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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, November 22nd, 2016 - 7:00AM
Expires
Wed, November 23rd, 2016 - 7:00AM
Forecaster
Heather Thamm
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE  near and above treeline where triggering a slab 12-20 € thick is likely on all aspects above 2000′. This problem is due to a widespread layer of buried surface hoar. Triggering this layer will be more likely on slopes steeper than 30 degrees and especially dangerous on bigger slopes where slabs have the potential to be more connected and run further distances. A  MODERATE avalanche danger exists in the trees where an avalanche from above is possible.    

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

Special Announcements

Get your mind back in the ‘avalanche game’ by swinging by Blue and Gold Boardshop TONIGHT (Nov 22nd from 7-8:30pm) for a CNFAIC Fireside chat!! Topics covered: current snowpack conditions at Turnagain Pass, rescue techniques and internet resources. Details  HERE.

Tue, November 22nd, 2016
Alpine
Above 2,500'
3 - Considerable
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

A slab 12-20” thick is sitting on a fragile layer of buried surface hoar. This persistent weak layer is widespread and has been found on all aspect above treeline throughout Turnagain Pass and Summit Lake. Over fifteen human triggered avalanches were reported throughout the weekend and three more occurred yesterday on Tincan. Luckily no one has been buried or injured. Click HERE for more details on these observations.

 

 

Note worthy things to keep in mind today:

  1. Most of this activity has occurred in places that are known to be ‘safe terrain,’ like Manitoba’s West face and the standard skin track on Tincan.
  2. Many of these avalanches were triggered remotely, thus be extra aware of crossing under slopes above you.
  3. New snow and wind from Sunday has covered up avalanches that occurred Friday and Saturday, making it very difficult to know which slopes have slid.  
  4. Very little natural activity has been observed, with the exception of the West and South facing slopes on Lipps.

Although many of these avalanches have been relatively small, don’t forget that BIGGER SLOPES WILL HAVE BIGGER CONSIQUENCES! As we move away from the weather events that caused this scary set-up, remember this type of avalanche problem will be slow to heal. The next few days of clear weather are going to be tough to resist the temptation to get into bigger terrain.  Avoid high consequence terrain and keep your slope angles low.  Cautious route-finding and conservative decision-making will be necessary! 

 

This small avalanche was triggered remotely by two skiers putting in a skin track at 2200′ on a North aspect on Tincan yesterday.

 

Natural avalanche activity on the West face and South face of Lipps, as seen yesterday (Nov. 21) from the Johnson Pass Trailhead.

 

An 18″ crown from an avalanche remotely triggered near the top of Manitoba’s West Face on Sunday November 20. This was above an avalanche triggered in the same area on November 19th

 

Weather
Tue, November 22nd, 2016

Yesterday skies were partly cloudy following a storm that left 5 € of new snow in Turnagain Pass and brought moderate Easterly winds with gust into the 40’s mph. By mid afternoon ridgetop winds began to decrease into the teens mph. Rain/snow line briefly reached 1200′ yesterday morning, but temperatures cooled as skies cleared late morning. In the upper elevations temperatures averaged in the mid 20Fs.

Overnight winds were light from the East. Temperatures were in the mid to low 20’s F with a slight inversion causing ridgetop temperatures to be warmer than at road level. No precipitation was recorded.

Today skies are expected to be mostly clear with light winds from the East. Daytime temperatures will be in the high 20s F and no precipitation is expected today. This pattern is expected to last through Thanksgiving day with our next chance for snow showers near the end of the week.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   0    0 21  
Summit Lake (1400′) 26   0   0   2
Alyeska Mid (1700′) 31   0   0   4  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26   ENE 15 51  
Seattle Ridge (2400′) 26    n/a n/a    n/a
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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.