THIS AVALANCHE ADVISORY EXPIRED ON December 23, 2016 @ 7:23 am
Avalanche Advisory published on December 22, 2016 @ 7:23 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The avalanche danger is Moderate above 6,000 feet. Below 6,000 feet, the avalanche danger is Low. Wind Slabs near ridgetops, and a widespread buried weak layer of facets on a crust near the bottom of the snowpack has a 5 foot slab resting on it.

How to read the advisory


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

Near the ground, within the first foot of snow, we have a couple crusts that are surrounded by facets that are rounding slowly. Our stability tests were giving moderate results that indicate a Low probability/High Consequence...a snomobile sidehilling would have the highest probability of triggering this layer, and especially greater probability in shallower areas. This weak layer has 145 cm (almost 5 feet) of snow on top of it. Be careful in avalanche terrian. Use safe travel protocols spread out, and only expose one person at a time. As we get moresnow on top of this layer, we may see more tender conditions, and avalanche danger rise?

Avalanche Problem 2: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Mid week, we saw wind slabs form on North and Nothwest aspects due to strong to intense SSW winds. This weeks wind slabs seem to be healing fast. Older wind slabs from recent North wids have slowly stiffened and become harder to trigger, but are still present. 

To travel safely today, it is going to be important to keep your eyes out for obvious signs of wind loaded slopes. Be on the lookout for wind scouring and loading (lens shaped slabs), keep an eye out for cracking of surface snow, and make terrain decisions that (in a worst case scenario) would not cause you to be taken over cliffs or into a terrain trap.

advisory discussion

We have a number of great beginner avalanche classes coming up. Be sure to check out 'local classes' under the Education tab at the top of the forecast page. If already have the basics down and are ready to take your Level One, do it. Make staying safe while playing in avalanche terrain a New Year's Resolution!

 

***Also, we apologize for the recent number of e-mails that people may be receiving from us due to our sever error, we hope to have this fixed soon.

recent observations

Yesteray, we toured above Twin Lakes on the North side of Granite, and found some shallow wind slabs that were getting harder to trigger...most alarming was the buried weak layer near the ground, within the first foot of snow, we have a couple crusts that are surrounded by facets that are rounding slowly. Our stability tests were giving moderate results that indicate a Low probability/High Consequence...a snomobile sidehilling would have the highest probability of triggering this layer, and especially greater probability in shallower areas. This weak layer has 145 cm (almost 5 feet) of snow on top of it. Be careful in avalanche terrian. Use safe travel protocols spread out, and only expose one person at a time. As we get more snow on top of this layer, we may see more tender conditions, and avalanche danger rise?

 

weather

An inversion is in effect. Today, we will see a high temperature in the upper elevations of 21 degrees, and a High temperature in McCall of 15 degrees. We wil also see increasing clouds and light south winds today before our next significant weather system that will impact the PAC advisory area Friday night into Saturday.

 

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Thursday Thursday Night Friday
Weather: Areas of dense fog before 11am. Otherwise, partly sunny, with a high near 15. Wind chill values between -2 and -12. South wind 3 to 5 mph. A 20 percent chance of snow after 11pm. Cloudy, with a low around 2. Wind chill values between -3 and -8. South southeast wind 3 to 5 mph. Snow. High near 24. Wind chill values between -6 and 4. South wind 5 to 7 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 3 inches possible
Temperatures: High 15 deg. F. Low 2 deg. F. High 24 deg. F.
Wind direction: South South-South East South
Wind speed: 3-5Mph 3-5 Mph 5-7Mph
Expected snowfall: 0 in. 0 in. 1-3 in.
Granite Mountain at 7700 feet.
  Thursday Thursday Night Friday
Weather: Increasing clouds, with a high near 21. Wind chill values between -8 and -18. Breezy, with a south southwest wind 14 to 21 mph. A 20 percent chance of snow after 11pm. Cloudy, with a low around 12. Wind chill values between -4 and 4. South southwest wind 13 to 16 mph. Snow. High near 24. Wind chill values between -5 and 5. Breezy, with a south wind 18 to 24 mph, with gusts as high as 33 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible.
Temperatures: High 21 deg. F. Low 12 deg. F. High 24 deg. F.
Wind direction: South-Southwest South-Southwest South
Wind speed: 14-21 13-16 18-24 Gusting to 33
Expected snowfall: 0 in. 0 in. 3-5 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.