The safest and best snow conditions are likely to be found around sheltered lower elevations. Expect any appearance from the late March sun to quickly destabilize wind slabs and loose snow at the surface.
Weather Forecast
Saturday: A mix of sun and cloud with continuing isolated flurries and a trace of new snow. Light west winds. Freezing level to 1200 metres with alpine high temperatures around -8.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1000 metres with alpine high temperatures around -9.Monday: Cloudy with flurries bringing 2-3 cm of new snow, increasing overnight. Light to moderate southwest winds. Freezing level to 1200 metres with alpine high temperatures around -8.
Avalanche Summary
Thursday's reports included several wind slab and storm slab releases. These were natural as well as skier triggered and ski cut, mainly from size 1 to 1.5, and occurred on a range of aspects at treeline and above.On Wednesday a couple of smaller (size 1-1.5) ski cut and skier-triggered storm slabs failed on one of the recently buried weak layers mentioned in our snowpack discussion, down 20 cm. These occurred on northwest and west aspects in the alpine.Reports from last weekend and earlier this week included several small (size 1) storm slab releases, mainly skier-triggered on steeper north to northeast-facing slopes in the alpine. A couple of larger (size 2) natural storm slabs were observed in very steep terrain during the warmest part of the day. These slabs are mostly suspected to have failed on a layer of surface hoar buried earlier this month that is mentioned in our snowpack discussion, now found down about 40-50 cm. Looking forward, newly formed storm slabs are likely to remain reactive to human triggering over the near term. Watch for intervals of solar exposure to destabilize slabs as well as promote loose wet avalanche conditions on steeper, sun-exposed slopes.
Snowpack Summary
Convective snowfall coupled with strong southerly winds brought a wind-affected 5-15 cm of new snow to the region over Thursday night. The new snow has buried a couple of recent layers of storm snow that are separated by temperature and sun crusts at lower elevations and on south aspects. Surface hoar layers have been reported between these storm snow layers on shaded aspects at higher elevations and can likely now be found at approximately 30 and 50 cm below the surface. The deepest of these surface hoar layers was the failure plane in several slab avalanches this week.New snow amounts taper with elevation and below 1800 m, reduced accumulations have buried a supportive crust on all aspects. Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, large cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.
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.