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
Sunday and Monday should bring warm, dry weather with light winds. The freezing level climbs to 2200 m by Sunday and rises further to 2600 m on Monday.
Avalanche Summary
On Friday, a helicopter remotely triggered a small slab on a wind loaded feature. It failed on the buried April weak layer. A skier remotely triggered a size 1 avalanche on a high north aspect on Thursday. It failed on facets down 20 cm. A naturally-triggered size 2 slab was also observed. Explosives have triggered several size 2 cornice falls over the last few days. On Wednesday, natural solar-triggered avalanches to size 2 were reported. Explosives triggered several slab avalanches and a skier triggered a size 1.5 on a convex roll feature. A remotely triggered avalanche was also triggered from 25 m away. Several remotely triggered avalanches have been reported in the last week from up 100m away. Avalanche activity is expected to continue as temperatures rise.
Snowpack Summary
Warm temperatures and strong sun are rapidly changing the upper snowpack. The snow surface is likely to become moist by day on most aspects and elevations. Overnight refreezing may form surface crusts. Watch out when there is no overnight refreeze: rapid weakening during the day is likely.A troublesome weak layer is down 20-60cm. This layer consists of surface hoar and facets overlying a melt-freeze crust. The distribution of the layer is variable, and it may be more problematic in the north of the region. 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. These layers have the potential to wake up with sustained warming, a significant rain event, and/or a big cornice fall.
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.
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.
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.