Southwest winds overnight have been in the 30 to 80 mph range on Mammoth Mountain, and they are forecast to continue into the late afternoon. Snow amounts have been relatively unimpressive as of 4:00am, however showers will persist into the evening with up to 8” in areas north of Bishop. Wind can deposit snow at 3 to 5 times the rate at which it can fall from the sky which means that even modest amounts of precipitation can create deep wind slabs in favored areas. Expect small wind slab avalanches in many areas on steep, leeward slopes. Large wind slab avalanches may occur where winds have the most snow to transport – just under ridgelines, and on cross-loaded features.
Snowpack tests resulting in failures and propagation of fractures in our persistent weak layers have become fewer and farther between recently. There have been no reports of recent avalanche activity, no test slope failures, and there have been no reports of slope-wide collapsing in these layers since before last weekend. Although unlikely, an avalanche failing on one of these layers has the potential to be large and destructive. Especially worrying is the possibility that a smaller wind slab avalanche could suddenly overload one of these deeper instabilities. In isolated areas, these reactive layers have been observed between 40 to 70cm down and in areas where the snowpack is generally less than ~1m deep. Extra detective work with a shovel is required to see what these layers can do in your area.