|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.
The last known human-triggerd avalanche reported was a small wind slab pocket on Tincan, on Friday (12/1). Beyond that, observers have been reporting evidence of a natural avalanche cycle that likely ramped up as last week’s storm was winding down last Thursday (11/30). Crowns were reported from Main bowl and Warm up bowl on the moto side of the highway to Sunburst and upper Bertha Creek on the non moto side.
|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 ample snow available for transport in the wake of our late November storm last week, it doesn’t take very strong winds to build touchy wind slabs. Winds were primarily from the East/ Northeast yesterday and stronger at higher elevations. We can expect a slight wind shift today to a more West/ Northwest direction. Ridgelines, steep gullies and convex rollovers should be approached with caution and with the expectation that you may trigger a wind slab. Based on new snow yesterday/ overnight and snow available for transport, wind slabs are likely to be in the 6-18″ deep range.
Keep eyes and ears out for surface conditions changing under your skis or snowmachine. If the surface all of the sudden feels stiff or drum-like, you are likely flirting with a wind slab. Shooting cracks or whumpfing are obvious signs of instability but may not present before an avalanche. Small, non-consequential test slopes are also a good way to suss out just how reactive this avalanche problem may be today. Another good option could be simply to seek out protected terrain in the trees where winds have had less effect on the snow surface. We found really good, dry snow with minimal wind effect yesterday in ~1,500-2,500 elevation band in Lynx Creek. Bonus: visibility was waaaay better in the trees!
Currently, the Summit Lake zone has a similar snowpack setup as the Turnagain area and was seeing active wind loading yesterday. More info on current conditions here.
This is what active wind loading looks like courtesy of the Sunburst webcam at 3,800′. Image taken at 6:30p last night.
Forecasters and observers have found the Thanksgiving crust to be widespread throughout the forecast area. The good news is that literally thousands of slope testers over the past four days since it was buried have put countless tracks on all aspects and elevations throughout the advisory area with minimal avalanches on this layer. Snowpit test results have been mixed, with some pits showing the potential to propagate a crack and others showing no concern. The bad news is that crusts are notorious for ‘waking back up’ down the road as the snow weakens and facets out above and below these layers.
It’s quite easy right now to dig down into the mid-snowpack to get yourself acquainted with this usual suspect unaffectionately referred to as the “Thanksgiving Crust”. We’ll continue to keep tabs on this layer as the season progresses. And for you daily readers, this certainly won’t be the last you hear of the TC.
Snow grains pulled from the layer directly above the Thanksgiving crust. No obvious faceted grains in either of our pits yesterday but we’ll be keeping close tabs on this layer in the days and weeks ahead. 12.04.2023
We’re also still paying attention to the layer of facets at the ground in the highest elevations (above around 3500-4000′). This layer is now buried 6-8′ deep in that upper elevation band, so you’d need to find the perfect thin spot to trigger an avalanche on it. That said, if someone were to trigger an avalanche on this layer it would be huge. The layer seems to be very isolated, but the most problematic terrain will be high elevation, steep, rocky slopes with a thinner overall depth.
Yesterday: Skies were mostly obscured with moderate to light snow falling throughout the day and into the evening hours. Temperatures were in the mid to high 20’s throughout the day with winds in the teens and gusting into the 30’s from the NE at ridgetops. Total snow accumulation was 2-3″.
Today: It looks to be another grey-bird day on tap. We can expect mostly cloudy skies, another 1-3″ of snow with a slight wind shift to the Northwest. Winds will be in the teens and gusting to 20s mph at ridgetop locations. Temps will start out in the mid to high 20’s at 1,000′ and drop to the low 20’s throughout the day.
Tomorrow: Temps will continue to slide a bit as colder air fills in behind the current low pressure that is tracking north. We can expect our moderate winds to continue from the North and West with a chance for a few more inches of snow. Temps look cold enough to support snow at sea level!
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Bear Valley – Portage (132′)
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
|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
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin
|Observation: Lynx creek
|Observation: Tincan Trees
|Moderow / Clayton