Strong wind and new snow may form reactive wind slabs on Friday.
Be mindful of the lingering deep persistent slab problem. Forecast warming temperatures and sunshine this weekend may be enough to wake this problem up and initiate large and destructive avalanches.
5-20 cm of snow accompanied by strong winds and warmer temperatures have formed reactive wind slabs. They will likely be touchier on leeward slopes with deeper, wind-loaded conditions, especially where they sit on surface hoar or crusts.
A hit of sunshine Friday may trigger loose-dry sloughing from steeper terrain features.
A deep persistent slab problem formed by a crust exists down 140-200 cm in the snowpack. Currently, a lot of uncertainty exists around this layer as its been dormant for a little while now and is considered a low probability-high consequence avalanche problem.
However, change is in the air and it's going to get WARM this weekend. The warming and sunshine may be enough to wake this layer up and initiate large to very large and destructive avalanches. Smaller avalanches may step-down and trigger this layer.
Friday: Mix of sun and cloud. Ridgetop wind gusty up to 40 km/hr from the West/ Northwest. Alpine temperatures -4 and freezing levels 1200 m.
Saturday: Mix of sun and cloud. Mostly valley cloud due to a temperature inversion. Alpine temperatures near +2 with freezing levels 1000 m. Ridgetop wind will be moderate from the northwest.
Sunday: Similar to Saturday with continued warm air aloft bringing alpine temperatures to +3 and freezing levels 1200 m. Ridgetop wind moderate to strong from the West.
On Thursday, numerous storm slab avalanches were reported up to size 2.
Wind slabs will likely be the name of the game on Friday with forecast strong winds redistributing the new snow on leeward slopes.
During the warm previous storm, mid-last week, a large widespread avalanche cycle occurred with most avalanches releasing within the storm snow and some on Jan 11 surface hoar layer. Strong solar radiation and warm temperatures were also at play after the storm, producing numerous avalanches at all elevations and scouring avalanche paths to the ground in places.
The December crust/ facet interface has been dormant for a while. Although the activity on this layer has tapered off, it still remains a concern especially moving into the weekend with warming and sunshine. We are concerned that this layer may wake up again.
10-20 cm of new snow fell by Thursday afternoon. Just enough to freshen things up and bury a series of recent surface hoar layers and melt-freeze crusts found down 15 cm and another down 25 cm. These extend to 2400 m and are most prevalent (thicker) on southerly aspects.
Digging deeper, down 50-60 cm is yet another surface hoar layer that has seen recent avalanche activity. A well-consolidated mid-pack exists below this and above the early December crust/facet interface.
The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past month. The crust is now buried 120-200 cm deep except in thin, wind-affected areas near ridgetops. Warming and smaller avalanches through the forecast period may be enough to wake this layer up and iniate large to very large avalanches.
