|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.
Yesterday a westerly flow moved over area in the early afternoon and winds increased into the 20s gusting into the 40s. This continued through the evening. The way this wind direction shows up in terrain can cause unusual loading patterns. The winds blew from the South on the Sunburst/Tincan side of the road loading N slopes. On Seattle Ridge the winds were from the W/NW and loaded more easterly slopes. These patterns were varied around Girdwood, Portage and Summit Lake as well. There was a few inches of light fluffy new snow that was easily moved as well as soft settling snow from the Xmas storm. Expect fresh wind slab in leeward areas. Look for cracking and pillowed snow. These may be quite tender and reactive. The winds also had the potential to stiffen the slab sitting over older weak layers, add load to the snowpack and make it possible to trigger a deeper avalanche.
Wind on Sunburst yesterday.
Many people have been out enjoying the recent snow with no incident and for the most part avoiding steep slopes. There have been no reported human triggered avalanches since Monday and the natural avalanche cycle associated with the storm also ended that day. As visibility has improved is easy to see the remnants of this cycle. Many areas have had large slides that we suspect ran on the December 24th surface hoar, the December 15th layer of surface hoar or buried facets deeper in the pack. In addition there was a number of mid-elevation band slides that also ran on buried weak layers, some even running on facets just above the ground. The slides at all elevations are mostly 2-4′ thick. There are areas adjacent to those that slid that may still have the potential to go today. It is important to remember thinner areas are often the place that old weak layers are initiated. The snowpack is still complex and it may be harder to initiate but the slides could still be large and deadly. Observers yesterday still reported large whumpfs and shooting cracks. These are red flags and a good indication to stay away from avalanche terrain if encountered. As you choose terrain to ride or ski today think about how large and connected it might be. It may not be the 1st snowmachine rider or skier onto the slope that triggers it. Triggering a deep persistent slab is possible and winds from yesterday may have added stress/load.
Slide on North side of Magnum believed to have run Monday December 26th. Photo: Andy Moderow
The December 24th layer of buried surface hoar visible in the snowpack on Sunburst and still reactive in instability tests.
Expect cornices to be sensitive and easy to break off. They also could trigger a slab avalanche below. Be extra cautious near ridgelines today where cornices can be challenging to navigate. If you suspect a corniced ridge give these a wide berth and be aware of people below you. Due to the unsusal wind loading yesterday look for new cornices or unsual loading patterns.
Sunburst Cornice 12.28.16
Yesterday was mostly cloudy with a few light snowflakes falling. Winds were WNW and increased in the afternoon gusting into the 40s.Temperatures were in the low 20Fs and teens. Temperatures dropped to single digits overnight.
Today will mostly cloudy with the snow starting in the late afternoon. Temperatures will rise again into the 20s. Overnight the temperatures at lower elevations may rise into the low 30s and a rain/snow mix is expected with the storm system as it moves into the area. 2-6″ of snow is possible overnight. Winds will be light and Southerly.
Tomorrow snow showers will continue and temperatures will drop back into the low 20s. Winds will be variable as the system passes through. The pattern continues to be unsettled into next week as a series of fronts move off of the Pacific.
|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′)
|Observation: Silvertip Creek
|Observation: Seattle Ridge
|John Sykes Forecaster
|Observation: Kickstep NE Bowl
|Observation: TinCan Backdoor/ Center Ridge
|AAS L1 Turnagain
|Avalanche: Lynx Creek
|Observation: Turnagain, Seattle, Mt Ascension
|Silverton Mountain Guides
|Observation: Tincan Trees
|Dalpes/Thamm/ Schauer Forecaster
|Observation: Seward Highway across from Johnson Pass TH