Recent snow and strong winds have produced touchy wind slabs. Watch for signs of avalanche activity and locally unstable snow, such as whumpfing and shooting cracks.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
MONDAY: Partly cloudy, light northeasterly winds, alpine temperature -15 C, freezing level below valley bottom.TUESDAY: Mostly sunny, light westerly winds, alpine temperature near -12 C, freezing level below valley bottom.WEDNESDAY: Mostly sunny, moderate westerly winds, alpine temperature near -11 C, freezing level below valley bottom.
Avalanche Summary
On Saturday, small (size 1) loose dry and storm slabs were triggered naturally.Avalanche activity will continue as the recent snowfall begins to gain strength. Expect widespread loose dry and storm slab activity as well as wind slab activity in lee features. If triggered, these layers have the potential to release buried weak layers.
Snowpack Summary
Around 30-60 cm of storm snow with strong winds have created widespread loose dry and storm slab avalanche problems. Some of this snow has been re-distributed with strong winds, creating wind slabs on lee features. These slabs overly a layer of weak surface hoar buried mid-February that has produced very easy snowpack test results with sudden fracture characters.The lower snowpack in this region is weak with two main concerns:1) a widespread weak layer from mid-December composed of facets, crusts, and surface hoar that is 100-150 cm deep.2) a rain crust with sugary facets buried in late-November near the bottom of the snowpack. Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread.
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.
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.