Snowfall combined with moderate to strong southwest wind Monday night through Tuesday will increase avalanche danger to HIGH.
A couple of weak layers formed in late November and early December are now sitting about 1 m below the surface. This layer may present as surface hoar, a crust, facets or a combination of those, depending on elevation and aspect.
Snow accumulating above a buried layer of weak surface hoar will create a touchy storm slab problem. The conditions are primed for human triggered avalanches.
MONDAY NIGHT: Snow, accumulation 10-15 cm, moderate to strong southwest wind, alpine high temperature -9 C.
TUESDAY: Flurries, accumulation 10-15 cm, moderate to strong southwest wind, alpine high temperature -4 C.
WEDNESDAY: Flurries, accumulation 5-10 cm, moderate south wind, alpine high temperature -6 C.
THURSDAY: Scattered flurries, moderate southwest winds, alpine high temperature -7 C.
On Saturday there were 3 reports of skier triggered persistent and storm slab avalanches running on surface hoar buried 25-50 cm deep. These ranged from size 1 to 2 and were on north, west and south aspects between 1400 and 2000m. Two of these were remotely triggered (from a distance). There was also a report of a snowmobile triggered size 2 persistent slab avalanche on an east aspect at 2300m
Expect to see an increase in natural avalanche activity as storm snow accumulates through Monday night and Tuesday.
25-40 cm of recent snow has accumulated above a widespread layer of large, feathery surface hoar crystals. New snow is expected to continue to accumulate above this layer over the next few days, making it more sensitive to human-triggering.
A weak layer formed in late November is now buried around 1 m plus below the surface. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect. Below this, a variety of crusts from late October are buried deeper in the snowpack.
