|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.
It was an exciting day in the mountians yesterday with a very touchy snowpack in the elevation band between 2,000 and 3,000′. There were three known large avalanches that occurred (3-5′ deep). Two were triggered at the same time, but on different aspects, from the corniced ridgeline on Tincan (CFR ridge) and one was a natural avalanche on Magnum’s North face near Taylor Pass. You can see many great photos and some write ups on our observation page HERE.
Deep Persistent Slabs:
The primary concern for today are naturally occurring deep slab avalanches that fail in lower layers of the snowpack. These can be up to 5′ thick or more and propagate across entire slopes and terrain features. With a foot of new snow and strong wind overnight adding load to an already unstable snowpack, it’s a simple equation to stay away from avalanche terrain.
There is a mixed bag of weak layers, crusts and interfaces buried anywhere from 2-4+’ deep in our current snowpack. We are unsure what layer was responsible for yesterday’s slides, but the take home point is: There are weak layers/interfaces that have been slowly loaded during the past 2 weeks of storms which are, clearly, still showing signs of reactivity.
Photos below are of the large slab avalanche on Tincan’s CFR bowl, Southwest facing (left photo: Adam Phillips, right photo: Barkley Blair).
Images below are of the skier triggered slides off both the North and South side of Tincan’s CFR ridgeline. To have deep slab avalanches release on two opposite aspects is very unusual and speaks to our currently very complicated snowpack.
Storm snow avalanches associated with just the new snow will be likely but not as large as the deep slab issue mentioned above. Today we can expect wind slabs and storm slabs 1-3′ thick, depending on how much new snow falls. Sluffs should also be expected and could trigger a slab lower on the slope. Cornices will continue to grow and have the ability to fall and trigger large avalanches as well.
Wet Snow Avalanches:
We can also expect wet slab avalanches in the lower elevation band between 1,500′ and 2,500′ due to rising temperatures and a rising rain/snow line today and this afternoon.
Partly cloudy skies yesterday morning quickly gave way to wind and light snowfall by the early afternoon. Heavy snow began falling overnight along with strong Easterly ridgetop winds. There has been around a foot of new snow at Turnagain Pass and Girdwood Valley with a rain/snow line ~500. Winds have been wreaking havoc at hourly averages in the 60’s and gusts to 107mph. See the charts below for additional 24-hour data.
Today we can expect a short break in precipitation before another 10-14″ of new snow is forecast to fall later today (~1″ water equivalent) with a rain/snow line rising to possibly 1,500′, and even higher. The gale force ridgetop winds are expected to continue from the East, averaging in the 50-60mph range. Temperatures look to rise to the upper 20’s and possibly 30F on the ridgelines and the upper 30’s at 1.000′.
The pulse of precipitation that moves in later today should remain through tomorrow with periods of heavy snowfall and rain to 1,500′. Monday we could see a break in weather before another round of rain, snow and wind early this coming week.
|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: 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
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin
|Observation: Lynx creek