THIS AVALANCHE ADVISORY EXPIRED ON January 30, 2016 @ 6:52 am
Avalanche Advisory published on January 29, 2016 @ 6:52 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The avalanche danger is CONSIDERABLE for elevations above 6,000 feet. Additional snow and winds around 37 MPH out of the South today will increase the likelihood of  human triggered avalanches, and the possibility of natural avalanches on wind loaded slopes. If one of these wind slabs were to step down to the buried surface hoar it could be quite large. Below 6,000 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 today's incoming snow and wind, 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. Over the last 2 days, 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 over the next 2 days, 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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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. 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. As temperatures rise with the incoming warm and wet storm, the possibility of loose dry avalanches will wane.

advisory discussion

Upcoming Events: 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

Yesterday, 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

We should see 3-5 inches of more snow today along with Strong winds out of the South upwards of 37 MPH. Tonight we will see more moderate, 10-15MPH winds, but a shift from the Northwest bringing colder temperatures and another 2-4 inches of snow...Tomorrow, the wind and snow will be a bit lighter out of the west southwest, and 1-3 inches of snow forecasted.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Snow, mainly after 11am. High near 34. Calm wind becoming south 5 to 8 mph in the afternoon. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible. Snow before 11pm, then a chance of snow showers after 11pm. Low around 20. South wind 5 to 7 mph becoming calm in the evening. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible. Snow showers likely, mainly after 11am. Cloudy, with a high near 27. Calm wind becoming southwest around 5 mph in the afternoon. Chance of precipitation is 60%. New snow accumulation of less than one inch possible.
Temperatures: High 34 deg. F. Low 20 deg. F. High 27 deg. F.
Wind direction: South South Southwest
Wind speed: 5-8 5-7-calm 5
Expected snowfall: 1-3 in. 1-2 in. less than one in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Snow, mainly after 11am. High near 31. Breezy, with a south wind 9 to 14 mph increasing to 23 to 28 mph in the afternoon. Winds could gust as high as 37 mph. Chance of precipitation is 100%. New snow accumulation of 3 to 5 inches possible. Snow before 11pm, then snow showers likely after 11pm. Low around 16. Breezy, with a southwest wind 19 to 24 mph becoming west northwest 10 to 15 mph in the evening. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. Snow showers likely. Cloudy, with a high near 23. West southwest wind 7 to 9 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Temperatures: High 31 deg. F. Low 16 deg. F. High 23 deg. F.
Wind direction: South West-northwest South
Wind speed: 23-28, Gusts to 37MPH 10-15 7-9
Expected snowfall: 3-5 in. 2-4 in. 1-3 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.