Loose, unconsolidated snow has been the trend for over a week creating a soft and unconsolidated upper snowpack with a firm and strong slab below it. In our pit tests Friday, we saw several of these individual storm layers that were only partially bonded to the layers below creating moderate failures in compression but lacking propagation or the energy to spread out over large areas.
Over the last 24 hours, temperatures have been on the rise along with new snow which will have likely made the storm slab that much denser than the snow below it. You could trigger a weakness in one of these layers on steep terrain resulting in a slab a foot deep or more today. Worth noting and watching is a subtle crust created by a freezing mist event that occurred mid morning on Monday. It is buried around 12 inches down in the snowpack. This was one of the layers that is failing in compression and may become more reactive now that we have added new, heavier snow on top.
Recent winds and new snow have created wind slabs in leeward terrain. Winds have been gusty throughout the week and mostly out of the S and SW. North and South Valley areas have both seen the same weather this week with cornices slowly growing and wind loading occurring on mostly E, NE, N and NW facing slopes. We observed active wind loading and scouring on a SW aspect just south of Granite Mountain Friday with loading occurring on the NE throughout the day. These slabs have gotten denser with the added new snow, and increasing temperatures.
See the photos below for a comparison of the difference in the snowpack on a SW facing slope at 7100 feet and a NNE slope at 7600 feet on Granite mountain from Friday. Notice the layering in the SW pit and the depth of the freezing mist crust and new snow between the two pits.
Please let us know what you are seeing in the West Central Mountains. Take the time to submit an observation or send us an email. It's easy and may save a life. If you are having trouble adding photos to your observation, send us the photo at our email address and we will add it to your observation. Click on the observation tab on the advisory page or email us at: email@example.com
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This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center. This advisory covers the West Central Mountains between Hard Butte on the north and Council Mountain on the south. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.