Sunshine are warmth are the primary drivers of avalanche hazard. Avoid sun exposed slopes in the afternoon, and stick to higher, shady aspects for the best snow.
Confidence
Good - The weather pattern is stable
Weather Forecast
Wednesday: Mainly sunny. The freezing level climbs to around 2000 m during the day and drops below 1500 m overnight. Winds are light and variable. Thursday: Mainly sunny. The freezing level climbs to around 2000 m during the day and drops below 1500 m overnight. Winds are light and variable. Friday: Cloudy with light to moderate snow. The freezing level lowers to 1500 m and winds increase to moderate or strong from the S-SW.
Avalanche Summary
Moist loose avalanches have been reported on steep sun-exposed slopes, and one natural cornice fall (size 2) was reported on Monday. This cornice did not trigger a slab on the slope below.
Snowpack Summary
On shady slopes, 20-30 cm of low density storm snow sits on a strong and supportive rain crust that was buried last Saturday and extends as high as 2100m. Previous west-southwesterly winds have created thin new wind slabs in lee terrain, especially high N aspects. Expect an ongoing melt-freeze cycle on sun-exposed slopes. A facet/crust layer that was buried in mid-March is now approximately 50-100 cm down. Recently it was found down 55 cm near the Duffey Lake Road, and produced moderate sudden results. This remains a concern in the region because of it's potential for very large avalanches. Cornices are now large and mature and may collapse with daytime warming and intense sunshine.
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.