Hazard will improve as precipitation stops and freezing levels lower throughout the day.
The storm brought a mix of rain and snow to higher elevations. As you transition into dry snow and wind-blown areas watch for cohesive storm slabs that are reactive to human triggering.
This week's storm brought 20 - 30 mm of precipitation as a mix of rain and snow to higher elevations. Where snow remained dry it has formed reactive storm slabs that may remain reactive to human triggering.
Closely monitor how new snow is bonding to the underlying surfaces. Be aware that slab avalanches could step down to deeper layers producing larger-than-expected avalanches.
There are two layers of concern leaving professionals with uncertainty in the region. The first is a crust found down 40 -70 cm that has slowly been healing however in isolated areas weak crystals may surround this layer.
Secondly, the lower snowpack is made up of facets and depth hoar. The new load and prolonged warm temperatures may trigger deep layers resulting in very large avalanches.
Give the snowpack a few days to settle with the new load before discounting deep persistent weak layers. Avoid thick-to-thin areas where triggering deep weak layers is more likely.
On Thursday, several natural loose wet avalanches, up to size 1, were observed below treeline. Several explosive-triggered, size 1.5 storm slab avalanches were reported.
Please continue to post your observations and photos to the Mountain Information Network. It helps strengthen our data gathering.
15-30 cm of new snow and strong southerly winds have built storm slabs in lees. New snow overlies previous wind-affected surfaces and possibly a sun melt-freeze crust on steep solar slopes.
In sheltered terrain, 40 to 70 cm of low-density snow sits over a crust formed in late December. This crust varies in thickness throughout the terrain and elevation. Uncertainty remains about the robustness of this crust above 2100 m. Storm slab avalanches could potentially step down to this layer, creating larger-than-expected avalanches.
There is a widespread layer of facets and depth hoar at the bottom of the snowpack. Uncertainty remains around the likelihood of triggering this layer. Snowpack depths around treeline are about 150 cm deep. The snowpack below treeline is very shallow and faceted.
Friday Night
Periods of snow continue, 5-10 mm. Winds will ease to southerly 40 km/h. Ridgetop low-temperature -1 C. Freezing levels will slowly fall to near 1500 m by Saturday morning.
Saturday
Cloudy with sunny periods and isolated flurries, trace accumulation. Southeast winds of 40 to 60 km/h. Ridgetop high-temperature -1 C. Freezing levels will be near 1500 m.
Sunday
Cloudy with sunny periods and isolated flurries, trace accumulation. Light variable winds gusting 20 km/h. Ridgetop high-temperature -1 C. Freezing levels 1200 m.
Monday
Cloudy with sunny periods and isolated flurries, 5 mm. Light variable winds gusting 20 km/h. Ridgetop high-temperature -3 C. Freezing levels 1000 m.
More details can be found in the Mountain Weather Forecast.
