The wind slab problem is fairly widespread on the Northern half of the compass above 7000 feet. Wind slabs are now resting on a variety of old snow surfaces ranging from hard wind board to loose, faceted snow. You are likely to trigger these slabs not only at the ridgelines but in steep terrain below rock faces or in gullies or other confined terrain where the wind blown snow accumulated. Within the last week we have been able to intentionally trigger these slabs and last weekend skiers on Sawtooth Peak unintentionally triggered several small wind slabs.
Over the last week we have toured and traveled into some of the steepest northerly terrain and found wind slab crowns scattered across these slopes. What we also noticed is that most of these slopes that did not run on their own are still untouched by sledders or skiers still so no artificial/ human triggers have been applied yet.
Overall, you can look at windloaded terrain right now with the great visibility and see the warning signs: rounded, pillowy, sculpted terrain is the norm throughout the Northerly terrain, and these features are easy to recognize clues of where the problem areas are right now. Play it safe and stick to lower angle terrain or terrain that has not been affected by the wind until these slabs have had a chance to gain stability. Remember right now, just because you are not seeing recent avalanches on some steep northerly terrain does not mean those slopes are safe...
Granite Mt, Lookout Bowl 1/13/17 showing ripple marks left by the wind and small, loose, avalanches in the steep terrain as the sun warms up the snowpack.
With a strong inversion in place, upper elevation temperatures will be climbing to near freezing in the afternoon again today. Over the last three days, we saw signs of change in the snowpack on the southerly or solar aspects. Roller balls and small, loose avalanche activity started picking up as the day warmed with trees shedding snow and rime at the same time. Today should be a mirror image of the last two and as the warming starts, watch for an increase in the potential of loose wet slides later in the day. We saw quite a few small point release slides on sunny, rocky terrain yesterday and a wet, loose slide that stepped down into deeper layers and propagated across Osprey Point as we were driving back in on Warren Wagon on Thursday.
Hey snowmobilers and snowbikers, have you heard about the Motorized Level 1 avalanche class the Friends are hosting in Fairfield next weekend? Sawtooth Avalanche Center still has some spots open so email them at firstname.lastname@example.org for more information or to sign up, stop making excuses. This is a great class, reasonably priced with a shortened classroom session and 2 field days jam packed with useful travel, rescue and decision making information.
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Several recent avalanches and large point release slides were observed on E and NE facing slopes across the Council Mountain area yesterday. All were in steep, windloaded terrain that looked like it was warming with early am sun affect.
Also worth paying attention to right now are the near perfect conditions that are creating our next weak layers at both the upper and middle elevations. Near Surface Faceting and Surface Hoar are forming at a rapid rate. This will be our first significant persistent weak layer type of event for the winter. Near Surface Faceting is the "recycling"effect of the snow in the upper elevations in mostly shaded areas right now, below that is a perfect bath tub ring of Surface Hoar that seems to be the largest around the 6000-6800 foot zone. With a series of storms lining up next week, these layers will almost certainly be an issue as a storm slab builds on top of them this week.
Look for a continuation of the current inversion through Monday. Monday night through Sunday...Models are still advertising a pattern change which will bring more precipitation and a respite from the very cold temperatures. The upper level ridge will shift south of our area on Tuesday as strong west-southwest flow aloft from across the Pacific brings the first of a series of weather systems into the northwest U.S. Precipitation will be concentrated over our northern zones at first, but a deepening upper level trough will spread rain and snow across our entire CWA as it reaches the coast on Wednesday and moves inland on Thursday. Snow levels will rise to 5000 to 6000 feet on Wednesday then lower to around 4500 feet on Thursday as the trough pushes inland. Moderate amounts of precipitation are expected. The next trough will bring colder air and more precipitation in the form of snow at all elevations Friday and Saturday.
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.