Turnagain Pass RSS

ARCHIVED - Forecasts expire after 24 hours.
Sun, March 4th, 2018 - 7:00AM
Mon, March 5th, 2018 - 7:00AM
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is  MODERATE  above 1000′ on all aspects. Lingering wind slabs (up to a foot thick) will be possible to trigger along with a larger slab avalanche (up to 2′ or more thick) that breaks in weak layers deeper in the snowpack. Sunshine today may trigger small wet loose avalanches on steep Southerly aspects.  

**If headed South of Turnagain Pass be aware of recent avalanche activity in Summit Lake and Lost Lake areas. Click  HERE  for the Summit Summary and click  HERE  for several observations from Lost Lake.  

Special Announcements

Elevated avalanche danger exists in many areas of Southcentral Alaska including  Lost Lake  on the Kenai, the  Western Chugach,  Hatcher Pass, and parts of the Alaska Range. Recent natural and human triggered avalanches have occurred this week due to new snow and strong winds region wide; more snow is expected in the Anchorage and Mat-Su areas this weekend.

Sun, March 4th, 2018
Above 2,500'
2 - Moderate
Avalanche risk
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. 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
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Finding and triggering a slab avalanche that breaks in weak snow 1-2+’ deep in the pack remains a concern. This could be in the form of a lingering wind slab or a much older slab that sits on weak layers in the mid-pack. Although today’s clear skies should reveal a dusting of new snow from yesterday, this is likely only enough to obscure a generally variable and wind affected surface through the region. With a longer sunny day ahead, here are the things to keep in mind:

Lingering wind slabs:  Strong Northwest winds impacted the region last week and due to unusual wind loading patterns, formed hard wind slabs on a variety of aspects. Watch for steep areas harboring stiff snow over softer snow and cracks that shoot out from you. Old wind slabs can be found along ridgelines and in steep rocky terrain, but also mid-slope in cross-loaded gullies. Even a small slab can have high consequences in steep and committing terrain. 

Persistent slabs:  Several weak layers sit in the middle and base of the snowpack and as recent as last Tuesday, skiers triggered a large ‘persistent slab’ in the Summit Lake area. This problem has shown to be more pronounced on the Southern end of Turnagain Pass and Summit Lake where the snowpack is shallower (areas to the North, such as Crow Pass, could also be suspect). Wednesday, during the wind event, numerous large avalanches released naturally near Silvertip Creek and in Summit Lake, most likely due to winds overloading these various weak layers. In short, buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and buried surface hoar at the higher elevationsWhumpfing has been widely reported in the mid elevation band region-wide. If headed out for a long day in the mountains, remember these layers are there and no red flags may be present before a slab releases. 

Solar warming/effects:  Sunshine today along with light winds may allow for enough warming to initiate small wet loose avalanches on steep Southerly aspects. Warming may also cause slabs to be more reactive; something to keep in mind as we choose our late afternoon terrain.  

A wide angle view of Sunburst, Magnum, Cornbiscuit and Lipps – it may be March, but a generally thin snow cover remains


Weak layers in the snowpack at the mid-elevations on the South end of Seattle Ridge


Sun, March 4th, 2018

Overcast skies and snow flurries were over the region yesterday, with a trace of snow accumulating. Temperatures were in the upper 20’sF at 1,000′ and around 20F along ridgelines. Ridgetop winds were light and variable during the day before shifting Northwesterly overnight and picking up to the 5-10mph range. Temperatures also cooled to the teens overnight with colder air moving in.

Today, Sunday, we are expecting mostly sunny skies with light Northwest ridgetop winds (5-10mph). Temperatures are expected to rise to 30F at 1,000′ and to the mid-20’sF along ridgelines.  

Tomorrow, Monday, clouds move back in with another chance for snow flurries (little accumulation). The big news is later this week, a larger low-pressure system is forecast to move into the Gulf of Alaska. This could bring a much better chance for snowfall to the Turnagain area and Western Prince William Sound. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   trace   0   68  
Summit Lake (1400′) 18   0   0   28  
Alyeska Mid (1700′) 23   trace    0.02 60  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16   W   6    21
Seattle Ridge (2400′) 20   NW   7     20  
Recent Observations for Turnagain Pass
Date Region Location
11/16/23 Turnagain Observation: Tincan Common
11/14/23 Turnagain Observation: Sunburst/Magnum
11/14/23 Turnagain Observation: Seattle Ridge
11/13/23 Turnagain Avalanche: Tincan Trees
11/12/23 Turnagain Observation: Sunburst
11/12/23 Turnagain Avalanche: Goldpan – avalanche
11/11/23 Turnagain Observation: Tincan Common
11/11/23 Turnagain Observation: Taylor Pass – Sunburst
11/10/23 Turnagain Observation: Tincan
11/10/23 Turnagain Observation: Tincan Trees
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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.