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

Today the avalanche danger is MODERATE both at Treeline and in the Alpine. Triggering a fresh windslab 4-8 € thick is possible today near ridgetops and on leeward features. Be on the look out for hollow sounding snow, shooting cracks, and blowing snow. Be aware of large cornice features and recent glide crack movement and avoid putting yourself on or under these unpredictable hazards.

Below 1000′ the avalanche danger is LOW where triggering an avalanche on a hard supportable crust is unlikely.

*Outside of our forecast zone in Summit Lake where a generally thinner snowpack exists triggering a slab 3′ thick is a concern. Cautious route-finding and careful snowpack evaluation is advised.  

Special Announcements

The Hatcher Pass Avalanche Center has completed an avalanche accident report following the recent death of a snowmachiner that occurred on January 2nd. Click HERE for the report.

Tonight Wendy Wagner, CNFAIC forecaster and director, will be giving our final Fireside Chat on snowpack and weather. It will be in Anchorage at the Alaska Avalanche School at 6:30pm.

On Saturday CNFAIC forecasters are hosting a Hands-on Avalanche Rescue Workshop from 11:00am to 12:30pm at the motorized lot on Turnagain Pass.

*All events are free to the public!  

Filing for the PFD this week? Remember, The Friends of the CNFAIC is part of  PICK.CLICK.GIVE. Your donations are greatly appreciated and an integral part to making the CNFAIC possible and sustainable.

Thu, January 7th, 2016
Above 2,500'
2 - Moderate
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Dangerous avalanche conditions. 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
  • 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

Overnight Easterly winds increased into the 20’s with gusts in the 30-40’s mph and moderate winds are expected to continue today. With 6-10” of low-density surface snow available for transport, isolated winds slabs are possible on leeward features. These slabs are expected to be small (4-8” thick), but if triggered in steep terrain, could send you for an unintentional ride.

Older winds slabs from the holiday storm event may still be lingering in very steep terrain, but otherwise this problem is becoming less likely as we move away from the storm. Yesterday a generally stable snowpack was observed where older wind affected snow was stabilizing quickly.

Ease into steep terrain today and pay attention for hard hollow sounding snow and shooting cracks. If you see snow being transported off of ridges be very aware of the consequences below you. 

Avalanche Problem 2
  • Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Today’s secondary concern is Cornice Fall and Glide Cracks!

Very large cornice features have formed throughout the region as a result of a two-week storm that deposited ~9’ of snow and was accompanied by very high winds. Cornices have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren’t accidently traveling on overhanging snow. 

Glide cracks are appearing throughout the forecast region (Girdwood to Turnagain Pass.) These cracks appear to be opening fast and are very unpredictable. Similar to managing a cornice, it is best to avoid traveling on or under slopes with glide cracks. Although triggering one of these is uncommon, should one release above you, consequences would be high. 

Significant moat at least 5 meters back from cornice on Seattle Ridge near the top of uptrack. At least one sled track took a quick dip. Photo by Paul Forward


Ski tracks above two glide cracks on Lipps SW face. These glide crack have recently opened and were not present a week ago.


Additional Concern
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

In some parts of the advisory area 5-7′ of settled storm snow is sitting on a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This is a low probability, very high consequence set-up.  It is important to use safe travel practices and do not overload slopes with multiple skiers, boarders or snowmachines. Limit your exposure time spent underneath large paths.

On the Sourthern periphey of our forecast zone such as Johnson Pass and Lynx Creek we have limited snowpack information. But we do know in Summit Lake, the snowpack is shallower and harbors more weak layers under the recent storm snow.  See Wendy’s observation and write-up from a snowboarder-triggered avalanche (Saturday) that failed on a buried surface hoar layer.

Watch for signs of instability: recent avalanches, shooting cracks, collapsing and whumpfing. Pay attention to snow depth and trigger points. Deep slabs are most easily triggered from shallow spots where the weight of the traveler can more easily affect the weak layer. 

Thu, January 7th, 2016

Yesterday skies were clear and temperatures were in the 20’s F. Light ridgetop winds were from the West.

Overnight Easterly winds increased into the 20’s mph. This morning increasing temperatures were 32F at 1000′ at Turnagain Pass. No precipitation was recorded overnight.

Today showery conditions are forecasted for mountain areas near the coast. This will likely be light rain below 1000′ near Girdwood and Portage and periods of light flurries are possible today in Turnagain Pass. Not much accumulation is expected. Easterly Ridgetop winds will remain in 15-30mph range throughout the day.

Friday night into Saturday another storm is expected to bring warm temps and more precipitation.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   0   0   83  
Summit Lake (1400′) 25   0   0   26  
Alyeska Mid (1700′) 28   0   0   61  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23    NE 11   40  
Seattle Ridge (2400′) 25   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.