We will be providing an AIARE Avalanche Level 1 Class this winter in Haines, February 23-25, 2018
Above 2,500ft Considerable
1,500 to 2,500ft Considerable
Below 1,500ft Considerable
Degrees of Avalanche Danger ?
Problem #1: Storm Snow
6-12″ of new snow fell Tuesday-Thursday in this zone, with a strong warming trend. South winds were strong for several hours, heavily loading North-ish aspects. All this heavy, moist new snow is sitting atop cold, weak low-density fluff from a few days ago. There is a lot of settling going on right now as the older snow layers compress. There are still several new and recent storm interfaces that will be unstable today. Human triggered avalanches are likely on slopes steeper than 30 degrees, especially areas with recent wind loading.
Problem #2: Persistent Slab
Beneath the recent wind slabs that built over the last week or two, we have a layer of weak facetted snow sitting above an ice crust. This failure plane, about 30-80cm deep, may re-activate given the heavy new load of snow. Smaller avalanches may step-down to this layer as well. Any failures this deep will propagate widely with high consequences. In addition, a layer of depth hoar at the ground may also collapse and cause large, deep avalanches.
Recent Avalanche Activity
October 28th: First rider-triggered slide reported from the peak north of Nadahini (“Sunny Bunny”). D2 soft slab ran in storm snow from Oct 26-27. Nobody caught or injured. [ SS-AR-D2-R3-S ] South aspect @ 6,200ft.
Small – Moderate natural avalanche activity is occurring during/after storms. So far it has been mostly loose-snow slides, with a few slab avalanches as well.
Friday-Saturday should be mostly clear with light winds. Some clouds/light snow is possible Saturday afternoon/evening. A strong wet storm is likely for Sunday.
|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
|32″||9″ / 0.80||17″ / 1.35||0||light, var||0″ / 0.00 *|
Flower Mountain @ treeline
|26″||6″ / 0.40||15″ / 1.00||0||light, var||0″ / 0.00 *|
Chilkat Pass @ 3,500ft
|18″ *||6″ / 0.40 *||9″ / 0.70 *||0||light, var||0″ / 0.00 *|
( *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 45-100cm 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. This will be a weak base to hold up future heavy snows. Keep this in mind as November progresses and snow depths increase. This will likely turn into a deep-persistent slab problem.
Start the season with fresh batteries in your beacon, and practice with your beacon, shovel, and probe.
If you get out on the snow, send in your observations!