|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.
|Size (D scale)
|Unlikely to bury a person
|Can bury a person
|Can destroy a house
|4 & 5
|Can destroy part or all of a village
We like to think of the danger scale on a continuum and we have inched our way towards LOW in Turnagain Pass. Slope testers (skiers and riders) have been in full force over the last week pushing further into the mountains. There have been a handful of slabs triggered without incident this week and it’s not impossible to find unstable snow. Keep the following problems in mind as you travel today.
Persistent Slab: These slabs have been in places where the snow has been stiffed by wind and are failing on buried surface hoar about 1-2’ deep. Most of the activity has been relatively small, but big enough to take someone for an undesirable ride over a cliff or sweep them into a terrain trap. These slabs could be either soft or supportable to the weight a person and will be located on slopes that are more wind loaded. In fact they may resemble a windslab-type look: smooth pillow-shaped and isolated to a specific terrain feature. In the periphery areas of Girdwood, Placer Valley and Johnson Pass more caution is advised due to slightly deeper snow depths, more sustained winds, and the possibility of a larger slab. Identify terrain traps like gullies, cliffs or rocks below before committing to a steep slope.
*Triggering a Deep Persistent Slab is unlikely at this time and has become an outlier. Due to poor structure (basal facets) that can still be found near the ground in the upper reaches of our terrain, 3000’ – 5000’ zone, it is worth keeping in the back of your mind. At this time cold temperatures and benign weather are helping the stability of our snowpack.
Loose Snow: In many places the snow is too loose to form a slab and the surface snow ’sluffs’ away with the weight of a person. Expect loose dry snow to be fast moving in steep terrain and don’t be surprised if it knocks you over as it picks up speed. Manage your ‘sluff’ and be aware of the consequences below you.
Cornices: Cornices are unpredictable and can break further back along a ridge than expected. Give these features plenty of space.
Soft slab triggered remotely on Wednesday along the upper ridge of Eddies. This slab was about 80′ wide and slid into very steep Southwest facing terrain below. Photo by George Creighton
This is an older wind slab on Raggedtop, Girdwood, and is a good example of where a slab could be more supportable due to stronger winds. Photo by Mike Ausman
Loose surface snow and cornices on the Southwest face of Magnum.
Yesterday skies were clear and sunny with a temperature inversion, single digits (F) in valley bottoms and low teens (F) near ridge tops. Ridge top winds averaged around 10 mph with some gusts in the 20’s. No precipitation has occurred in over a week.
Winds are expected to be light from the East (5-15mph) and skies will be clear and sunny. Temperatures look similar to yesterday with slightly warmer ridge top temps, low 20F’s and precipitation is not likely.
A blocking high pressure system over mainland Alaska is expected to persist through the weekend with continued clear skies, cold temperatures and light winds. The long term forecast is calling for similar weather this week with a possibility of a pattern change mid to late week, but a lot of uncertainty still remains.
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin
|Observation: Lynx creek
|Observation: Tincan Trees
|Moderow / Clayton
|Observation: Turnagain (below the uptrack)
|Alaska Avalanche School Moto Level 2
|John Sykes Forecaster
|Observation: Tincan Backdoor, Center Ridge
|AAS Level 1 / R Sullivan
|Avalanche: Tincan Trees
|Schauer/ Moderow/ Stephenson Forecaster
|Schauer/ Moderow/ Clayton Forecaster