As the storm subsides, the snowpack will need some time to regain strength.
Make conservative decisions for the time being.
Precipitation amounts will begin to taper off later today. Warm temperatures will have this fall as rain at lower elevations and as heavy wet snow at higher elevations.
Whether it is rain, heavy snow, or a large wind deposit of snow, avalanche activity is expected to increase.
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth.
Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
Sunday saw an increase in avalanche activity as this most recent weather system touched down in our region. The primary cause of these avalanches were wind slabs and storm slabs with a couple of persistent slabs as well.
This persistent slab avalanche occurred on buried surface hoar down 30 cm. It was accidentally triggered on an east face and reached size 1.5.
With regard to the wind slabs, it is notable that several of these avalanches occurred on the western aspects and they slid easily on a solar crust that was formed early last week. One of these wind slab avalanches was accidentally triggered remotely in the alpine on a northeast aspect. The resulting size two avalanche which was 30 cm deep, ran 50 m. It carried one of the party members 40 m. They stayed on top of the avalanche but sustained a leg injury and had to be helicoptered out of the area.
By Tuesday morning the highest elevations of our region will have storm snow totals reaching over 30 cm. Due to recent high freezing levels much of this fell as moist heavy snow or rain. Expect wind slabs to have formed from southwest winds where snow was light enough to be transported.
On southerly aspects and below treeline, there is a widespread cust buried 30 to 50 cm down. On north-facing slopes at treeline and above there may exist a layer of faceted snow or surface hoar in shelter areas. Further down in the snowpack, around 60 cm, a surface hoar layer may exist.
The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Monday Night
Cloudy, 5 to 15 cm accumulation, winds southwest 15 to 25 km/h, freezing levels getting down to 1000 m.
Tuesday
Cloudy with potential late day clear periods, 5 to 10 cm accumulation, winds southwest 25 km/h, freezing levels to 1500 m.
Wednesday
Cloudy with sunny periods, 5 to 10 cm accumulation and 2 cm throughout the day, winds westerly 15 km/h, freezing level starting at 500 and climbing back up to 1500 m.
Thursday
Cloudy with sunny periods, trace accumulation, winds westerly 10 to 15 km/h, freezing levels starting at the valley bottom and climbing to 1600 m.
More details can be found in the Mountain Weather Forecast.
