THIS AVALANCHE ADVISORY EXPIRED ON March 16, 2016 @ 6:57 am
Avalanche Advisory published on March 15, 2016 @ 6:57 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Danger is CONSIDERABLE on upper elevation, windloaded slopes today. Skiers and riders are likely to trigger dense windslabs in steep, exposed terrain. In steep, sheltered terrain storm slabs and loose dry avalanches will be your main concern and human triggered avalanches will be possible. At mid elevations the danger is MODERATE and below 6,000' the danger is LOW. 

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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Strong south-southwest winds over the weekend combined with moderate snowfall are enough to be a cause for concern today. Cautious and conservative decision making and route finding will be the key to staying safe today in the mountains. Multiple different generations of windslabs are making up the top 5-30" of our snowpack and will range from touchy in less exposed areas to stubborn on more exposed and wind affected slopes.  Keep an eye out for visual and tactile clues of windslabs today: drifted, sculpted and pillowy looking areas below ridgelines and further downslope under headwalls or cliffbands are great signs of wind deposited snow.  Hollow, or drummy areas of the snowpack or a normally expect. South winds are also good at crossloading smaller features mid slope like gullies or small terrain features, especially on East and West aspects. The bottom line is inspect all slopes before committing to them. Also, cornices are suspect right now due to significant growth with the recent wind events. Keep far back from all ridgelines with cornices, especially ones over consequential terrain.

Avalanche Problem 2: Loose Dry
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A combination of dry, loose avalanches and lingering storm slabs will be found on steep, wind protected terrain today. Multiple layers of grauple can be found in the upper 12-20 inches of the snowpack. Grauple is a good snow type for fast moving loose,dry avalanches and can pick up additional material quickly when it starts moving.  It also can make a good weak layer for some of the dense storm slabs left over from last weekend's storms. A few additional inches of dry and light snow above the denser snow below will also compound the loose, dry problem. These small sluffs can easily push you or your sled where you don't want to go or into or over obstacles below.  Shallow storm slabs may also be found in protected terrain where the new snow is resting on a variety of old snow surfaces including old crusts and buried grauple layers.  These slabs may be soft or more dense based on the elevation and temperatures while it was snowing. You can expect to see these mid slope or on slopes that were protected from the wind and windloading over the last few days.

recent observations

A combination of high winds and warm snow falling on Saturday and Sunday made for a very dense snowpack with some light and dry snow on top yesterday.  South Valley definitely was favored with the last round of storms but Northern areas were slightly more protected from the strong South and Southwest winds.  Be on the lookout for the obvious signs of windloaded slopes, SIGNIFICANT wind transport occurred throughout the West Central Mountains on Saturday and Sunday. Cornices have added a new layer of sensitive, dense growth and should be avoided today.  Windloaded E/NE,N and NW slopes are prime for a human trigger right now. Give these windloaded slopes a wide berth today and know what's above you if you are playing on lower angle slopes in the northerly aspects today.

weather

Today we will get a break from the winds and an additional 2-4 inches of snow in the mountains with light accumulations in the valley.  Temperatures will be slightly below normal but slowly increasing through the week. By Sunday we will be back to 10 degrees above average. Expect a fair amount of grauple to fall and note where it is pooling if you are out in the mountains today.  Significant grauple acculations over the last 2 days are adding to our current storm instabilities and the loose, dry avalanche problem.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow showers likely. Cloudy, with a high near 32. Southwest wind around 6 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible. A 40 percent chance of snow showers, mainly before midnight. Cloudy, with a low around 16. West southwest wind around 5 mph becoming calm in the evening. New snow accumulation of less than a half inch possible. A 20 percent chance of snow showers. Cloudy, with a high near 37. Calm wind becoming southwest around 6 mph in the afternoon.
Temperatures: 32 deg. F. 16 deg. F. 37 deg. F.
Wind direction: SW W/SW SW
Wind speed: 6 5, becoming calm in the evening 6
Expected snowfall: 1-2 in. Trace in. 0 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow showers. High near 28. West southwest wind 9 to 11 mph. Chance of precipitation is 100%. New snow accumulation of 2 to 4 inches possible. A 50 percent chance of snow showers. Cloudy, with a low around 15. West wind 5 to 9 mph. New snow accumulation of less than one inch possible. A 30 percent chance of snow showers. Cloudy, with a high near 33. West southwest wind 6 to 11 mph. New snow accumulation of less than one inch possible.
Temperatures: 28 deg. F. 15 deg. F. 33 deg. F.
Wind direction: W/SW W W/SW
Wind speed: 9-11 5-9 6-11
Expected snowfall: 2-4 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.