|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 storm snow by itself didn’t seem to be creating very reactive or connected avalanches yesterday. Adding wind loading to the mix built the stiffness and tension required to build a slab. Wind loaded areas steeper than 35 degrees should be approached with caution today. Any areas with this combination in high consequence terrain should be avoided completely. Check out the observations from yesterday for some more examples of skier triggered wind slabs.
Likelihood – human triggered likely
Trend – decreasing since yesterday
Distribution – Widespread above treeline
Size – small to medium
Below treeline where wind did not affect the new snow, the snowpack behaves differently. We found very little difference in density between the fresh light powder and the underlying weak facets. However, I wouldn’t rule out the possibility of finding unstable storm snow below treeline. If you find the right combination of an open steep slope at lower elevation, it may be able to avalanche as a slab or as a loose sluff. This should be less dangerous than the wind slabs found up higher.
The storm Saturday to Sunday morning dropped about 10 inches across Turnagain Pass. Winds were strong from the east, reaching gusts over 70mph.
Today looks like calm weather that won’t contribute to avalanche problems. A chance of snow is in the forecast with little accumulation. Light wind and mild below freezing temperatures in the mountains. The next chance of significant snow looks to be Wednesday.
This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).
Wendy will issue the next advisory Tuesday morning, December 11th.
|Observation: Silvertip Creek
|Observation: Seattle Ridge
|John Sykes Forecaster
|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