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.
Yesterday, we toured Granite, Twin Lakes, Duck Lake and Fisher Saddle to look into some of the steepest northerly terrain and found wind slab crowns scattered across the steep north facing terrain. 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 pretty much yelling "leave me alone" 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 they 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 two 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? We still have some spots open so email us at email@example.com 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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SHORT TERM... fog is widespread in the valleys. In general, the fog is at lower elevations than it was yesterday as the inversion has become shallower but also stronger. The shallowing should continue into Sunday. A weak embedded trough in the northwest flow aloft will spread clouds over our CWA today, clearing tonight. No precipitation from these clouds. Persistence should be a good forecast for temperatures through Sunday with only light winds and little or no mixing of the surface air mass. Adjustment made for smaller diurnal range where the fog is.
LONG TERM...Sunday night through Saturday...An upper level ridge will maintain dry weather through Monday night. A pattern change will begin to affect our area starting Tuesday, as strong upper level flow from across the Pacific brings precipitation and milder temperatures. The first system will bring showers mainly to our northern zones Tuesday and Tuesday night. A second stronger system will spread precipitation across our entire area on Wednesday. Snow levels will rise, with rain expected below about 5000 feet. Precipitation will change to a mix of rain and snow Wednesday night. This system will carve out an upper level longwave trough over the westerly U.S., resulting in cooler temperatures and continued unsettled weather Thursday through 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.