THIS AVALANCHE ADVISORY EXPIRED ON March 5, 2018 @ 7:00 am
Avalanche Advisory published on March 4, 2018 @ 7:00 am
Issued by Jess Asmussen - Payette Avalanche Center
bottom line

Human triggered avalanches are possible at all elevations. Pockets of areas where human triggered avalanches are likely exist at upper elevations due to wind slabs that formed during and after the last storm cycle. These avalanches may occur on isolated terrain features where recent snow has loaded and they may be large enough to bury a person. Yesterday, a human triggered avalanche north of Brundage Ski Area demonstrated that the snowpack is still highly variable and sensitive to human triggers. 

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

Wind slabs that formed during the last storm are still lingering near ridges, in cross-loaded gullies, and in exposed areas. The most sensitive wind slabs exist on north to east facing terrain. Drifted snow, cornices above slopes, and shooting cracks can help to identify where these wind slabs exist. Significant cornice growth has occurred in many of these areas. Corniced ridges should be approached with caution as they often break off further from the edge than expected. 

 

advisory discussion

Conditions are variable across the forecast area right now. Our advisory is based upon a small number of observations. Please let us know what you are seeing out there whether it is deep stable snow or avalanche activity. Observations can be submitted here. The next avalanche advisory will be published March 9th. 

recent observations

A human-triggered avalanche just north of Brundage Ski Area yesterday (see picture below) demonstrated that there are still lingering instabilities and variability in the snowpack. This incident serves as a reminder that human triggered avalanches are still possible. Luckily, the skier was not caught in the avalanche. Near Tamarack and Brundage Ski Areas, multiple users were accessing the backcountry via the ski area in the last couple days. Although “side country” terrain is very close to ski area boundaries, these areas have not undergone avalanche control, and should be treated like other backcountry areas. Proper equipment, prudent terrain management, and one person at a time protocols are still very important.

During a tour yesterday in the Brundage backcountry, we were able to find evidence of wind loading at the upper elevations. Cornice size has increased significantly in the last week. Snow stability tests on a north aspect revealed a weak layer from the superbowl crust 40 cm from the surface. This layer failed in compression tests (CT22) but did not propogate during extended column tests (ECTN19).

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 8 deg. F.
Max. temperature in the last 24 hours: 18 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 3 mph
Maximum wind gust in the last 24 hours: 12 mph
New snowfall in the last 24 hours: Trace inches
Total snow depth: 65 inches
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.