We have been finding small wind slabs and large wind drifts near the ridgetops on multiple aspects over the last week. In some areas, these slabs are resting on a slick wind crust. Winds have swirled around the compass over the last few days and have been sculpting and transporting the snow that has accompanied the last 2 storms. Over the next 12-24 hours we will see winds continuing to gust in the upper elevations into the mid 20 mph range out of the south southwest. Be aware of crossloaded areas on smaller terrain features and watch out for obvious clues like cracking or hollow sounding/feeling snow under your skis or track.
We have found a weak layer near the ground throughout the advisory area over the last two weeks that is made up of weak faceted snow or a combination of facets and old crusts left over from our early season snowpack. The weak layer of facets is fairly widespread and well developed in the upper elevations especially on the shadier aspects where early snowfall accumulated. Shallow rocky areas are also harboring this layer on other aspects. George described this problem earlier this week as a low probability/ high consequence avalanche problem...meaning you are not very likely to trigger a slide this deep but the consequences if you did would be bad. The 3-5 foot overlying slab is gaining strength which is good but is also turning into more of a hard, consolidated slab if it fails. Now is a good time to play it safe on steep shady slopes or slopes with thinner/rocky areas where you are more likely to trigger the weak layer.
This kind of problem is both difficult to trigger and more difficult to predict. Slopes with tracks on them are not a good indicator of stability as the trigger points are likely to be isolated to thin or weak spots that are hard to find or easy to miss. Remember that a lack of red flags or signs of instabilities is not a good indicator for a deep or persistent slab problem. Don't let the lack of evidence lull you into more consequential terrain or sloppy group management. Use good travel techniques(one at a time) and watch your partners if you are riding or sliding in this type of terrain.
Don't forget about our 'Know Before You Go' class coming up this Tuesday evening at the McCall Ranger District office. KBYG is a great first step or a quick review if you are planning on heading into the backcountry and want to stay safe. If you are ready to take the next step after KBYG, PAC still has room for both skiers and snowmobilers in our upcoming Intro to Avalanches class on Jan 6 and 7, registration by email is required.
No new natural or human caused avalanches have been seen or reported.
The snow that we received Friday and Saturday came in with slightly warmer temperatures but did little to form a cohesive slab. The formation of isolated wind slabs on multiple aspects near the ridge tops, on exposed upper elevation slopes, and on smaller terrain features such as gullies and sub ridges will be your main concern today.
The mountains of the PAC advisory area picked up no new snow overnight and winds were light out of the south southwest. Today expect to have partly sunny skies with winds out of the south southwest blowing 9 to 16 mph and gusts will be in the 20's. An approaching storm front will cause an increase in clouds this afternoon, and snowfall will begin tonight around midnight. By morning 1 to 4 inches should blanket the upper elevations of the advisory area, and another 4 to 10 inches are possible during the day tomorrow.
This avalanche advisory is provided through a partnership between the Payette National Forest and the Friends of 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.