Slabs have been reactive to human traffic, particularly in lee terrain features. The likelihood of triggering avalanches will increase if the sun comes out, so best to avoid southerly slopes under intense sun.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
SUNDAY: A mix of sun and cloud, light northeast winds, alpine temperature -4 C, freezing level 1500 m.MONDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light west winds, alpine temperature -5 C, freezing level 1400 m.TUESDAY: Mostly cloudy, light west winds, alpine temperature -5 C, freezing level 1400 m.
Avalanche Summary
On Friday, many small to large (size 1 to 2) storm and wind slabs were explosively controlled and ski cut across the region. They were generally at treeline and alpine terrain with slab depths of 20 to 50 cm. Cornices were also reactive to explosives but were generally small.
Snowpack Summary
30 to 40 cm of new snow between Thursday and Saturday has been redistributed by strong south winds, forming reactive storm and wind slabs up to 1 m deep. Ridgelines are heavily corniced and if they fail they could trigger slabs on slopes below.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 140 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. Below this, the snowpack is well-settled and strong.
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.