Sunshine and warming are set to maintain heightened avalanche danger over the coming days. Expect stability to deteriorate as each day progresses.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
Wednesday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level rising to 1700 metres with alpine high temperatures around -6.Thursday: Mainly cloudy. Light to moderate south winds. Freezing level rising to 1900 metres with alpine high temperatures around -3. Weak overnight cooling.Friday: Cloudy with flurries beginning in the evening and continuing overnight. Moderate south winds. Freezing level to 1900 metres with alpine high temperatures around -2.
Avalanche Summary
On Sunday there was a report of a natural, cornice-triggered size 2.5 persistent slab avalanche on a west aspect at 2350 m that is believed to have failed on the mid-March layer.Friday there was a report of a natural cornice collapse that produced a size 3 deep persistent slab avalanche that failed on an early-season layer (300 cm deep) on a northeast aspect at 2600 m. Several loose, wet releases up to size 2.5, running to ground in low elevation paths were also reported on Friday.Wednesday there was a report of natural cornice failure that resulted in a size 2.5 wind slab release on a northeast aspect at 2700 m, while a skier was able to trigger a size 2 wind slab (40 cm deep and 100 m wide) on a recently buried crust on a similar aspect at 2400 m. Last Tuesday, another natural size 2.5 cornice failure was reported on a north facing alpine feature.
Snowpack Summary
About 30 cm of recent snow covers a supportive crust on all aspects to at least 2100 m (and possibly higher on south aspects), while 40-60 cm of storm snow can be found at higher elevations. Below 2200 m this new snow has a surface crust becoming moist or wet by the afternoon.Within the upper snowpack there are now several different crusts with only the shallowest of these remaining a concern as the uppermost layer of storm snow settles and bonds to it.There is some lingering concern around the mid-March persistent weak Layer in the alpine where it is found 100 to 150 cm below the surface. This buried crust/surface hoar interface is still capable of producing large avalanches if it is triggered (think step-down from a surface avalanche or a cornice collapse).Deeper persistent weak layers from December and January may be starting to become reactive to very large triggers. A recent cornice collapse is believe to have initiated a slab release on an early season layer, 300 cm deep.
Problems
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.