THIS AVALANCHE ADVISORY EXPIRED ON January 4, 2017 @ 6:26 am
Avalanche Advisory published on January 3, 2017 @ 6:26 am
Issued by -
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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 ?
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
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  • Size ?
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Winds were light yesterday, but 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

Friends of the Payette Avalanche Center needs YOU! Come join us on TONIGHT at Idaho First Bank in McCall at 6 pm for an annual membership meeting. This meeting is open to the entire snow loving community,  and we need to hear from you on how the Payette Avalanche Center should grow into the future.

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 Tuesday night or make a tax deductible donation online.

recent observations

No new natural or human caused avalanches have been reported. 

My touring partner and I toured West Mountain via access gates at Tamarack yesterday. 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 snowpack, with my only 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

The mountains around the advisory area picked up a trace to 2 inches of new snow overnight, and 5 to 8 in the last two days. Overnight temps were in the single digits up high, and in the low teens in the valley. Today expect to see cloudy skies with an occasional flurry with a trace to 1 inch of total new snow accumulation. There is a major storm currently impacting the northern California and Oregon, but models look as though it is going to slide through southern Idaho and miss the West Central Mountains. A ridge of high pressure builds over the area on Thursday, bringing with it more cold temps. 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.
  Tuesday Tuesday Night Wednesday
Weather: Isolated snow showers before 11am. Areas of fog before 11am. Otherwise, mostly cloudy, with a high near 19. Wind chill values between -6 and 4. Light and variable wind. Chance of precipitation is 20%. A 20 percent chance of snow after 11pm. Cloudy, with a low around 4. Wind chill values between -5 and zero. Calm wind becoming northeast around 6 mph in the evening. A 20 percent chance of snow after 11am. Mostly cloudy, with a high near 18. Wind chill values between -2 and 8. East northeast wind 5 to 8 mph.
Temperatures: High 19 deg. F. Low 4 deg. F. High 18 deg. F.
Wind direction: Variable Northeast East-northeast
Wind speed: light 6 5 to 8
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Scattered snow showers before 11am. Mostly cloudy, with a high near 14. Wind chill values between -4 and 6. South wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 30%. Total daytime snow accumulation of less than a half inch possible. A 20 percent chance of snow after 11pm. Mostly cloudy, with a low around 6. Wind chill values between -5 and zero. Calm wind becoming east northeast 5 to 8 mph in the evening. A 20 percent chance of snow. Mostly cloudy, with a high near 17. Wind chill values between -1 and 7. East northeast wind 7 to 10 mph.
Temperatures: High 14 deg. F. Low 6 deg. F. High 17 deg. F.
Wind direction: South East-northeast East-northeast
Wind speed: 6 5 to 8 7 to 10
Expected snowfall: Less than .5 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.