THIS AVALANCHE ADVISORY EXPIRED ON January 19, 2016 @ 6:37 am
Avalanche Advisory published on January 18, 2016 @ 6:37 am
Issued by George Halcom - Payette Avalanche Center
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The Avalanche Danger remains Considerable on wind loaded, upper elevation slopes. Buried weak layers on protected aspects will make it possible to trigger avalanches in non wind affected terrain. Six inches of new snow overnight, along with moderate winds out of the East, and South East have added fresh wind slabs on leeward slopes. Skiers reported triggering slides on buried surface hoar, about a foot and a half deep now. Play it safe and stick to low angle terrain.

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 and wind loaded terrain remain the primary concern today.  Last night, the mountains got another 6 inches of snow, and some moderate winds out of the East/ South East, creating fresh slabs on West through North slopes. Wind slabs are widespread in the upper elevations and range in sensitivity from easily triggerable to resistant. They also range in size from a few inches to a few feet in some areas. New snow over the last few days has also done a great job camouflaging some of the wind slabs formed earlier this week, so the tell tale signs may be covered. With plenty of light snow available for transport, Northerly terrain is suspect right now.  You may also find crossloaded areas on SE, E and W facing aspects where smaller terrain features have caught the blowing snow. Remember that wind slabs will often allow you to get further out on them than a storm slab before they fail.  Also, some of these wind slabs may be resting on a weak layer of faceted snow or surface hoar that was buried earlier in the week.  Your best bet is to avoid steep, wind loaded areas right now and through the next few days.

Avalanche Problem 2: Persistent Slab
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 Several different weak layers formed on or near the snow surface during the last period of high pressure and are lurking in our snowpack right now.  These persistent weak layers have slowly been buried this week and have failed (natural avalanche cycle mid week) in some areas, and are still waiting for a trigger in other places.  These layers include buried surface hoar and near surface faceted snow on shadier aspects and a series of unsupportable and supportable crusts on the Southerly aspects. If you take 5 minutes to dig into the snow right now, you can see exactly where these layers are, they are pretty obvious in the snowpack.

Yesterday,we got reports of skiers near Slab Bute and Granite Mountain triggering steep rollovers down to the buried surface hoar about a foot and a half deep now, one skier was pushed into a tree well, and buried up to his thighs. As we get more snowload on this weak layer, the likelyhood of triggering increases...we are watching this layer closely, and are finding it everywhere, especially areas that have been protected from the wind.

Surface Hoar and faceted snow are responsible for the majority of avalanche incidents and fatalities throughout the world. As we get additional snowfall combined with warming temperatures and strong winds, there is a good possibility that we will see another round of natural avalanches.  The risk of human caused avalanches will be rising today and tomorrow as well. The avalanche problem is increasing in both probability and size right now and requires an attitude and mindset adjustment from what we have been seeing over the last few weeks. Gone is the time for a go for it attitude, now is the time to travel safe and avoid steep terrain.

recent observations

Local ski resorts are showing around 2 feet of new snow in the last six days. We saw plenty of natural activity Thursday on Northerly, Easternly, and Southerly aspects so don't be lulled into complacency by what is not happening. The layer of buried surface hoar and the collapsing crusts on the Southern exposures have the potential to get overloaded with warmer temps, added precipitation, and additional wind loading.

Yesterday,we got reports of skiers near Slab Bute and Granite Mountain triggering steep rollovers down to the buried surface hoar about a foot and a half deep now, one skier was pushed into a tree well, and buried up to his thighs...Play it extra safe right now, avoid steeper terrain, watch your partners and make sure everyone in your group is carrying and knows how to use their rescue gear.

weather

Expect to see temperatures hovering just below freezing in the upper elevations today, light winds out of the SouthWest, and light snow until our next sizeable storm sets in on Tuesday bringing more wind and snow. 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Rain and snow before 11am, then a slight chance of snow. High near 34. Calm wind. Chance of precipitation is 80%. New snow accumulation of less than one inch possible. A 30 percent chance of snow after 11pm. Mostly cloudy, with a low around 20. Light south southeast wind. New snow accumulation of less than a half inch possible. Snow. High near 33. Calm wind becoming south southeast 5 to 7 mph in the afternoon. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible.
Temperatures: 34 deg. F. Low of 20 deg. F. 35 deg. F.
Wind direction: Calm S/SE S/SE
Wind speed: Calm Light 5-7
Expected snowfall: Less than one in. less than half in. 1-2 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Snow, mainly before 11am. High near 30. Southwest wind 5 to 10 mph. Chance of precipitation is 80%. New snow accumulation of around an inch possible. A 50 percent chance of snow, mainly after 11pm. Mostly cloudy, with a low around 22. South southwest wind 10 to 17 mph. New snow accumulation of around an inch possible. Snow. High near 30. Breezy, with a south wind 18 to 26 mph, with gusts as high as 38 mph. Chance of precipitation is 80%. New snow accumulation of 3 to 5 inches possible.
Temperatures: 30 deg. F. Low of 22 deg. F. 30 deg. F.
Wind direction: SW S/SW S
Wind speed: 5-10 10-17 18-26
Expected snowfall: 1 in. 1 in. 3-5 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.