Avalanche Forecast

We’ve received 37” of snow with over 4.3” of water equivalent on Stevens Pass during the week. The first 9 days in December were clear and cold. Surface hoar grew large during this time, and facets developed near the surface of the cold, low density snow. On December 9th this layer was covered up and preserved on many aspects and elevations. December 11th was the last natural avalanche cycle we know of in this zone. On this day, professional observers reported natural, and remotely triggered avalanches within the storm snow and on the December 9th layer. These were on a variety of aspects and as low as 4700ft. On December 12th and 13th observers reported whumphing and collapses near ridgelines. Currently, this layer is three feet down and snowpack tests are indicating that if triggered, it will likely propagate.

Check out this video that helps demonstrate the problem here with Part 1  and Part 2

Winter is here.

A productive winter storm pattern has elevated the avalanche danger and provided an interesting start to the season.  

A quick breakdown:

• Tuesday and Wednesday saw a significant localized avalanche cycles.

• We have a lot of new snow...2’ to 5’ above 4500ft.

• We’ve gotten a lot of wind.

• We have weak layers near the ground.

Dangerous avalanche conditions will persist over the next couple of days. That said, it is early season and the flavor of avalanche you may run into is likely a function of elevation, timing, and dumb luck.

Here are some basic emerging patterns:

• Snowfall totals so far this week (Monday morning to Thursday evening) illustrate more recent snowfall in the north than the south:

  • Mt. Baker: 55”

  • Washington Pass: 29”

  • Stevens Pass: 37”

  • Snoqualmie Pass: 28”

  • Paradise: 38”

  • Mt. Hood Meadows: 13”

• Upper versus Lower Elevations: The change in the snowpack is still pretty dramatic with elevation. Height of snow decreases rapidly below 4500’ at Baker and Washington Pass, 5500’ at Crystal/Rainier. The Passes have better low elevation coverage, but it's still pretty thin below 4000’. With additional warm storms in the forecast, this pattern is expected to continue for awhile.

• East versus West: Loading along the East slope has been more incremental, and a  variety of buried facet and surface hoar layers may be found. This is most pronounced near WA Pass. Although significant snowfalls and precip totals have resulted in thicker, more homogeneous snowpack in the western zones, lingering weak layers near the ground will persist through the week.

The uncertainty of how reactive our buried weak layers are will carry into the weekend. Be cautious and get home safe.