Fresh snow, and potentially a fresh wind slab problem, await you if you manage to get up high in the mountains on Tuesday. However, this brief change gives way to another heat wave later in the week.
Weather Forecast
TUESDAY: Mainly cloudy with a chance of showers/flurries in the afternoon. The freezing level dips to around 1400 m overnight and rises to 1500-1600 m during the day. Winds are moderate to strong from the West. WEDNESDAY: Flurries/showers early, then clearing. The freezing climbs to 2500 m and winds are light to moderate from the West. THURSDAY: Mainly sunny. The freezing level continues its ascent up to 3000 m. Winds should ease to light and variable.
Avalanche Summary
Recent soaring temperatures and strong sunshine have resulted in significant natural avalanche activity for the past several days. Slab avalanches to size 2.5 have been very common over the last few days on almost all aspects (the exception being high elevation north). Large loose wet avalanches and cornice falls have also been a common theme. Cloud cover and slight cooling might halt natural activity briefly on Tuesday.
Snowpack Summary
Recent warm temperatures, weak/non-existent overnight refreeze, and rain have moistened the upper snowpack at all elevations. Slopes above 1800-2000 m could have a healthy dusting of snow (up to 15 cm) by Tuesday morning, with the possibility of fresh winds slabs in exposed lee terrain. Below 1400 m, the snowpack is likely fully isothermal. The March 20th rain crust is present to around 2000 m, but the warm temps have likely allowed the overlying 30 to 50 cm of snow to bond well. Once it freezes, this layer should not be much of a concern. The late February persistent weak layer is now down 80 to 160 cm below the surface. While it may be a concern in isolated terrain, it would probably take a large trigger like a cornice fall or surface avalanche in motion to provoke it.
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.
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.