Watch for variable wind loading patterns as you gain elevation and maintain avoidance of overhead hazards like cornices and large avalanche paths. A heavy trigger in the right location still risks triggering a very large and destructive avalanche.
Weather Forecast
Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1800 metres with alpine temperatures around -3.Sunday: Cloudy with sunny periods and isolated flurries with a trace of new snow. Light west winds. Freezing level to 1700 metres with alpine temperatures of -3.Monday: Cloudy with sunny periods. Light south winds. Freezing level to 1700 metres with alpine temperatures of -3.
Avalanche Summary
Reports from Thursday showed loose wet avalanches releasing both naturally and with skier traffic in steep terrain from Size 1-2. Isolated natural Size 1-2 wind slab releases were observed occurring in steep, rocky terrain as a direct result of wind loading.On Tuesday there was a natural cornice fall near Golden that did not release a slab on the slope below. On Monday there were several natural cornice falls up to size 2.5 that released storm or persistent slabs from the northerly aspect slopes below. On Sunday there was a natural cornice fall size 2.5 from extreme terrain.
Snowpack Summary
Light new snow amounts and moderate winds (mainly from the south) have formed fresh wind slabs on the snow surface at higher elevations. The new snow has buried melt-freeze crusts on all aspects below about 2200 metres and in the high alpine on solar aspects. Isolated surface hoar may be found below the new snow on shaded aspects at high elevations. Below the new snow interface, last week's storms brought 40-60 cm of snow to the region. Several other crusts as well as moist snow are likely to exist within this storm snow, mainly at lower elevations and on solar aspects. Fragile new cornice growth also occurred along ridgelines over the course of the week. At higher elevations, the February crust/facet layer is now down around 130-150 cm and the deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack. These layers were active during a storm in mid-March and produced some very large avalanches. Occasional deep releases were also reported in late March and these deeply buried weaknesses remain a serious concern as warming temperatures continue to penetrate the snowpack at increasingly higher elevations.
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.