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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, January 29th, 2015 - 7:00AM
Expires
Fri, January 30th, 2015 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

The avalanche danger is LOW today at all aspects and elevations as weak, incoming weather isn’t expected to significantly add to current concerns.   Pockets of MODERATE danger may exist particularly on upper elevation, west aspects where an older wind slab (3-6 €) could be tickled out.

If precipitation or winds enter the picture in amounts greater than forecasted, small and shallow (5-10 €) wind slabs late in the day could be a concern where active loading is taking place.

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Thu, January 29th, 2015
Alpine
Above 2,500'
1 - Low
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. 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

We’ve received great info from a Level 3 avalanche class that has been conducting fieldwork in both Turnagain pass and Summit Lake area over the last several days.  Students yesterday found a generally strong snowpack with shallow, stubborn wind slabs on Seattle ridge (Sunny side) that would not propagate under a skier’s weight.  Across the road where moderate westerly winds have not been so destructive the surface consisted of 2-4” of near surface facets capped by growing surface hoar yesterday.  Below the surface data and a lack of avalanche activity continues to validate the high strength, low propagation potential in the Turnagain pass area.

In terms of moving through the mountains today, any pockets of instabilities observed should be relegated to the upper 3-6” of the snowpack and will likely be in the form of older, shallow wind slabs on leeward slopes.  Look for these pockets of denser snow and be mindful of your terrain choices, weighing the consequences of popping off a shallow wind slab.  This will be particularly important in steep, (greater than 40 degrees) upper elevations where you may be exposed to terrain traps below.  If we receive more than 4” of snow today and winds kick up enough to actively transport snow, expect shallow wind slabs (5-10”) to be more reactive to human triggers.  

With a few inches of snow in the forecast, any new wind slabs could also prove problematic to ice climbers exposed to funneled terrain in areas such as Portage Valley.

Avalanche Problem 2
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

Glide avalanches are still littered throughout the forecast area and with a bit of a warm-up today we’ll be keeping an eye on any glide crack movement or release.  Your best bet remains to limit your time spent underneath glide cracks, as they remain an unpredictable beast.

Glide cracks and glide avalanches (already released) litter the South and West aspects of Eddies.  

  photo: Jaime Andersen

 

Low snow coverage:

Below 2000’ low snow coverage is deceiving with only a few inches of new snow covering rocks, ice and vegetation. Take your time getting in and out of the alpine today.

Weather
Thu, January 29th, 2015

Valley fog persisted throughout the day yesterday with mostly sunny skies above about 500′.   Temperatures warmed slightly throughout the day to the low-20’s at ridgetop locations.   Winds were light and variable, generally in the single digits through the daylight hours.

Today temperatures are expected to continue to climb to the mid-20’s at ridgetops with easterly winds in the 4-14mph range.   A weak band of increased clouds and precipitation is trying to push into our region today and it’s likely we’ll see 1-3 € of snow in the eastern Turnagain arm region by nightfall.

By Friday afternoon skies are expected to clear with high pressure, sunshine and dry offshore flow dominating our weather through the weekend.    

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 23   0   0   31  
Summit Lake (1400′)  15 0   0    6
Alyeska Mid (1700′)  18  0  0  22

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  19  NE  7 17  
Seattle Ridge (2400′)  20  variable 4   13  
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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.