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Tue, January 13th, 2015 - 7:00AM
Wed, January 14th, 2015 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

A MODERATE avalanche danger exists at all elevations in the backcountry. Naturally occurring glide avalanches and human triggered wet loose avalanches will be possible in the treeline elevation band (1,000′-2,500′). Above treeline, in the Alpine, human triggered fresh wind slab avalanches 8-16″ thick will be possible on wind loaded slopes.

Tue, January 13th, 2015
Above 2,500'
2 - Moderate
Avalanche risk
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
  • 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

Another warm, wet and windy storm is impacting the Eastern Turnagain Arm region once again. This system moved in yesterday afternoon and will be exiting today. So far we have seen just under an inch of rain up to 2,500′ with heavy wet snow above this. The rain has likely melted most surface crusts up to 2,500′, and possibly higher, and will continue to saturate the snowpack. This will create wet loose avalanche potential along with an increased glide avalanche potential.

Since the pack has already adjusted to rain up to 2,500′ from the last storm, it is not prime to produce significant natural wet avalanche activity. Yet, at the upper elevaitons we may see some shallow wet loose avalanches in the new snow as temperature climb slightly today. That said, human triggered wet loose snow avalanche will be possible on steep slopes where loose, unconsolidated and soggy snow exists. On sustained steep slopes these could be quite large. Avoiding steep terrain with unsupportable wet snow is recommended. 

Glide Avalanches:
We are currently in a “glide cycle” of sorts. We have seen widespread glide crack development through Turnagain Pass and Girdwood Valley during the past 3 days. Only a handful of these cracks have actually avalanched. Check out the comparison photo below put together by Heather Thamm. This shows that not all glide avalanches are preceded by a slowly opening crack. Something to keep in mind if you are headed out in the backcountry. This can make avoiding being under a glide avalanche more tricky, but most of the time they do have glide cracks present which are easy to recognize.


Avalanche Problem 2
  • 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

While it has been raining up to 2,500′, it has been snowing above this. I think it is safe to say that around 5-8″ of heavy to medium density snow exists and covers essentially the top 500-1,000′ or so of the ridgelines around Turnagain Pass. The new snow has come in with strong Easterly winds which has likely built wind slabs up to 8-16″ in depth. Another 2-4″ of snow is expected with moderate Easterly winds today which, if this is the case, add to the slabs from the past 24-hours. These will be sitting on a hard pre-existing crust and bonding of the new slabs to the older crust is uncertain. However, I’d expect with the warm temperatures, that these slabs should settle out rather quickly and be somewhat stubborn to trigger. 

If you are headed out in search of new snow at the high elevations, watching for red flags (recent avalanches, collapsing and cracking in the new snow) will be essential. Quick hand pits are an additional great way to see how the new snow is bonding.

Tue, January 13th, 2015

Light rain spread over our area yesterday with a more intense precipitation period overnight as a warm storm is slowly exiting the region. A total of 0.9″ of water has accumulated at the Center Ridge Snotel station as of this morning while Girdwood Valley has seen 0.7″ and Summit Lake recording no measureable precipitation. The rain/snow line was up to 2,500′ with temperatures close to 30F on the ridgetops and the upper 30’s F below treeline. Winds have been strong from the East, averaging 33mph with gusts over 70mph at the Sunburst weather station.

Today, 0.3-0.5″ of rain is expected to continue up to 2,500′, possibly higher, with 2-4″ of heavy snow above this. Temperatures should remain near 30F on the ridgetops and in the upper 30’s at and below treeline. Ridgetop winds will continue from an Easterly direction in the 20-25mph range.

As we head into the remainder of the week, a series of warm low pressure systems continue to spin in the Gulf bringing intermittent rain showers. The rain/snow line looks to remain near 2,500′ (or higher) through Thursday. Friday, cooler air does look to become mixed in and we may see the rain/snow line drop to 1,500′ or so for the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36   0   0.9   29  
Summit Lake (1400′) 37   0   0   5  
Alyeska Mid (1700′) 36 0   0.7   21.5  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   E   33   74  
Seattle Ridge (2400′) 30   NE   14   42
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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.