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Thu, January 26th, 2017 - 7:00AM
Fri, January 27th, 2017 - 7:00AM
Heather Thamm
Avalanche risk The Bottom Line

An  Avalanche Warning  has been issued for Turnagain Pass, the Kenai Mountains and Western Chugach Mountains and will remain in effect today through 6am tomorrow, Jan.26th.  Heavy snowfall, rain and strong winds are creating a HIGH avalanche danger at all elevations in Turnagain Pass today. A HIGH avalanche danger also exists in Portage, Placer and Girdwood Valley where natural avalanche 3-4′ thick are likely today.  Travel is not recommended in avalanche terrain where natural avalanches are likely occurring due to rapid loading. Later in the day as heavy snow and rain start to diminish human triggered avalanches will remain very likely. Should you decide to check out the conditions keep slope angles less than 30 degrees and steer clear of gullies and the bottom of large and steep slopes in the event an avalanche occurs above you.

Special Announcements

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

  • There will be intermittent traffic delays Thursday January 26, on the Seward Highway for avalanche hazard reduction work between Bird and Portage near mileposts 100 to 80.   Motorists should expect delays of up to 1 hour between  10:00 AM and 2:00 PM.
  • The Southern Kenai Mountains, including the Lost Lake zone is expected to have dangerous avalanche conditions today also. This region is out of the advisory area but received 3-5 feet of snow from Saturday’s storm and another an estimated 2-3′ today. There were several avalanches observed over the weekend and more are likely today.  
Thu, January 26th, 2017
Above 2,500'
4 - High
Avalanche risk
4 - High
Avalanche risk
Below Treeline
Below 1,000'
4 - High
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
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

New snow and wind have combined to create very unstable slabs 1-3’ range.  Ridgetop winds from the East (SE to NE) have picked up into the 40’s and 50’s mph overnight with serval gusts in the 90’s at Sunburst weather station last night. An additional 10-12” of snow is forecasted for the higher elevations today and will increase the size of these slabs. These slabs will release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be extra important to avoid being near any runout zones today. Avoid places like Johnson Pass where an avalanche could cross the trail. Rapid loading due to heavy snow and strong winds will continue through late morning. Gusty winds are expected through early evening as precipitation dimishes by early afternoon – these winds will make natural avalanche activity likely throughout the day. 

This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” this problem today. 

Photo of W facing slopes of Eddies following a wind event on Monday into Tuesday that loaded SW aspects. SW aspects will be more loaded today and it will be important to keep your distance from the runout of slopes steeper than 30 degrees.  Photo by Mike Ausman 


Avalanche Problem 2
  • 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

A variety of weak snow (facets and buried surface hoar) that sit near the ground or mid-pack remain the most concerning layers today. Avalanches occurring in the upper layers have the potential to step down and release the entire snowpack in some places. Girdwood Valley and Johnson Pass area have more potential for this to occur where a generally thinner and weaker snowpack exist. In cases where this happens, the volume will be large, could run long distances and potential for burial, if caught, is high.  Avalanches occurring at this layer have a high propagation potential, which means that fractures can and will travel across slopes. 

Because of this travel in avalanche terrain is not recommended today including being in the run-out of a steep slope.  Since this problem exists at all elevations, it will be important to avoid the runout of terrain from above when traveling in the flats like in the flats below Seattle Ridge. 

An Eastern facing bowl on Raddedtop that released to the ground sometime on Monday during a period with strong winds and snowfall. This is a good example of a thin snowpack in parts of the Girdwood Valley. The debris from this avalanche was is estimated to have run about 1000′.

Additional Concern
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Rain falling on snow to 1,000’ will weaken the surface snow and possibly an older layer beneath. Wet loose avalanches are likely and wet slab avalanches are possible due to a layer of buried surface hoar 1-2’ below the surface. In channeled terrain an avalanche from above will likely entrain weak snow in the lower elevations increasing overall volume. Don’t under estimate small terrain features with high consequences. Triggering a wet slab in the lower elevations of Twenty mile or Placer could have high consequences if pushed into or over terrain traps such as cliffs, gullies, or trees. Again it will be important to avoid steep terrain and maintain a conservative distance from all run-out zones. 

Thu, January 26th, 2017

Yesterday above freezing temperatures were observed along Turnagain Pass with light rain late afternoon. Moderate Easterly ridge top winds increased to strong in the afternoon. By early evening winds were averaging in the 40-50’s mph with several gust in the 90 mph’s on Sunburst weather station. Overnight about 12 € of snow fell in upper elevations (1.3 € H2O) in Turngain Pass and Girdwood.  

Today as an intense front moves through our region heavy precipitation is expected to last through late morning, this is snow above 1000′. Strong Easterly ridgetop winds will diminish to moderate (15-25mph) by late afternoon, but expect gusts to still be in the 40’s mph. Expect above freezing temperatures near sea level today and rain/snow line could be as high as 1000′.  

Tonight temperatures are expected to cool off bringing snow to lower elevations. Another low pressure system centered over the Bering is expected to move through our area Friday and into the weekend with another chance for snow fall.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′)  34 12   1.3   61  
Summit Lake (1400′) 34   1   .2   23  
Alyeska Mid (1700′) 32   11   1.3   59  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE   39   94  
Seattle Ridge (2400′) 26   SE   27   71  
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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.