Expect avalanche danger to rise during the day, particularly on sun-exposed slopes. Plan to start your day early and move away from large sun-drenched slopes during the heat of the day.
Weather Forecast
WEATHER SUMMARY: It will be a sunny and warm week! Temperatures will steadily climb each day with the freezing level reaching at least 2500 m by Thursday (treeline temps near +5). Ridge winds should be generally light from the NW-NE.
Avalanche Summary
There was one report of a size 2 natural cornice fall on Sunday that did not trigger a slab below. No new slab avalanches were reported on Saturday or Sunday. Explosives control on Friday produced a few size 2-2.5 cornice releases, but none of these triggered slabs below. There was one report of a natural cornice fall on Friday that did trigger a size 2.5 slab, releasing at or near the ground in places.
Snowpack Summary
Thin new wind slabs have formed in exposed lee terrain in the alpine and at treeline. Southerly aspects should go through a daily melt-freeze cycle throughout the week. Buried persistent weak layers continue to be a concern for remote triggering in isolated areas where crusts are not strong enough to "bridge" the weakness. The late February surface hoar/crust layer is down 40-90 cm. This layer may continue to react to human triggers during periods of strong solar radiation and high daytime temperatures. Loose wet avalanches in motion, or cornice falls may step down to deeply buried weak layers. Cornices continue to be described as large and fragile, and may fail with forecast warming and strong sunshine this week. Conservative terrain without overhead hazard is a good strategy for avoiding the persistent slab problem.
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.