Spring conditions have taken hold. Avalanche hazard will vary from LOW in the cold mornings to possibly HIGH in the afternoon on warm and sunny days. Start early and finish early.
Weather Forecast
A spring pattern has been established these last few weeks. Cool mornings and warm/hot days are now the norm with afternoon temperatures often well above freezing. If there is a major change in the snowpack, this bulletin will be updated more frequently. Until then, avalanche bulletins will only be updated as needed. Early starts are key at this time of year.
Avalanche Summary
Wet slides either in the form of slabs or loose are occurring most days when the temperature and solar radiation increases. Cornice failures are also becoming more common. In general we are seeing slides mainly in the size 1 to 2 range, but large avalanches are possible due to the deeper weak layers. Always be thinking about consequence as you travel.
Snowpack Summary
Spring is here it would seem! The snowpack varies in its stability depending on a number of different factors. Day time high, quality of freeze overnight, aspect and influx of new load from snow or rain. In general, as temperatures warm up, stability will decrease. These decreases will be most apparent on solar aspects where the radiation is strong. Cornices could become weak and prone to failure. The timing on this decrease will vary but can be affected by overnight freeze and aspect. Poor freezes mean avalanche danger will increase quickly with warming. Northern aspects are still holding some dry snow at upper elevations but expect a battle up and down from there. The deep persistent weak facets will be with us until the snow is gone. Be sure to asses this layer as you travel. Some good corn is out there if you can get the timing right!! Start early and be home early and avoid the heat of the day.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.