Avalanche conditions remain very dangerous with warm temperatures, recent new snow that formed a dense storm slab and a persistent weak layer in the snowpack.
Cornices are reactive to human traffic with the warm temperatures and natural cornice falls become more likely. Large cornice falls are dangerous on their own.
A failed cornice can trigger buried persistent weak layers and result in very large and destructive avalanches.
A persistent slab problem formed by a crust down 100-270 cm has created a low likelihood, high consequence scenario that is difficult to forecast. There has been an increase of avalanche reports on this layer recently. It is uncertain how the forecast warm temperatures will affect the snowpack and if we will see more activity on this layer during the warm period.
Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack. Large additional loads like small avalanches or cornice falls can trigger deeper weak layers. The same feature or path can slide repeatedly when the persistent weak layer is reloaded with new snow.
Up to 35 cm new snow fell with warm temperatures building a dense storm slab. Expect to find more reactive deposits around ridge features. Be especially mindful around steep and convex openings in the trees.
The new and recent storm snow may overlie a weak interface which could result in deeper and touchier than expected slabs. Smaller avalanches can step down and trigger deeper weak layers resulting in large and destructive avalanches.
Wednesday night: Cloudy, up to 5 cm new snow, moderate southwest wind, treeline low around -1 °C, freezing level around 2000 m.
Thursday: Mostly sunny, moderate southwest wind, treeline high around +2 °C, freezing level around 2000 m.
Friday: Mix of sun and cloud, up to 3 cm new snow, light westerly wind, treeline high around -2 °C, freezing level around 1200 m.
Saturday: Mostly cloudy, up to 3 cm new snow, moderate southwest wind, treeline high around -2 °C, freezing level around 1400 m.
On Monday and Tuesday, now new avalanches were reported.
On Sunday, a few natural cornice failures resulting in size 2.5 avalanches were observed as well as a natural size 2 slab avalanche.
On Saturday, storm slab avalanches up to size 2.5 were triggered by explosives. Overnight, a large (size 3.5) natural storm slab avalanche released and a large (size 2.5) cornice failure occurred.
The persistent slab problem has produced sporadic and spotty activity in the Lizard-Flathead and nearby regions.
The storm brought up to 35 cm of dense, new snow. The new snow sits on soft snow in sheltered areas, wind slabs in exposed and open areas which formed over the past few days. The previous storm snow totalled 40-50 cm and covered a soft, faceted snow surface which formed during cold temperatures. This layer may still take a little time to bond.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 100-270 cm. Activity on this layer has been sporadic, the most recent persistent slab avalanche in the region was reported on January 9. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
