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Issued
Mon, March 7th, 2016 - 7:00AM
Expires
Tue, March 8th, 2016 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a MODERATE avalanche danger today at the Alpine elevations for shallow wind slabs, sluffs and cornice falls. Wind slabs 6-12″ thick may be found just off ridgelines. These could be lingering slabs or fresh slabs from today. At the mid-elevations, the danger is LOW where triggering an avalanche is unlikely. However, there are many glide cracks on easily accessed slopes – being aware of the cracks and avoiding being under them is recommended as they could avalanche on their own accord at any time.  

Mon, March 7th, 2016
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
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
  • 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

It was another spring-like day in the backcountry yesterday with bluebird skies and an opportunity for replenishing vitamin D stores. Today, cloud cover has moved back in but there could be some breaks here and there. We have 1-2″ of snow on tap with moderate Easterly winds. This is not enough snow to be a concern on its own but the reactive wind slabs from yesterday, as well as a bump in wind today, will keep wind slab avalanches on the docket. Loose snow sluffs and cornices will also remain on the docket.

Wind slabs:
Wind slabs that we are seeing and hearing about in the Turnagain Pass zone have been shallow 6-10″, scattered around ridgelines, and not packing too much punch. However, in the Girdwood Valley and North where more snow fell, slabs are reported to be thicker. 

If you are headed out today, watch for:

1) Stiff snow on the surface of the snowpack
2) Winds actively loading slopes (there may be just enough wind in the forecast to form fresh slabs at upper elevations)
3) Cracking in the snow around you
4) Surface texture and hints that slopes are wind loaded

Cornices!:  Give these a wide berth, wider than you think. 

Sluffs:  Watch your sluff. These are entraining several inches of surface snow and could get quite large in large terrain.

Photo below: Wind slab avalanche triggered by a skier yesterday. This avalanche was between the Magnum and Cornbiscuit ridgelines in an area called Superbowl. Skier was not caught and the slab itself was quite small, 6-10″ thick, yet did propagate down the ridge and entrain a bit of sluff as it ran.

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

As long as glide cracks keep moving and breaking up our snowpack we will keep mentioning them. The picture below shows an oblique view of the large cracks on Cornbiscuit’s SW face. Folks have been wisely staying out from under them and, in this particular case, putting the skin track on the NW ridge. 

We have not seen a glide avalanche in the Turnagain Pass zone for several days, however we do see these cracks continue to move and open. Limiting time under these, if your route must take you there, continues to be wise.

Photo: Oblique view of the glide cracks on Cornbiscuit’s SW face.

Weather
Mon, March 7th, 2016

Sunny skies greeted the many backcountry users along Turnagain pass yesterday. Winds were light from the Northeast on the highest peaks and it was downright warm with temperatures reaching 30F at the upper elevations and 45F along the road.  

Overnight, winds have bumped up slightly (10-15mph from the East) and cloud cover has moved in. There is a very weak disturbance moving over through the day and we could squeak out 1-2″ of snow above 1,000′ today, with rain below, and another 1-2″ tonight. Cloud cover could also break apart is areas, providing for better visibility. Winds are slated to remain moderate in the 15-20mph range from the East along the ridgelines. Temperatures should be warm again, mid 30’s at 1,000′ and the mid 20’s on the ridgetops.  

For Tuesday, another band of clouds and wind are on tap as a low pressure system in the Gulf moves North and begins to impact our region.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   0   0   137  
Summit Lake (1400′) 35   0   0   44  
Alyeska Mid (1700′) 32   0   0   108  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   NE   7   17  
Seattle Ridge (2400′) 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.