It is still possible to trigger a shallow or deeper wind slab on multiple upper elevation aspects. Winds gusting into the 40+mph range hammered the upper elevations Friday and Friday night. Expect these slabs on East through W facing aspects in all open, exposed terrain. NE, N and NW will have the deepest deposition with more shallow crossloaded areas found on upper elevation East and West facing terrain features.
Snow totals over the last 5 days have been impressive. The PAC advisory area looks like it has a mid winter snowpack on the ground already this season. The storm slab that we are concerned about is mostly unconsolidated but continues to grow in depth. Changes in temperatures over the last few days have left a series of subtle layers in the snowpack that will fail under the weight of a skier or snowmobiler on steep slopes. We have heard numerous reports of sleds in protected terrain triggering these layers in the 12-18 inch range which correlates exactly with what we have been finding in our snow pits. We have also seen quite a few naturals avalanches over the last few days in these layers on steep rollovers and other unsupported slopes. We are going to be adding another load of snow starting tomorrow which will only increase this problem.
Loose dry avalanches or sluffs are becoming more of a problem. We have a lot of unconsolidated snow on the ground, if you are in steep or confined terrain these small slides can push you off course and into or over obstacles you would rather avoid. Be aware of where your partners are and don't push a sluff down on to them. As the snow gets deeper this problem will continue to be a problem.
During the week last week, PAC forecasters encountered layers of buried surface hoar in both the Northern and Southern ends of our advisory area. These layers were not widespread or well formed and were created during very brief periods of clearing and cooling between storms. These layers should continue to degrade with the weight of the new snow smashing them down. Keep in mind that you may still encounter these in isolated, wind protected areas. If you are digging around and find these layers, please shoot us an email or enter an observation to let us know where you found them.
We saw and had reports of soft slabs breaking loose in steeper terrain yesterday. These slabs are releasing between 12 and 18 inches down in the new snow layers that have accumulated over the last 4-5 days. Wind loaded areas continue to be our primary concern.
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Look for partial clearing this morning and cooler temperatures today with light accumulations possible in the mountains. Another strong winter storm will enter our area tomorrow with pre-frontal winds gusting into the high twenties and mid thirties. A strong NW zonal flow will provide nearly continuous precipitation through Thursday night with a strong cold front entering the area toward the end of the week and keeping temperatures below normal.
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.