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Issued
Sun, November 22nd, 2015 - 7:00AM
Expires
Mon, November 23rd, 2015 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Sunday, November 22nd UPDATE:

After a series of storms dropped 8-10+” of snow late last week, skiers and snowboarders hit the backcountry yesterday (Saturday). What they found were VERY sensitive wind slabs; the winds not only blew during the storm, but continued on Saturday actively loading slopes. Several  human triggered avalanches  were reported  in the Turnagain Pass area (Details below).  

It is not unusual to have reactive wind slabs in this situation, but what is not as typical is what the slabs are sitting on – weak faceted snow (see video below).  This set up will take some time to stabilize. For today, and into this week, be VERY WARY of slopes harboring stiff wind drifted snow. The most concerning areas are steep and sustained terrain – where getting dragged down a chute or slope can have high consequences – not only for burial but for a rough ride.

Special Announcements

ADVISORIES?
We will begin issuing daily avalanche advisories for Turnagain Pass on Thanksgiving Day. Until then, we will continue to post intermittent updates.

Avalanche conditions OUTSIDE our forecast zone:
Hatcher Pass continues to have dangerous avalanche conditions. PLEASE see  hatcherpassavalanchecenter.org  !!


*The Tincan Snow Study Plot is installed and soon to be online! We need your help keeping this site undisturbed (people and dogs). Brief report and photos  HERE.

Sun, November 22nd, 2015
Alpine
Above 2,500'
0 - No Rating
Avalanche risk
Treeline
1,000'-2,500'
0 - No Rating
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. 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

Below are several photos from yesterday’s active avalanche conditions. You can read reports for these, and more, on our observations page – thank you to the folks for passing on their information!

As mentioned above, we have a ‘classic’ WIND SLAB avalanche problem out in the mountains. These slabs are scattered about and vary in thickness from 10″ to 2′. The trick is, some of them sit on weak faceted snow and others do not; meaning some slabs will be reactive (avalanche if the slope is steep enough) and others will not. The best method to avoid an avalanche will be avoiding wind loaded slopes – for a while. Unfortunately, facets under a slab can take days or weeks to stabilize, patience is warranted. Another trick is finding areas that were sheltered from the wind, this is where conditions are safer, however this is difficult since the wind found its way into the trees as well. 

Things to watch for:
1) Wind drifted snow, stiffer snow with a smooth rounded shape. 2) Shooting cracks (great photo sent to us below). 3) ‘Whoomphing‘ 

Photo below: Snowboarder triggered avalanche on Tincan, just above treeline (no one was caught).

 

Left photo: Test slope triggered by skier on bottom left.  Right photo: Shooting crack right after test slope failed (Ted Grosgebauer).
  

 

Observations
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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.