Storm snow amounts vary across the region. Avalanche danger at Treeline and Below Treeline may be higher in areas with above average snowfall.
Confidence
Fair - Intensity of incoming weather systems is uncertain on Monday
Weather Forecast
The low pressure system which caused winter storms over the weekend will be replaced by an arctic front on Monday. This arctic front will result in clear, cold, and dry conditions over the interior regions.Monday: Light snowfall in the morning, increasing sun in the afternoon, decreasing temperatures during the day, and moderate to strong alpine winds from the NE as the arctic front approachesTuesday/Wednesday: Mostly sunny, no precipitation, light NE winds, and unseasonably cold conditions.
Avalanche Summary
No recent avalanches have been reported but incoming field data is still very limited.
Snowpack Summary
Variable snowpack depths are being reported across the region but typically 30-50 cm of storm snow has fallen on approximately 1m of old, well-settled snow. The new storm slab will increase in reactivity and destructive potential as it deepens or in areas where it has been redistributed and compressed by wind. The storm slabs are forming over a variety of old snow surfaces including (1) winds slabs and wind scoured areas in the alpine and exposed areas at treeline, (2) sun crusts on steep south facing slopes, and (3) surface hoar in sheltered areas around treeline elevation and below. There are still two layers of concern within the mid/lower snowpack: the early November surface hoar is down roughly half way (50-60cm) and the October rain crust is near the ground. While these layers have recently become dormant, the weight of the new storm snow may cause these layers to reactivate in isolated areas causing large, destructive avalanches. The October crust can be found in the alpine on north aspects (likely east and west as well). The early November surface hoar appears to be spotty and drainage specific.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.