Persistent slabs, resting on weak faceted snow near the crust buried on March 7th are becoming reactive on the northerly half of the compass above 7,500ft. Multiple, large human triggered avalanches were reported yesterday that broke on these buried layers. Some of these avalanches occurred in areas that slid during the early January cycle, so knowing the seasonal history of a slope can be helpful information when choosing terrain. Assessing the stability will be difficult without digging deep enough into the snowpack to assess old layers. Above 9,000ft, near ridge crests and on steep leeward slopes there is also a possibility for wind slabs up to two feet thick. Below 7,500ft avalanches are unlikely.An avalanche fatality in the south fork of Game Creek near Victor, ID occurred yesterday afternoon. Additional details will be made available as they are confirmed. Our heartfelt condolences go out to the friends and family of those involved.
Soft slabs have the potential to fail on buried facets deeper in the snowpack. These slides can have depths of two to four feet, propagate long distances, and may be remotely triggered from lower angle or adjacent terrain. Increased safety margins can help reduce uncertainty.
Shifting winds have formed wind slabs in steep upper elevation terrain. Recent snowfall was loaded onto slick crusts and variable surfaces. Look for smooth pillows and loaded terrain features. These slabs could have depths of one to two feet. Cracking in the recently loaded snow is a clue that slabs are becoming reactive.
Skies will be partly cloudy in the morning and increase to mostly cloudy in the afternoon ahead of an approaching weather system. Temperatures will start in the teens in the mountains and twenties in the valleys and then warm to the forties up to 8,000 feet and thirties at 10,000 feet. Southwesterly ridgetop winds are expected to be 10 to 20 miles per hour and increase into the twenties in the afternoon.The avalanche hazard is expected to be Moderate above 8,000 feet in all three forecast areas. It will be possible for the weight of a single person to trigger a small to large avalanche on steep terrain. Although these persistent weak layers are present in all the forecast areas, their depth and distribution vary greatly. It is also difficult to know the exact location of these layers due to the large amount of spatial variability. The avalanche activity seems to be occurring in areas that had a shallow snowpack prior to the March 5 snowfall. Tomorrow, sunny skies and warm temperatures will increase the likelihood of triggering these large avalanches as well as result in small wet loose slides. Heightened avalanche conditions exist and backcountry travelers should evaluate the snowpack and identify areas of concern.
