A widespread natural avalanche cycle is forecast for Monday. 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.SUNDAY NIGHT: Clear / Light, northerly winds / Alpine low 0 / Freezing level 2600 m.MONDAY: Sunny / Light, northerly winds / Alpine high 6 / Freezing level rising to 3000 m.TUESDAY: Sunny / Light, southerly winds / Alpine high 7 / Freezing level 3000 m.WEDNESDAY: Sunny / Light, southerly winds / Alpine high 7 / Freezing level 3000 m.
Avalanche Summary
On Saturday, small cornice failures triggered small (size 1.5) slab avalanches on the slopes below. Cornice failures are expected to trigger large avalanches during the next few days.On Friday, two naturally triggered, size 2-2.5, persistent slab avalanches were reported on solar aspects in the alpine. Another persistent slab, size 2 avalanche was remotely triggered by a skier from 5 m. away on a southeast aspect at 2300 m. in steep, rocky terrain. Human triggering of these persistent slabs is expected to increase with the forecast sunshine and warming.
Snowpack Summary
30-60 cm. of recent storm snow is sitting on a pile of facets (sugary snow), as well as a crust on sun exposed slopes. The recent storm snow has settled into a cohesive slab and is ripe for human triggering. This persistent slab is currently our primary concern.At lower elevations below treeline, a weak layer buried in mid-January can be found approximately 50-90 cm. deep. This layer consists of surface hoar and facets, and may be combined with a crust on south facing slopes. This layer has recently been unreactive, however, the forecast 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.The lower snowpack is generally considered to be strong in most areas; except for rocky areas in the alpine with a shallow snowpack where multiple days of intense sunshine and warming could trigger sporadic very large avalanches running to valley bottoms.
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.
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.
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.