Storm slabs building on top of the low density snow that fell early in the week will remain reactive through the weekend.
A lingering weakness deep in the snowpack mean that storm slabs could step down and produce larger than expected avalanches. Minimizing overhead exposure and ensuring you do not ski cut slopes above other parties, are both good ways of managing this risk.
Low density storm snow, moderate/strong ridge-top winds, and rising freezing levels are creating slabs in the upper snowpack. Watch for signs of reactivity such as shooting cracks and recent avalanches.
Last week, a large cornice-triggered avalanche stepped down to this basal layer near Grizzly Peak. Watch for steep, thin rocky areas where this layer could be activated.
On Friday we received a report of a natural size 2.0 slab avalanche from the South face of Bruins peak.
On Thursday there were reports of a size 2 avalanche from Frequent Flyer and a size 1.5 from Cheops North #4.
Wednesday-Thursday there was a natural cycle in steep terrain in the highway corridor of loose snow and slab avalanches failing in the recent storm snow. Avalanches were mostly size 1.5-2, with isolated size 2.5-3.
A natural cornice failure triggered a size 3 deep persistent slab on the SE slope of Grizzly Peak on Saturday.
Snowfall and strong winds will continue to build storm slabs overnight. The 40-60cm of recently accumulated snow sits on a firm surface of old wind-effect in the alpine/treeline and a melt freeze crust below treeline.
The early Jan surface hoar layers are buried 60-90cm and were most prevalent at treeline. The November 17th weakness can still be found near the base of the snowpack in many areas - this layer is mainly facets, with a crust and/or old surface hoar in some locations.
The next "storm" arrives tonight into Saturday, bringing steady flurries and strong alpine winds.
Tonight: Snow (5-10cm). Alpine low -8*C. Moderate, gusting strong, SW ridgetop winds.
Saturday: Flurries (~5 cm), Alp High -5*C, Freezing level 1300 m. Moderate SW winds.
Sunday: Cloudy with scattered flurries. Low -9 °C, High -5 °C. Light SW wind.
Monday: Cloudy with scattered flurries. Low -12 °C, High -7 °C. Light West wind.
