THIS AVALANCHE ADVISORY EXPIRED ON January 21, 2016 @ 7:02 am
Avalanche Advisory published on January 20, 2016 @ 7:02 am
Issued by Dave Bingaman - 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 also make it possible to trigger avalanches in non wind affected terrain. Another 5 inches of snow fell overnight with moderate SE to SW winds adding to the wind slab problem on leeward slopes. Skier/sled triggered slides and natural avalanches continue to be reported throughout the area and will be possible again today.

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 continue to be the primary concern.  Overnight the mountains picked up another 4-5 inches of snow, and some moderate winds out of the SE, S and SW adding more snow in areas that are already suspect.  Sensitive wind slabs may be found on SE, E, NE, N, NW and W facing terrain. 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 you may not see any visual clues. These slabs range in density between soft and hard which means they may let you get well out onto them before they fail.  We have been intentionally triggering relatively large avalanches with relatively small cornice bombs in these areas which means they are more likely to fail under a skier or snowmobiler.  Also, some of these wind slabs may be resting on a layer of  weak, faceted snow or surface hoar that was buried last week.  Your best bet is to avoid skiing or riding 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 covered over the last 7 days and have failed 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. You can see 2 different layers in the crown in the photo below, the upper is the wind and storm slab and the lower is the buried surface hoar. Buried surface hoar and faceted snow have the ability to propagate or spread out over large areas when they fail and are responsible for most avalanche incidents and fatalities.

 

recent observations

PAC forecasters and public observers continue to report natural and human caused avalanche activity.  Here are a few pictures from Lick Creek and from Ride McCall's facebook page.  Please take the time to send us an email if you see or trigger avalanches in the area. You can also send us your observations and photos through our website by clicking on the Observations tab.  This information is vital to PAC forecasters and may help save a life.

weather

Light snow showers will continue through the day with 1-2 inches of additional accumulation.  Temperatures will drop slightly this afternoon as a NW flow develops. Another round of snow showers will enter the West Central Mountains tomorrow with light accumulations possible.  The long term forecast shows a good chance of another round of moisture on Saturday and a series of small Pacific storms lined up over the next 7 days. Temperatures are expected to be slightly above average with snow lines between 3500 and 4500 feet. Expect breezy SW and W winds as unsettled weather lingers over the West Central Mountains.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Snow showers, mainly before 11am. High near 30. South southwest wind 3 to 5 mph. Chance of precipitation is 90%. Total daytime snow accumulation of around an inch possible. Patchy dense fog after 8pm. Otherwise, mostly cloudy, with a low around 12. Calm wind. A 20 percent chance of snow. Cloudy, with a high near 32. Calm wind.
Temperatures: 30 deg. F. 12 deg. F. 32 deg. F.
Wind direction: S/SW calm calm
Wind speed: 3-5
Expected snowfall: 1 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: Snow showers, mainly before 11am. High near 28. West wind 7 to 15 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 3 inches possible. Mostly cloudy, with a low around 19. South southwest wind 7 to 13 mph. A 20 percent chance of snow. Cloudy, with a high near 34. South southwest wind 13 to 18 mph.
Temperatures: 28 deg. F. 19 deg. F. 34 deg. F.
Wind direction: w S/SW S/SW
Wind speed: 7-15 7-13 13-18
Expected snowfall: 1-3 in. Trace in. Trace 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.