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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, January 29th, 2017 - 7:00AM
Expires
Mon, January 30th, 2017 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

There is a CONSIDERABLE avalanche danger above treeline in the mountains surrounding Turnagain Pass, Placer Valley and Johnson Pass. Human triggered slab avalanches 2-4′ in depth are likely in areas that have seen little traffic (prior to last week’s storms) and where a shallower snowpack exists (such as the South end of Turnagain Pass). These could be large and dangerous slides that break near the ground. These are the types of slabs that can be triggered remotely, meaning from the bottom/mid-slope or adjacent to the slope. In the trees, a MODERATE danger exists where triggering one of these slabs is possible. Below 1,000′ the danger is LOW where wet snow has now frozen into a hard crust.

Girdwood Valley:   Human triggered slab avalanches have the potential to be larger, and break near the ground, compared to Turnagain Pass due to more snow that has fallen on a weaker snowpack.  

Summit Lake: Dangerous avalanche conditions exist.  Please check out the Saturday Summit Summary  HERE.  

 

Special Announcements

Dangerous avalanche conditions exist in many areas around Southcentral Alaska
including the Southern Kenai Mountains,  Hatcher Pass and  Anchorage Front Range

  • There was a  confirmed snowmachine triggered avalanche accident in the Snug Harbor area yesterday that resulted in a fatality, limited information exists and we are gathering details currently. Our thoughts are with the family and friends.
  • The Southern Kenai Mountains, including Snug Harbor and Lost Lake zones have dangerous avalanche conditions. This region is out of the advisory area but received 3-5+ feet of snow in the past week and several avalanches have been observed.  
  • Click  HERE  for the Hatcher Pass Avalanche Center advisory and  HERE  for recent snowpack observations.

**Wherever you decide to venture today with the clearing skies remember:  Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential. Carry your rescue gear and practice safe travel protocol – such as exposing one person at a time, grouping up in safe zones, having escape routes planned and watching your partners!  Sticking to slopes under 30 degrees with nothing steeper above you can make for a safer day enjoying the new snow.

Sun, January 29th, 2017
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
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. 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
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

Cooling temperatures and clearing skies are a welcome relief to the overcast and low visibility conditions the past week. These better weather conditions will also allow for travel above treeline into the upper elevations – where the best powder exists from the past storms – this combination is our main concern at the avalanche center. Simply put, the snowpack is unstable in many areas and today could be a good day to get lured into steep avalanche terrain sporting good snow. What we have is a slab 2-4′ thick composed of last week’s storm snow (Jan 21 and Jan 26 storms). This slab sits on a variety of weak layers, most pronounced in the Girdwood Valley and the Southern end of Turnagain Pass, and further South. Several observers have noted widespread collapsing in the areas South of Turnagain Pass.

Careful snowpack evaluation is key today:

  1. Listen for whumphing (collapsing of the slab)
  2. Watch for cracks that shoot from your snowmachine, skis or snowboard
  3. Do you see any recent avalanches? 
  4. Can you feel weak sugary snow when you step down with your boot? Possibly not if the slab is 2-3′ thick where you are
  5. Is the snowpack thin in general? 

These are all good questions to be asking yourself. Keep in mind, these signs may not be present, especially in areas well traveled prior to the storms, but don’t let that sway you into thinking the steeper slope next door and less traveled is safe. Today could be a tricky day to truly assess if a slope will slide or not. Due to the potential for large un-survivable avalanches, hedging your bets and sticking to mellow slopes is recommended.

A couple other points to consider:

  1. Hand pits may not work as the slab is likely too thick
  2. Slope cutting and ski cutting is not recommended as the slab may break above you
  3. Remote triggering is possible (from below, mid-slope, adjacent to or from the ridgeline)

Low visibility and a thin snowpack exist on Magnum’s West face

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

Cornices have grown substantially with the Jan 26 warm storm. These could be teetering on the balance and if one breaks, is likely to trigger a potentailly large slab avalanche below. Please be careful along ridgelines as a cornice break could not only take you down, but a subsequent avalanche could overrun someone below you.

Weather
Sun, January 29th, 2017

Yesterday’s weather consisted of overcast and obscured skies with light snow flurries. Snow accumulation was a trace to 3″ depending on locations. Temperatures continued to be warm, in the upper 20’s to 30F in most locations. Winds were light with gusts into the 20’smph from the Northwest.

Overnight, skies have cleared and temperatures have dropped dramatically with a cold Northwest flow over the region. Currently temperatures sit in the single digits above 3,000′ and in the teens below this, where they are expected to remain today. Ridgetop winds are, and will be, light to moderate from the Northwest (5-15mph) with gusts into the 20-30mph. There is no precipitation expected and skies should be partly sunny.  

Tomorrow and Tuesday another system will move through bringing a chance for additional snow and warming temperatures before a possible dry spell for the later part of the work week. Stay tuned.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21   2   0.1   62  
Summit Lake (1400′) 17   0   0   26  
Alyeska Mid (1700′) 21   trace   0.02   54  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 13   NW   5   24  
Seattle Ridge (2400′) 15   Rimed   Rimed    Rimed
Observations
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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.
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