THIS AVALANCHE ADVISORY EXPIRED ON January 5, 2017 @ 6:33 am
Avalanche Advisory published on January 4, 2017 @ 6:33 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The avalanche danger is MODERATE on all slopes over 30 degrees and above 7,000 feet due to human triggered avalanches being possibleBe on the lookout for fresh new wind slabs and older/stiffer wind slabs while traveling in steep, wind drifted slopes, especially those facing the north half of the compass.

Below 7,000 feet, and out of the wind, generally safe avalanche conditions exist and the avalanche danger is LOW

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

You can still find the affects of the wind from the weekend and the end of last week. Most of the wind transported snow has accumulated on the northerly aspects falling on older windslabs. Some of these older windslabs ran naturally last Tuesday and were able to "step down" into deeper layers below. Watch for sculpted or stiff wind board on the windward aspects and rippled, chalky or hollow feeling/sounding pillows and drifts on steep leeward aspects. You should also be aware that due to the moderate to high winds last week, some of the older wind slabs may be found well below the ridgelines on leeward terrain. Practice safe travel protocols, and expose only one person at a time in wind loaded avalanche terrain.

advisory discussion

Join us this Friday and Saturday: Learn to recognize & avoid obvious avalanche hazards while traveling in the backcountry. This is a great way to get ready for a Level 1 Avalanche Class. Classroom session will be held at the McCall Ranger District Office at 6pm on January 6.  No registration needed for Classroom session, pre-registration for Field Session is required.  Contact: Forecast@payetteavalanche.org for more info.

Course content includes:

  • Avalanche statistics and human factors
  •  Avalanche terminology
  • Avalanche terrain
  • Snow pack and weather factors
  • Obvious clues and red flags
  • Trip Planning and Preparation 
  • Avalanche bulletins
  • Simple decision tools  
  • Travel protocols
  • Companion recovery

This is a two part class that includes a 2 hour classroom session with a 4-5 hour field session.  Attendance at the classroom session is required for participation at field session. Field sessions will be held at the Upper Elevation Snowmobile Lot for snowmobilers and near Brundage Mt Ski Area for the skiers. Suggested donation to the Friends of the Payette Avalanche Center for Classroom Session is $10, Field Session $20

Event Date: Friday, January 6, 2017 Classroom session & Saturday, January 7, 2017 Field session

Did you know: Only a small portion of our operating budget comes from the Forest Service, we RELY on the the Friends of  the Payette Avalanche Center to help finance the forecasts that you use and the equipment we use to gather the information.  Our forecast sleds are overdue for replacement and we rely on these as important tools to provide reliable avalanche advisories to the public...don't let your local avalanche center end up with a pile of melted metal, plastic, and rubber on the side of the road! Come out and support your FRIENDS and get involved, or make a tax deductible donation online.

recent observations

No new natural or human caused avalanches have been reported. 

On West Mountain via access gates at Tamarack on Monday, we found cold low density snow, and some shallow wind slabs on exposed wind affected terrain. We dug a pit on a northeast facing aspect at 7500 feet. What we found was a fairly right side up snowpack, with the main concern being the 10 cm of rounding basal facets at the ground. The surface that these grains were resting on, had a direct correlation to how stable it was. Where the snowpack was thinner and/or had large rocks, it failed easier in compression tests. Where the snowpack rested on grass, it was difficult/hard to initiate failure. 

As we mentioned around Christmas, this is a low probability/high consequence scenario if you were to trigger an avalanche to the ground on this layer. Fortunately for us, in most places, these facets are buried under over a meter of snow which helps spread the stress bubble of a skier or snowmobiler. 

 

Exposing rounding faceted snow grains below melt freeze crust 10 cm from the ground.

Fist full of facets that caused an easy (CT 9) failure during compression test. Next test column over it was hard to initiate failure (CT 24). Spatial variability at it's finest.

weather

No new snow was picked up overnight. Moderate North East winds continue to work over the high country this morning. Temperatures last night dipped to around 12 degrees in the upper elevations. The sky will favor clouds and  light snow today with a high temperature of 20 in the upper elevations, and 17 in Long Valley. Tonight we will  see a low of -14 in Long Valley, and -5 in the upper elevations...winds will pick up this evening creating a formidable wind chill factor of almost -30 degrees for tonight and tomorrow! Sunday will see the arrival of a warm front, harboring with it what looks to be a good amount of precipitation. 

 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: A 30 percent chance of snow. Cloudy, with a high near 20. East northeast wind 5 to 7 mph. New snow accumulation of less than a half inch possible. A 20 percent chance of snow. Mostly cloudy, then gradually becoming mostly clear, with a low around -14. Wind chill values between -17 and -27. Northeast wind 5 to 8 mph Sunny, with a high near 16. Wind chill values between -18 and -28. Northeast wind 5 to 7 mph becoming calm in the morning.
Temperatures: High 20 deg. F. Low -14 deg. F. High 16 deg. F.
Wind direction: East-northeast Northeast East-northeast
Wind speed: 5-7 5-8 5 to 7-calm
Expected snowfall: less than one half in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: A 30 percent chance of snow, mainly after 11am. Areas of blowing snow after 11am. Cloudy, with a high near 17. Wind chill values between -8 and -18. East northeast wind 11 to 16 mph. New snow accumulation of less than a half inch possible. Partly cloudy, with a low around -5. Wind chill values between -18 and -25. East northeast wind 13 to 17 mph. Sunny, with a high near 15. Wind chill values between -11 and -21. East northeast wind 6 to 11 mph becoming light and variable.
Temperatures: High 17 deg. F. Low -5 deg. F. High 15 deg. F.
Wind direction: East-northeast East-northeast East-northeast
Wind speed: 11-16 13-17 6-11 becoming light and variable
Expected snowfall: Less than one half in. 0 in. 0 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Payette National Forest and the Friends of 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.