture once well onto the slope. This layer hasn’t gone away and still needs to be a major factor in slope choice. Remember buried surface hoar is persistent weak layer and human triggered avalanches are still possible. Observations around Turnagain pass continue to show that this layer is widespread throughout the terrain. Dozens of human triggered and remote triggered avalanches have occurred since November 17th on the popular slopes of Tincan, Sunburst, and Magnum. These avalanches have been small to medium in size; just large enough to bury a person or seriously injure you in a ride. Larger and/or steeper, more wind-loaded slopes that haven’t been ridden still have potential to avalanche and could have high consequences because of this weak layer. This is important to keep in mind today and throughout the weekend with more snow heading our way. Today new snow and wind increasing late in the afternoon may cause the danger level to rise. Pay attention to changing conditions, additional load will only make the consequences even larger. Be on the lookout for obvious signs of instability like blowing snow, shooting cracks and whumphing sounds.  In addition new snow and wind will be loading weak surface snow (new layer of surface hoar and near surface facets) that has developed over the past few cold clear days and may be reactive at this interface as well.

With the holiday weekend there could be more people heading into the backcountry. Be extra aware of other groups above and below you and only expose one person on a slope at a time.

National Avalanche Center Danger Scale tutorial: HERE.

Buried surface hoar found easily in a snow pit on Tincan yesterday at 2700′. Photo: Andy Moderow  

Avalanche Problem 2
  • 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

There were two glide avalanches reported on November 23rd and other glide cracks have been observed around Turnagain and Summit area. If you see a glide crack give these a wide berth, minimize time spent underneath, and remember these are totally unpredictable. They are not triggered by humans and are the entire snowpack releasing. These will also be hard to see when covered up by new snow and wind loading. 

 

Glide crack opening on the face of Common Bowl on Tincan. Photo: Andy Moderow

 

Weather
Sat, November 26th, 2016

…WINTER WEATHER ADVISORY FOR BLOWING SNOW REMAINS IN EFFECT
FROM 5 PM THIS AFTERNOON TO 5 AM AKST SUNDAY THROUGH TURNAGAIN
PASS AND PORTAGE VALLEY… See link HERE for more details.

Yesterday started with light snow in the morning with a inch of accumulation. Skies cleared in the afternoon and valley fog moved in late in the day. Temperatures were in the low 20Fs. Winds blew easterly in the 20s in the morning and shifted to northerly and light in the afternoon. Overnight the temperatures dipped into the teens and the winds were light.

Today will be partly to mostly cloudy as the storm approaches. Snow is expected to start this afternoon and winds are forecasted to pick up gusting into the 30s from the SE. 0-3″ of snow is possible. Temperatures should rise to the high 20Fs. Tonight the snowfall and wind will continue with 5-10 inches forecasted to fall and gusts into the 40s. Temperatures should remain in the 20s.  

Tomorrow temperatures should dip back down to low 20Fs. Winds should become light and northerly and there is still a chance of light snow. There is a bit of clearing trend into the middle of the week and then more snow on tap for the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 19   1   .1    18
Summit Lake (1400′) 21   1 .1  3
Alyeska Mid (1700′) 20 0 0  3

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  n/a n/a   n/a   n/a  
Seattle Ridge (2400′)  16 variable   15    30
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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.