The amount of new snow and wind effect that we have received in the last few days has created dangerous conditions on many upper elevation slopes. Wind slabs are growing, sliding, and re-forming daily. Natural wind slab avalanches have been observed over the last few days. Some of these slabs are easy to feel or see but some are also getting covered up with the new and wind blown snow and will be difficult to recognize. Shooting cracks or hollow, sculpted snow are warning signs of wind slabs. Travel in wind loaded avalanche terrain is not recommended. Check out this short video of brittle wind slabs on a SW aspect from Tuesday. Tamarack Ski Patrol also reported large avalanche activity that occurred both naturally and during avalanche mitigation operations yesterday. The possibility of rain combined with warming temperatures today may be enough to trigger another round of natural activity on slopes that have not avalanched yet. Cornice failures are a concern today as well. give warming cornices and slopes below them a wide berth today.
The amount of snow that has hit the West Central Mountains has been a big load really fast and pretty atypical for such a short time frame. Temperature fluctuations and high winds have created slabs of various hardnesses across multiple slopes. Crusts, multiple graupple layers and other weak layers exist within the snowpack and are buried 2-3 feet deep. A warming trend with the possibility of rain in the lower elevations will add to the problem with warm snow falling on colder snow below. Travel on steep slopes in the backcountry is not recommended at this time. Wait for the snow and storms to calm down and allow the snowpack to adjust to the rapid loading. More snow today and through tonight will add to the problem. Rain and warming temperatures this afternoon will increase the hazard on all slopes, especially lower elevation slopes.
Tuesday we were able to trigger D1+ sluffs on slopes with small cornice bombs. We also saw significant sluff piles at the bottom of the steep terrain near Clow Point. If you are skiing or riding slopes approaching 35 degrees you will have sluffs moving with you. Some of these may be big enough to knock you off your skis or sled and push you into trees, off rocks or into other hazards. Be aware of terrain traps that could allow sluffs to pile up deep. Rain or warming temperatures today may increase the possibility of natural wet or dry loose snow avalanches.
PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.
Please be aware that there are areas that are CLOSED to motorized traffic in the McCall, Goose Lake and greater West Mountains area. Just because there are tracks in some areas, does not mean they are open. Please respect all users and closures. See the Payette Winter Travel Maps for clarification. Both the East and West maps can be downloaded on the Avenza app on your phone or are available at trailheads and local shops. IT IS YOUR RESPONSIBILITY TO KNOW WHERE YOU ARE AND WHERE THESE CLOSURES EXIST.
We had a fairly clear day Tuesday in between storms and were able to see Natural Avalanches on several upper elevation, wind loaded slopes. In addition, slopes over 35 degrees were sluffing naturally and shedding some of the new snow. Our 600's were challenged on all but the flattest terrain and we found challenging skiing conditions on Southerly, wind exposed slopes where stiff, wind slabs were cracking under the weight of our skis and failing on isolation in our pits(see video) Deep snow is keeping sleds off steep slopes for now and avoiding the steeps for the next few days is the best thing you could do right now.
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.SHORT TERM...Today through Saturday...Warm front oriented
east-west across our southern zones this morning will shift
north during the day. Behind the warm front is a sharp rise
in snow levels. By this afternoon snow levels will range
from 6000 feet in northern zones to 7000 feet in the south.
The warm front will also bring a lot more pcpn, either as
rain or as snow changing to rain. Water content will average
around a full inch in the Boise Mountains where heavy rain
and high-mountain snow will continue. The recent heavy snow
in the mountains should absorb much of the rain. Elsewhere,
water content will average 1/3 to 2/3 of an inch with largest
amounts in Malheur County, the Lower Treasure valley, and
Weiser River Valley. Pcpn will decrease from south to north
later today and this evening.
Next will come the cold front, expected in eastern Oregon tonight
and western Idaho Friday morning. The front will bring more
showers followed by rapidly lowering snow levels, and several
inches new snow in the mountains. The front will also bring
gusty winds as it passes. Showers of snow, or rain changing
to snow, will continue through Saturday as the main upper
trough passes through the area.
Temps will be mild today and tonight, then cooling Friday
.LONG TERM...Saturday night through Thursday...A long wave
trough will persist over the region through Sunday with snow
showers in higher terrain and temperatures well below normal.
Northerly flow will provide a break in unsettled conditions
before the next system approaches from the north on Wednesday,
spreading light snow showers across the region into Thursday.
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.