Avoid wind loaded features on all aspects, winds are expected to vary. Steer clear of sun affected slopes if skies clear, even short bursts of sunshine may increase reactivity.
Deep persistent weak layers continue to be a concern in this region. Read about managing this problem in our latest Forecasters' Blog.
Recent storm snow has been affected by southwest winds, which switch to southeast on Saturday. Expect deeper wind affected deposits on many slopes, while sheltered terrain produce loose dry avalanches - be prepared to manage your sluff.
Additionally areas that see clear skies and strong sun should avoid sun affected slopes. Surface snow may rapidly lose cohesion.
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's deep burial depth, but smaller avalanches in motion have the potential to step down. Suspect terrain for human triggering includes steep, thin, shallow, and rocky terrain.
On Thursday storm slabs were reported human triggered to size 1. Natural avalanches were reported to size 2.5 thought to occur during heavy snowfall or wind loading. Operators reported rapid loading due to winds at higher elevations but observations were limited due to visibility and weather. We expect a natural cycle to have occurred, especially in wind loaded features and that human triggered avalanches were also likely.
A few very large (size 3.5 to 4) deep persistent slab avalanches were also observed over last week, which likely occurred during the very windy arctic outflow event.
Storm totals have reached 30-80 cm. Variable winds have redistributed this into deeper deposits on many aspects. This storm snow sits over wind effected surfaces, a thin sun crust on steep south facing slopes.
Below this interface, around 50-90 cm deep, a layer of small surface hoar from exists in lower elevation sheltered areas and more widespread faceted (sugary) snow and heavy wind effect from the late February Arctic blast. Reports suggest this interface is beginning to bond and strengthen.
The remainder of the mid-snowpack is considered generally strong with a small surface hoar layer buried over 1 m deep from mid February. Reports suggest this layer is bonding well but most likely found around treeline elevations in areas sheltered from the wind.
Large and weak facets that formed in November are found near the base of the snowpack. Although the likelihood of triggering this layer is low at this time, the consequence of doing so remains very high. This layer is most likely to be human-triggered in thin, rocky slopes at alpine and upper treeline elevations.
Friday Night
Cloudy with easing flurries. Light southwest winds. Freezing levels below valley bottom.
Saturday
A mix of sun and cloud. Light to moderate easterly winds. Freezing levels below valley bottom, alpine high of -6 °C.
Sunday
A mix of sun and cloud. Light to moderate east winds. Freezing levels below valley bottom, alpine high of -8 °C. Possible flurries.
Monday
Mostly cloudy. Moderate southerly winds. Freezing levels below valley bottom, alpine high of -5 °C. Flurries possible.
More details can be found in the Mountain Weather Forecast.
