Above 2,500ft Moderate
1,500 to 2,500ft Low
Below 1,500ft Low
Degrees of Avalanche Danger ?
Problem #1: Wind Slab
While the midpack is mostly dense and well bonded, the top of the snowpack contains recent wind slabs from the last storm or wind events just after. These slabs are still moving around on slopes steeper than 30 degrees. In some wind-loaded areas, these wind slabs may be 30+cm thick. Variability is high right now, and some slopes are much sketchier than others. Listen for a hollow-sounding snowpack, probe around with your poles for hard-over-soft layering, and utilize test slopes and pits to assess this danger on each slope. Careful terrain management will help mitigate this danger. If you find slabby snow on steep terrain, play it safe and just say no.
Problem #2: Deep Slab
We still have 2-4mm depth hoar at the ground, beneath a hard midpack. During the last storm several slides ran on this layer as a heavy load of new precipitation placed strain on it. Now that things have settled down, triggering this deep layer will be difficult, but still possible. This is especially true in thin/rocky areas which will act as trigger points, and may cause remote triggering and wide propagation. The best way to manage this danger is to stick to areas with a deeper snowpack, make sure your safe areas are well-outside the danger zone, and include a wide safety margin. Careful group management is crucial right now, as any slides that break this deep could be large, and break wider than expected.
Recent Avalanche Activity
Recent natural avalanche activity from several days ago includes:
- Isolated D1-D2 wind slabs at the top of the snowpack, on steep slopes above treeline, all aspects.
- Isolated full-depth D2-D3 hard slabs that came down during last week’s wet, wild weather. On steep slopes above treeline, all aspects.
Cold and dry weather will persist for several days. We may finish out December without any more snow.
|Snow Depth [in]||Last 24-hr Snow/SWE [in]||Last 3-days Snow/SWE [in]||Today’s Freezing Level [ft]||Today’s Winds||Next 24-hr Snow/SWE|
Mount Ripinsky @ treeline
|18″||0″ / 0.00||0″ / 0.00||0||mod, N||0″/ 0.00 *|
Flower Mountain @ treeline
|24″||0″ / 0.00||0″ / 0.00||0||light, NW||0″ / 0.00 *|
Chilkat Pass @ 3,500ft
|12″||0″ / 0.00 *||0″ / 0.00 *||0||light, NW||0″ / 0.0 *|
( *star means meteorological estimate )
Additional Info & Media
A few notes:
- We had an extremely dry, cold early-season. Total precipitation October 1st – November 28th was around 30% of normal. Snow depths are between 45-130cm in most areas. Variability is high due to persistent dry, windy conditions.
- Temperatures hovered around 0 – 15°F for almost all of November. This has caused faceting of the thin snowpack and built up 3-5mm depth hoar at the ground in all zones.
If you get out on the snow, send in your observations!
We will be providing an AIARE Avalanche Level 1 Class this winter in Haines, February 23-25, 2018