|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
With another day of quiet weather today, we are not expecting to see any big differences in the big picture stability-wise. The layer of weak faceted snow that was buried back in mid-November is still lurking below the surface, and it is possible a person could trigger a very large avalanche if they find the wrong spot on or below a slope. This layer is buried 3-5′ deep in the northern half of the advisory area, 2-3′ deep towards the southern end of Turnagain Pass and towards Johnson Pass, and 1.5-2′ deep in the Summit Lake area. The most likely place to trigger one of these monsters will be in areas with a shallower snowpack, so the likelihood of triggering an avalanche increases as you travel further south. That said, the entire advisory area (and surrounding periphery zones) appear to share the same poor structure, and you really can’t rule out a very large human-triggered avalanche given that untrustworthy setup.
As we have mentioned before, there are a few things that make deep slabs a tricky problem to deal with. They will rarely give you warning signs like shooting cracks or collapsing, or poor stability test results, even though the snowpack is capable of producing a large avalanche. They may be triggered remotely from above, below, or to the side of a slope. They can also propagate very wide, connecting multiple terrain features that may otherwise seem like they could interrupt avalanche paths (revisit the avalanche from 12/2 on Eddie’s for an example of this). Given the lack of feedback and the high consequences of being caught in a deep slab avalanche, the only way to manage this problem is to stick with the status quo of avoiding spending time on or below steep slopes for now.
Wind Slabs: There may be some isolated wind slabs that formed earlier in the week on top of a new layer of weak snow that could remain reactive today. A relatively small avalanche triggered near the surface has the potential to step down to deeper weak layers, creating a larger avalanche. Be on the lookout for lingering wind slabs near ridgelines, gullies, and convexities in the mid and upper elevations. Look for clear warning signs like shooting cracks or collapsing, and be suspect of slopes with stiff or punchy snow on the surface.
Glide Avalanches: We saw one glide avalanche release in the past week, and there were some glide cracks that look like they had been creeping recently up Lynx Creek. Glide avalanches are destructive and unpredictable, so as always, limit your time spent traveling below glide cracks.
Glide avalanche in the Lynx Creek drainage from 12/16 or 12/17, which triggered a slab avalanche on the Halloween facets on its way down. 12.18.2021
Video with a snowpack summary from Lynx Creek yesterday (12/18). Linked here.
Yesterday: Skies were mostly cloudy in the morning, gradually breaking up with improving visibility and pockets of sun in the afternoon. Winds were light out of the west at around 5-10 mph, with gusts in the 20’s and up above 30 mph in Summit. High temperatures were in the low 20’s F at ridgetops, and in the upper 20’s F at mid and lower elevations. Some areas saw a trace of snow.
Today: Another day of quiet weather is expected today, with highs in the upper teens to low 20’s F and light westerly winds blowing around 5 mph. Skies will be mostly cloudy, with chances for some sun especially towards Summit Lakes and Seward. No precipitation is expected today.
Tomorrow: We should see some more active weather starting to pick up tomorrow. High temperatures are expected in the low to mid 20’s F, with increasing cloud cover during the day. Chances for snow pick up Monday night, with 2-4″ possible by Tuesday morning. Expect to see a bump in winds as an outflow event follows on the heels of this brief pulse late Monday night and Tuesday morning.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
RIDGETOP 24-hour data (6am – 6am)
|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