Overnight snowfall and wind will keep storm slabs fresh Friday. In areas that receive less than 10 cm of new snow, avalanche danger may be a step lower.
30-80 cm sits on a buried weak layer that consists of facets, surface hoar, or a crust, depending on location. Avalanches on this layer may propagate widely.
Storm slabs will likely continue to be reactive, especially in wind loaded areas and in places that see more than 15 cm of new snow overnight.
Thursday night: Snow, 5-10 cm for most areas with a possibility of locally enhanced snowfall amounts as high as 20 cm near Hope and 30 cm along the southern border of the region. Moderate to strong westerly ridgetop wind, alpine temperature near -7.
Friday: Mainly cloudy with a few flurries, moderate northwest ridgetop wind, alpine high -4, freezing level rising to 1200 m.
Saturday: Mostly cloudy with flurries, moderate westerly ridgetop wind, alpine high -8, freezing level 800 m in the north, 1300 m in the south.
Sunday: Mix of sun and cloud, light variable wind, alpine high -10, freezing level valley bottom.
In the clear weather on Wednesday, evidence of a widespread natural storm slab avalanche cycle up to size 2 was observed. It is suspected to have occurred during the storm on Monday night. Since this event, there have been reports of natural, explosive and human triggered avalanches size 1-1.5. Many of these failed on the recently buried persistent weak layer.
Overnight snowfall with moderate to strong northwest winds will likely form reactive slabs in the alpine and open treeline areas. The south of the region may see enhanced snowfall amounts as high as 30 cm.
30-80 cm of recent snow sits on a persistent weak layer that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1600 m, and a sun crust on south-facing slopes.
In the south, the underlying snowpack is well consolidated. In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports suggest that this layer is gaining strength and it has been unreactive in recent weeks.
