Freezing levels and solar radiation are key elements to be aware of. This will be the first pulse of heat to a weak snowpack this weekend so watch temps, freezing levels, aspects and cloud cover.
Weather Forecast
Temperatures on Saturday are forecast to be more spring like with freezing levels climbing to 2000m by mid afternoon. No new precip is forecast and winds are forecast to calm down into the light to moderate range out of the SW. The big thing to pay attention to will be the solar radiation. Strong solar input will quickly decrease stability on solar aspects especially in steep thin rocky terrain.
Avalanche Summary
Numerous loose dry avalanches up to sz 1.5 were observed on Friday. Field teams were in before the temperatures really warmed up so there also may have been a few loose wet on steep solar aspects later in the day.
Snowpack Summary
10-15cm of snow fell (drainage dependant) through convective flurries over the past 24hrs. This snow tapers to only a few cms at lower elevations. The previous warm temps have created widespread temperature crusts on solar aspects up to 3000m. Windslabs from the moderate SW winds on Friday are evident in alpine terrain up to 20cm thick. These slabs are overlying the previous facetted surface and if they initiate, they are quick to entrain the weak lower snowpack and run far. Watch for these wind slabs overlying this weak facetted base and also be aware of awakening the lower down basal facets from a thin weak area.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.