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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, March 11th, 2016 - 7:00AM
Expires
Sat, March 12th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is  MODERATE  today above 1000′. Glide cracks continue to release naturally and without warning and threaten a lot of mid-elevation terrain. Identify slopes with glide cracks and avoid being within the runout of a glide. Changing conditions today in the Alpine will make it possible to trigger fresh wind slabs and loose snow avalanches. Avoid travel on or under large cornices.  

* Similar avalanche conditions exist in the Summit Lake area, but the snowpack  is more complex and variable. Click  HERE  for a video and observation from Wednesday that shows an additional concern to be aware of.  

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Fri, March 11th, 2016
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
No Rating (0)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
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

In the Alpine be on the lookout for a variety of surface snow instabilities and changing conditions as a storm system moves over the region.

Wind Slabs: Today new snow and sustained ridgetop winds may combine to form fresh, tender wind slabs in leeward areas. Look for pillowed snow, drifts and shooting cracks. These new slabs may break easily and catch you up, especially in steep terrain. Check out the FS National Avalanche Center’s Wind Slab tutorial HERE. The new snow is falling on a variety of surfaces and may not bond well. 

Loose snow: On shaded aspects dry loose snow sluffing will warrant management in steep terrain.  Sluffs have been fast moving with the ability to entrain a significant amount of surface snow in big terrain. Any new snow will add to the potential and may create this hazard on solar aspects as well if the new snow does not stick to the sun crust. 

Cornice falls: Very large cornice features can be found along most ridgetops throughout the advisory area. Cornices have a tendency to break further back than expected. Give them lots of space, and limit time under them. Should you get too close, a snowmachine or person could tip the balance.  The recent fatality of an avalanche professional in Oregon due to a large cornice fall is again a tragic reminder of how dangerous these can be, especially in high consequence terrain. Additional loading today may make cornices more touchy.

Wind loading on the Tincan ridgeline yesterday afternoon.

 

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

AVOID travel under glide cracks. This week has been a particularly active glide avalanche cycle. Glide cracks continue to threaten large areas of terrain throughout Turnagain Pass, Girdwood, and Summit Lake. There were several new glide avalanches seen Wednesday from the Seward Hwy, and a large glide released on the East face of Seattle Ridge a few days ago. Glide cracks are on all aspects within the mid-elevation band (1000′-2500′), and some areas like the SW face of Cornbiscuit and Tincan are covered. This avalanche problem is impossible to predict and is not associated with human triggers. We have been talking about the glide avalanche problem for over two months in the advisory and as long as glide cracks continue to open up, move and release, we will stress the importance of avoiding them. Click HERE for a forecaster video about glides from yesterday on Turnagain Pass. We really want to avoid any human involvement with a large glide avalanche!

Some important things to remember:

1) What the heck are we talking about?

Glide Avalanches (definition from the FS National Avalanche Center Encyclopedia): Glide occurs when the entire snowpack slowly slides as a unit on the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow and pose a hazard that is very difficult to forecast. They are often preceded by glide cracks (full depth cracks in the snowpack), though the time between the appearance of a crack and an avalanche can vary between seconds and months. 

2) We really do not understand when they will release. Unfortunately there are no rules of thumb to give. They release during the day and at night, with cooling, with warming, during storms and after storms, on sunny slopes and shaded slopes. The only way to manage the uncertainty is to avoid time spent underneath. Travel in places like Bertha creek under the South face of Cornbiscuit could be particularly hazardous due to being in a tight terrain trap if one releases from above and buries you in the drainage.

3) Just because one glide released on the slope it doesn’t mean others won’t. Many cracks only partially release and then have additional hangfire or the potential to release more. The glide avalanche on Pyramid is great example of this. Click HERE for the 2/28 observation of the initial release and HERE for 3/7 observation of the additional piece.

4) This is an unusual string of glide cycles and an unusual winter. The glide cracks and avalanches aren’t related to other avalanches problems. They are not Wet slabs or Deep slabs. This can be confusing. They are a separate hazard that needs special consideration. Avoid skinning, skiing, hill climbing, parking or picnicking underneath.

This photo from Wednesday is worth reposting today. This is the glide hazard that threatens the Bertha Creek drainage.  Photo: Liz Repetto

 

 

Weather
Fri, March 11th, 2016

Yesterday was mostly sunny in the morning with clouds building in the afternoon. Winds picked up overnight gusting into the 50s from the east. Temperatures were in the mid 20Fs to high 30Fs. A couple inches of snow fell on Turnagain Pass overnight.  

Today will be mostly cloudy with snow showers. 3-6″ of snow is forecasted to fall throughout the day. Winds will be easterly, 15-30 mph with higher gusts. Temperatures will be in the mid 20Fs to mid 30Fs.  

The snow showers will continue tonight and taper off tomorrow with some sunshine on tap for the weekend as a ridge of high pressure moves over Southcentral Alaska.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   2    .2 134  
Summit Lake (1400′) 33 0    0  43
Alyeska Mid (1700′) 32  trace trace    105

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  23 ENE   25   55  
Seattle Ridge (2400′)  25 SE   15    37
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Riding Areas
Updated Mon, December 02nd, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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