Wind slabs and wind loaded terrain remain the primary concern today. They are widespread in the upper elevations and range in sensitivity from easily triggerable to resistant. They also range in size from a few inches to a few feet in some areas. New snow over the last few days has also done a great job camouflaging some of the wind slabs formed earlier this week, so the tell tale signs may be covered. Additional winds yesterday have added to the problem and winds will increase again today. With plenty of light snow available for transport, Northerly terrain is suspect right now. You may also find crossloaded areas on SE, E and W facing aspects where smaller terrain features have caught the blowing snow. Remember that wind slabs will often allow you to get further out on them than a storm slab before they fail. Also, some of these wind slabs may be resting on a weak layer of faceted snow or surface hoar that was buried earlier in the week. Your best bet is to avoid steep, wind loaded areas right now and through the next few days.
Several different weak layers formed on or near the snow surface during the last period of high pressure and are lurking in our snowpack right now. These persistent weak layers have slowly been buried this week and have failed(natural avalanche cycle mid week) in some areas and are still waiting for a trigger in other places. These layers include buried surface hoar and near surface faceted snow on shadier aspects and a series of unsupportable and supportable crusts on the Southerly aspects. If you take 5 minutes to dig into the snow right now, you can see exactly where these layers are, they are pretty obvious in the snowpack. Surface Hoar and faceted snow are responsible for the majority of avalanche incidents and fatalities throughout the world. As we get additional snowfall combined with warming temperatures and strong winds, there is a good possibility that we will see another round of natural avalanches. The risk of human caused avalanches will be rising today and tomorrow as well. The avalanche problem is increasing in both probability and size right now and requires an attitude and mindset adjustment from what we have been seeing over the last few weeks. Gone is the time for a go for it attitude, now is the time to travel safe and avoid steep terrain.
Local ski resorts are showing 10 inches of new snow in the last 48 hours. Cooling and drying conditions Thursday and Friday nights left us with a soft and mostly unconsolidated layer of new snow above the older snow layers. This is probably why we did not get more reports of skier or sled triggered avalanches yesterday and Friday. We have seen plenty of natural activity over the last few days on Northerly and Southerly aspects though so don't be lulled into complacency by what is not happening. The layer of buried surface hoar and the collapsing crusts on the Southern exposures have the potential to get overloaded in the next 48 hours with rising temps, heavy precipitation and additional wind loading. Play it safe, avoid steeper terrain, watch your partners and make sure everyone in your group is carrying and knows how to use their rescue gear.
Rising temperatures are going to be the main story today. Expect to see a rising snowline through the day today possibly as high as 6500 feet. Winds will pick up through the day with more snow beginning late morning to early afternoon. This next storm is quite a bit wetter than our last storm and will be accompanied by strong South and Southwest winds with gusts into the mid 30's. NWS Boise office is predicting 1-3 inches today with an additional 4-8 inches over night. Other computer models are forecasting over 10 inches for the West Central and Central Idaho mountains.
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.