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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 15th, 2016 - 7:00AM
Expires
Sat, January 16th, 2016 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The mountains around Turnagain Pass have a generally LOW avalanche danger at all elevations.

*Remember, “low” does not mean “no” danger. Watch out for shallow wind slab avalanches in very steep and extreme terrain. Also, avoid being under glide cracks and avoid being on, or under, cornices. These hazards can be very manageable as long as they are on your radar.

Fri, January 15th, 2016
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
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
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

After the Holiday Storm Cycle pummeled the snowpack, initiated a widespread avalanche cycle and deposited over 10′ of snow in places, the snowpack has settled out and is now “generally” stable. This means triggering an avalanche is unlikely, with a few caveats:

1)  Glide cracks and cornices should be avoided. More on these below.

2)  Shallow fresh wind slabs and older lingering wind slabs are the most likely avalanche concern if you are headed to the “steep, gnarly and extreme” terrain around Turnagain Pass. As can be seen in the photos below, anytime there is snow in the mountains, there is always a chance for an avalanche in steep and complex terrain.

3)  Watch your sluff on steep slopes.

Photos below show a shallow wind slab that was triggered by, what looks to be, a snowmachine sized block of cornice (4,000′, W aspect in Lynx drainage). This is a good example of steep and complex terrain that may harbor small avalanches but with big consequences if you get knocked off your feet.

 

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

Numerous glide cracks litter the mid-elevations around Turnagain Pass. These continue to slowly open and although not many have released into full blown glide avalanches recently, they are still VERY much worth avoiding. If your route must take you under these cracks, travel quickly as they are unpredictable beasts and can avalanche at anytime, day or night, cold temperatures or warm. 

Please see these two observations sent in to us yesterday HERE and HERE. These are from folks that toured up and got a first-hand look at the devastation of a glide: “If you have any doubt about how powerful a glide crack avi can be check out the photos!” Quote by Ray Koleser. This particular glide avalanche occurred on the SW face of Lipps roughly one week ago (1/8-1/10).

Photos below taken by Ray Koleser of the Lipps glide avalanche. Looking up at the crown, recent snow has dusted over the bed surface and debris.

Looking down the slope at the debris, yellow line marks the toe of the debris.
 

Another look at the size of the debris field. This ran over a common area folks congregate to put their skins on.

 

Below is a time-lapse video taken by Ron Simenhois of a glide avalanche near Juneau. Images are at 5 min intervals and covers about 6 ½ hours in total. If you look closely, you can see the glide crack opening before the avalanche. Yup, these are nothing to mess with.

Additional Concern
  • Cornice
    Cornice
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

With mostly clear skies again today and a generally stable snowpack, don’t forget to give cornices an extra wide berth if you are headed for the upper elevations.

Weather
Fri, January 15th, 2016

Valley fog was the topic of the day yesterday. It reached as high as 2,000′ in places – but it was sunny above. Ridgetop winds have been light and variable for 3 days now, with the past 24-hours being light out of the East.  

Today, valley fog is expected again but could be a bit more patchy. Skies should remain mostly clear above the fog for the better part of the day with high clouds possible later in the day. Ridgetop winds are forecast to be light from the East then picking up to the 10-15mph range tonight.

For Saturday, a bump in Easterly winds and cloud cover is expected as a large low-pressure system spinning South of the Aleutians makes it way North.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25   0   0   83  
Summit Lake (1400′) 23 0   0   25  
Alyeska Mid (1700′) 26   0 0   61  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE   5   14  
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.