|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.
We received a report of an avalanche on the north side of Tincan Ridge yesterday, running into Todd’s Bowl. It was reported to have been recent and triggered by the winds. We also received a photo of a large slab avalanche on the backside of Seattle Ridge (between Main and Zero Bowls). This slab could be older, but it’s a deeper slab that may have released on the Thanksgiving crust. More on that in our ‘Additional Concerns’ below.
|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
After a break in storms yesterday, another shot for a few inches of snow and wind is slated for today. Plus… an even larger storm is on the horizon for tomorrow into Monday. An active weather pattern is setting up for Southcentral over the next week and with that will come increasing avalanche danger.
For today, ridgetop winds are on the rise from the east (10-20mph with gusts as high as 40mph) and light snowfall should add up to 2-6″ by tonight. With a surface that has already seen varying degrees of wind effect, another round of wind slabs will be adding to the equation. Winds today should be enough that in exposed areas above treeline, and especially along the higher ridgelines, natural wind slab avalanches may occur. These are likely to be in the foot deep category and if they are fresh, should be easy for us to trigger. With low visibility conditions expected, sheltered areas in the mid elevation trees will be the best bet for not only avoiding these avalanches but also finding the softest snow.
As mentioned above, there was a large avalanche seen on the backside of Seattle Ridge on Thursday, 12/7, (photo below) . The slab appears to be 2-3′ deep and has the character of an avalanche releasing on a buried weak layer, as opposed to a typical wind slab for example. This is the first avalanche we have seen that looks like it could have released on the Thanksgiving crust. We do not know when it occurred, but best guesses are sometime in the last week.
Whether this avalanche is a precursor of things to come, we don’t know yet. However, we are keeping a close eye on the buried Thanksgiving crust. We have seen in snow pits that facets are developing on top of the crust. As time goes on these facets can continue to grow and become a weak layer, making the ingredients for a scary avalanche setup: lots of snow on top (big slab), weak layer (facets), over a uniform crust (bed surface).
What we believe is a natural slab avalanche between Main and Zero Bowl on the backside of Seattle Ridge. Thank you to Travis Smith for the photo taken Thursday, 12.07.23.
Yesterday: Partly sunny skies were over the region yesterday after 4-8″ of light snow fell the evening before. Ridgetop winds were from the northwest in the 10-15mph range with gusts near 30mph. Temperatures were cold – single digits.
Today: Clouds have built in overnight and today a weak weather system moves in. Ridgetop winds have turned easterly and should increase through the day to the 15-25mph range with gusts near 40mph in some areas. Between 2-6″ of snow is expected through today before tapering off tonight.
Tomorrow: A more powerful storm is forecast for Sunday into Monday. Strong east winds with 12-18″ of snow could fall by Monday morning. The rain/snow line looks to climb to around 500′ with this event. A stormy weather pattern is setting up for the remainder of the work week.
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′)
|Grouse Creek (700′)
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