Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Regions
Lizard-Flathead.
I'm expecting some overnight snow that is likely to get blown into fresh wind slabs in exposed areas.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
SATURDAY NIGHT: 15-20 cm additional new snow expected. Strong southwesterly winds.SUNDAY: Mostly light snow with the occasionaly heavier flurry. 2-5 cm. Light or moderate northwesterly winds. Treeline temperatures around -4C.MONDAY: Dry with sunny breaks. Light northerly winds. Treeline temperatures around -12C.TUESDAY: Dry with sunny breaks. Light southwesterly winds. Treeline temperatures around -12C.
Avalanche Summary
Small (size 1.5) storm slabs were reported in response to skier traffic on Saturday.A great MIN report from Corbin on Thursday identifies a few slabs initiating in thin, rocky areas on a south aspect. Check out the report here.
Snowpack Summary
Saturday's storm added approximately 20 cm new snow, accompanied by strong southeasterly winds. In total, 80-130 cm of snowfall through December has formed a slab that sits on a persistent weak layer that formed in early December. This layer mostly consists of facets (sugary snow) with some isolated areas also containing small surface hoar (feathery crystals). All this overlies several other weak layers observed in the lower snowpack such as crusts and facets that formed in late October/early November. With this weak basal snowpack, it is possible that an avalanche triggered on the persistent slab would step down to these lower layers, resulting in a full depth avalanche.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.