THIS AVALANCHE ADVISORY EXPIRED ON January 31, 2016 @ 5:22 am
Avalanche Advisory published on January 30, 2016 @ 5:22 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The avalanche danger remains CONSIDERABLE for elevations above 7,000 feet. About a foot of new snow, and winds around 37 MPH out of the South have moved a lot of snow ,creating the likelihood of  human triggered avalanches, and the possibility of natural avalanches on wind loaded, West through East slopes. If one of these wind slabs were to step down to the buried surface hoar it could be quite large. Below 7,000 feet the danger is Moderate.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Wind slabs continue to be a problem in the upper or wind exposed middle elevations. With the snow and wind over the last 48 hours, expect to find fresh wind slabs on north, northeast, and east aspects. You are most likely to find these slabs at or near the ridgetops or in exposed terrain above 7,000 feet. They are still relatively widespread in the upper elevations and range in sensitivity from easily triggerable to resistant. Shallow wind slabs are more likely right now but you may also find some deeper ones still lingering under a layer of new snow. These slabs range in density between soft to hard, which means they may let you get well out onto them before they fail. Also, some of these wind slabs may be resting on a layer of faceted snow or surface hoar that was buried almost two weeks ago. If you were to trigger an avalanche it could step down to this weak layer causing for a large, possibly lethal avalanche. Your best bet until our snowpack begins to 'heal' is to take the time to assess the snowpack on each slope before you commit. Or safer yet, stick to slopes that are less than 30 degrees.

Avalanche Problem 2: Persistent Slab
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A weak layer, Surface Hoar, was buried 2 weeks ago and began producing natural and human triggered avalanche activity in sheltered terrain in the northern half of the PAC advisory area. This layer has been slowly covered, and has failed in some areas, and is still waiting for a trigger in other places. Buried surface hoar and faceted snow have the ability to propagate over large areas when they fail and are responsible for most avalanche incidents and fatalities. This past week, a fresh crop of Surface Hoar has grown on the snow surface making skiing even better, unfortunately, this may become our next weak layer. As the snow begins to accumulate, you will want to take a look at the snowpack and see how the new snow is bonding with this most recent round of surface hoar.

Avalanche Problem 3: Loose Dry
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Nearly a foot of new snow over the last couple days should have loose avalanches on your mind. If you are skiing in steeper terrain today, you will need to anticipate sluff activity and have a plan so you don't get knocked down or off course. In confined terrain, sluffs can pile up and gain momentum pretty quickly. We saw some fairly decent natural Loose Dry avalanche activity this week in a steep, north facing terrain. The largest was in a confined gully, possibly resulting from a cornice failure.

advisory discussion

Upcoming Events: Today, McCall Winter Sports Club's Hometown Races and Après Ski Party Saturday, January 30th Reister Online at: www.mccallwintersportsclub.org Brundage Mountain Resort and Bear Basin Nordic Ski Center Hometown Races 3 Race Categories Vertical Challenge: 11 am Start at Brundage Endurance challenge. Racers skin up, check-in with the volunteer up top of run then ski down. Runs include: Sensation, Celebration, Lower Temptation. Winner is the person who can do the most check-ins in an hour. Nordic Race: 10 am Start at Bear Basin Nordic Center U-8 and U-6 - 1 km U-12 and U-10 - 2 km U-14 - 3 km U-18 and U-16 and open race - 5 km Open race - 10 km All ages friendly timed obstacle course and jump competition to follow races. Points for style and distance in the jumps. Obstacle course featuring the popular parachute tunnel and limbo. Combi: 1 pm Start at Brundage. A fastest time wins race. Skiers will race through a series of panels, single pole, and stubby gates, as well as a few other surprises down Griz and Badger. Individual or Team Format

recent observations

Thursday, we toured out to Grassy Twins to look at a reported natural avalanche that failed on an East aspect down to buried surface hoar about 90cm down that was resting on a sun crust.

 

We aslso observed some decent sluffing or loose dry avalanche activity on a steep Northerly slopes this week. Most recently up Trail Creek on Thursday, PAC Forecasters were unable to locate the layer of buried surface hoar in our NNE pit at 7900 feet that we have been discussing recently. However, that does not mean that it is not out there. They did find some shallow instabilities in the upper portion of the snowpack that failed in Compression Tests at density changes between the new and older, firmer snow below. CT scores were 12 and 18 at the 25 and 35cm layers.

weather

Along with cooler temperatures, today, we should see 1-2 inches of more snow along with winds out of the Southwest around 9 MPH. Tonight another 1-3 inches will fall with some moderate winds out of the southwest. 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers likely, mainly after 11am. Cloudy, with a high near 28. Calm wind becoming southwest around 5 mph in the afternoon. Chance of precipitation is 60%. New snow accumulation of less than one inch possible. A 50 percent chance of snow showers, mainly before 11pm. Cloudy, with a low around 10. South wind around 6 mph becoming calm in the evening. New snow accumulation of around an inch possible. A 30 percent chance of snow showers, mainly after 11am. Mostly cloudy, with a high near 25. Calm wind. New snow accumulation of less than a half inch possible.
Temperatures: High 28 deg. F. Low 10 deg. F. High 25 deg. F.
Wind direction: Southwest South Calm
Wind speed: 5 6-calm 0
Expected snowfall: Less than one in. 1 in. less than one half in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Snow showers, mainly after 11am. High near 24. Southwest wind around 9 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible. Snow showers likely, mainly before 11pm. Cloudy, with a low around 13. South southwest wind 8 to 13 mph becoming light and variable after midnight. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible A 40 percent chance of snow showers, mainly after 11am. Mostly cloudy, with a high near 21. West wind around 6 mph becoming calm in the morning. New snow accumulation of less than a half inch possible.
Temperatures: High 24 deg. F. Low 13 deg. F. High 21 deg. F.
Wind direction: Southwest South/Southwest- variable West
Wind speed: 9MPH 8-13-Light 6
Expected snowfall: 1-2 in. 1-3 in. Less than one half in.
Disclaimer

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.