Warmer temperatures and solar radiation will increase the avalanche danger for the weekend. Variability in snowpack depth and the potential for triggering a large avalanche on the deep persistent layers mean routes should be chosen conservatively.
Weather Forecast
A ridge of high pressure will continue to dominate with mainly clear skies and dry conditions until Sun. An inversion is forecast for Fri and Sat which could bump temperatures above freezing in the alpine. Winds in the valley bottom could be strong but are forecast to be mainly light W/NW at ridgetop. Sun will be cooler and with a few flurries.
Snowpack Summary
10cm of snow arrived Wed with no wind . Under this is sun crusts on SE-SW slopes, wind effected surfaces in any open area, or faceted snow or surface hoar on sheltered areas. 30 to 40 cm above the ground weak, facetted snow remains a concern on steep or unsupported planar slopes and in the thin areas found with this highly variable snowpack.
Avalanche Summary
There has been very little avalanche activity observed in the Park in the last week. Although avalanche activity may decline in this stable period, remember that this problem will be with us for some time to come
Confidence
Timing or intensity of solar radiation is uncertain
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.