A widespread natural avalanche cycle is forecast to continue on Tuesday. Travel in avalanche terrain is NOT recommended.
Weather Forecast
NOTE: Freezing levels are forecast to remain elevated overnight throughout the forecast period. This will significantly increase the impact of day time warming on the snowpack.MONDAY NIGHT: Clear / Light, northeasterly winds / Alpine low 3 / Freezing level 3000 m.TUESDAY: Sunny / Light, northeasterly winds / Alpine high 7 / Freezing level 3000 m.WEDNESDAY: Sunny / Light, southeasterly winds / Alpine high 8 / Freezing level 3000 m.THURSDAY: Sunny / Light, westerly winds / Alpine high 7 / Freezing level 2700 m.
Avalanche Summary
On Sunday, a widespread loose wet avalanche cycle to size 2.5 and numerous size 3 persistent slabs were reported on solar aspects at all elevations. A natural avalanche cycle is expected to continue on all aspects and at all elevations on Tuesday.
Snowpack Summary
15-30 cm. of well settled snow has created a cohesive slab sitting on a pile of facets (sugary snow), as well as a crust on sun exposed slopes. Natural avalanches on this layer are expected to continue.At lower elevations below treeline, a weak layer of surface hoar (weak, feathery crystals) buried in mid-January can be found approximately 50-90 cm. deep and may be combined with a crust on south aspects. The current warming event may awaken this layer, resulting in large, destructive avalanches. Steep cutblocks and large open glades at lower elevations are the most likely places to trigger this layer. Smaller loose wet avalanches may "step-down" to this deeper layer.The base of the snowpack is composed of facets (weak, sugary snow) that sit on a crust. Very large avalanches failing on this persistent weak layer will become more likely with the intense sunshine and rising freezing levels.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.