Danger ratings reflect conditions during the hottest parts of the day. Time your travel to take advantage of cool temperatures.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Precipitation ends on Saturday, leading into three days of warm, dry weather with light winds. The freezing level climbs to 2200 m by Sunday and rises further to 2500 m on Monday.
Avalanche Summary
On Thursday, a naturally-triggered size 2.5 wind slab was observed on a NE aspect at 2000 m. Numerous loose wet avalanches also failed in response to warming. On Wednesday, loose wet avalanches to size 1.5 were reported below 2100m. Widespread wind slabs were reported in the alpine and treeline. Recent whumpfing suggests human-triggered slabs may still be possible, with highest concern on sheltered north aspects. Sun and rising temperatures are likely to lead to avalanche activity wherever the snow is warming up.
Snowpack Summary
Warm temperatures and strong sun are rapidly changing the upper snowpack. On Thursday, a moist snow surface was reported to 2300m elevation on north aspects and is expected to ridgetop on solar aspects. Overnight refreezing is expected to form a widespread surface crust. Down 30-40cm is a weak layer that was buried last Friday and has been reactive recently. This layer consists of surface hoar and facets overlying a melt-freeze crust. In exposed alpine terrain, recent strong SW winds formed wind slabs in leeward features. Large cornices exist and may become weak with daytime warming. There are three dormant persistent weak layers that we are continuing to track. The late-March crust is down 50-70cm and was reactive last week during the warm period. The mid-March and mid-February layers are typically down between 70 and 100cm and have been dormant for several weeks. At the base of the snowpack, facets exist. These layers have the potential to wake up with sustained warming, a significant rain event, and/or a big cornice fall.
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.
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.