Recently formed wind slabs are expected to remain reactive to triggering on Tuesday. Use extra caution on high elevation north aspects.
Weather Forecast
Mostly cloudy conditions are expected on Tuesday with snowfall beginning in the afternoon or evening. Alpine wind is expected to be light on Tuesday morning and progressively become strong from the southwest by Tuesday evening. Freezing levels are expected to reach around 1500 m on Tuesday afternoon. 10-20 cm of snow is forecast for Tuesday night and another 20-30 cm is forecast for Wednesday. Alpine wind is expected to be strong from the south or southwest and freezing levels are forecast to reach around 1600 m on Wednesday. The storm is forecast to taper off Wednesday night and a mix of sun and cloud is currently expected on Thursday.
Avalanche Summary
On Sunday, a natural cornice release triggered a size 3 slab avalanche which release down 60 cm and ran to valley bottom. Another natural size 2 cornice release did not trigger a slab. Skiers were triggering size 1 soft slabs in wind loaded features. On Saturday, a few natural storm slabs up to size 2 were reported. Numerous natural loose wet avalanches up to size 1.5 were observed on southeast through west aspects. On Tuesday, recently formed wind slabs are expected to remain reactive to human triggering. These slabs are expected to be particularly touchy where they overlie a melt-freeze crust.
Snowpack Summary
Widespread melt-freeze conditions are expected on all aspects and elevations except for high elevation north facing terrain. On all aspects below around 2000 m and higher on sun exposed slopes, there may be multiple crust layers in the upper snowpack including the late-March rain crust which is now typically down 60-80 cm. In high north facing terrain, 20-40 cm of storm snow accumulated over the weekend. Recent strong alpine wind from the south has redistributed this new snow and formed wind slabs in the alpine and at treeline which may overlie a crust. Large cornices exist primarily on north aspects in the alpine.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.