Yesterday’s storm brought 5 to 10 inches of new snow to the Greys River area. Up to two feet of snow has fallen since December 11. Persistent weak layers exist at the interface beneath this new snow and old snow surfaces that formed during a long dry period. On avalanche prone slopes, the weight of a single person could trigger a slab avalanche on this interface. At the higher elevations these slabs could be large enough to seriously injure or fully burry a person. This persistent weak layer was especially active yesterday between an elevation of 7,300 and 7,800 feet. The slides that occurred in this elevation zone were smaller than what you might trigger up higher where new snow depths are greater. This type of hazard is best managed by terrain assessment skills and conservative terrain choices. Evaluate steep slopes carefully and anticipate the potential consequences of triggering a slab avalanche of any size above terrain traps or on slopes with low snow hazards that can cause serious trauma.
At the higher elevations large slab avalanches formed by southwest to west winds could be human triggered on steep avalanche prone slopes. These slabs could be two to three feet deep. Slab avalanches triggered below an elevation of 7,500 feet are likely to be a foot deep.
( Discussion is generated from the previous day's afternoon forecast. )Snow will decrease this evening and end from north to south after midnight. Skies will be partly cloudy in the morning and are to be overcast by evening. Temperatures will be near 10 degrees by daybreak and then warm into the teens and 20s. Northwest winds will be light at 5 to 15 miles per hour.This week’s snow and wind have increased the avalanche hazard. Slab avalanches 1 to 3 feet in depth can be triggered by the weight of a single person. Persistent weak layers at the interface of the old snow surface and this week’s new snow are a concern that require your full attention. These types of hazard are best mitigated by conservative terrain choices. Evaluate steep slopes carefully and anticipate the potential consequences of triggering a large slab avalanche or a small slab avalanche above terrain traps or on slopes with low snow hazards that can cause serious trauma. The general avalanche hazard is expected to be moderate at the mid and upper elevations. At the lower elevations small avalanches are possible on isolated terrain features. Down there the hazard will be low.
