THIS AVALANCHE ADVISORY EXPIRED ON December 28, 2016 @ 6:45 am
Avalanche Advisory published on December 27, 2016 @ 6:45 am
Issued by -
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The avalanche danger will start out MODERATE this morning in elevations over 6,000 feet. However, with snow currently falling and forecasted winds to blow into the 20 and 30 mph range, human caused avalanches will become likely in wind loaded terrain and the avalanche danger will rise to CONSIDERABLE above 7,000 feet by early afternoon. 

Below 6,000 feet generally safe avalanche conditions exist and 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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Most of the wind slabs that formed during our pre-Christmas storm have settled out to a large degree and won't be nearly as sensitive today. However, just as one batch of wind slabs are healing, another round of wind slabs will be forming due to today's storm. Winds are forecasted to blow 20 to 30 mph out of the west southwest, and with new snow available for transport, there will be a fresh new batch of slabs forming throughout the day. Once these new slabs start to develop, they will be sensitive to trigger and in the small to medium size range. Also keep in mind, a fresh wind slab avalanche has the potential to 'step down' into older layers of snow causing for an avalanche that has the possibility of being several feet deep.

Be sure if you are traveling into steep committing avalanche terrain, to find some test slopes and/or dig a few quick holes to see how the snowpack is adjusting to the new snow and wind.

 

Avalanche Problem 2: Persistent Slab
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We have found a weak layer near the ground throughout the advisory area over the last two weeks that is made up of weak faceted snow or a combination of facets and old crusts left over from our early season snowpack.  The weak layer of facets is fairly widespread and well developed in the upper elevations especially on the shadier aspects where early snowfall accumulated. Shallow rocky areas are also harboring this layer on other aspects.  George described this problem last week as a low probability/ high consequence avalanche problem...meaning you are not very likely to trigger a slide this deep but the consequences if you did would be bad.  The 3-5 foot overlying slab is gaining strength which is good but is also turning into more of a hard, consolidated slab if it fails. Now is a good time to play it safe on steep shady slopes or slopes with thinner/rocky areas where you are more likely to trigger the weak layer.  

This kind of problem is both difficult to trigger and more difficult to predict.  Slopes with tracks on them are not a good indicator of stability as the trigger points are likely to be isolated to thin or weak spots that are hard to find or easy to miss.  Remember that a lack of red flags or signs of instabilities is not a good indicator for a deep or persistent slab problem.  Don't let the lack of evidence lull you into more consequential terrain or sloppy group management.  Use good travel techniques(one at a time) and watch your partners if you are riding or sliding in this type of terrain.

Avalanche Problem 3: Storm Slab
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If traveling in avalanche terrain that has not seen the affects of wind, there is a possibility of triggering a soft storm slab. However, with the forecasted winds today, these will be in very isolated areas. That is why I have assigned this as Avalanche Problem #3. Keep storm slabs in your thoughts as you make terrain decisions today, but wind slabs will definitely be my main concern.

advisory discussion

Don't forget about our 'Know Before You Go' class TONIGHT at the McCall Ranger District at 6 pm. KBYG is a great first step or a quick review if you are planning on heading into the backcountry and want to stay safe.  If you are ready to take the next step after KBYG, PAC still has room for both skiers and snowmobilers in our upcoming Intro to Avalanches class on Jan 6 and 7, registration by email is required.

Friends of the Payette Avalanche Center needs YOU! Come join us on Tuesday January 3rd 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 Payette Avalanche Center to help finance the forecasts that you use. Please come out and have your voice be heard and show your support!

recent observations

No new human or natural avalanches have been reported.

Remember, your information can save lives. If you see anything we should know about, please participate in the creation of our own community avalanche advisory by submitting snow and avalanche conditions. You can email the forecasters directly at forecast@payetteavalanche.org

 

weather

Overnight lows in the mountains of the PAC advisory area were in the teens, with winds blowing in the 20's and gusting into the 30's out of the south southwest. A winter weather advisory has been issued for the West Central Mountains for the next 24 hours. A forecasted .6 to 1 inch of snow water equivalent is expected to impact the advisory area by tomorrow morning, with snow totals equiling 6 to 14 inches. Winds associated with this storm will be out of the west southwest, blowing in the 20's and gusting into the 30's.  We will see a clearing off of precip Wednesday afternoon into Thursday, with the next chance for measurable snowfall coming on Friday.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow. High near 21. South wind around 8 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 2 to 4 inches possible. Snow. Low around 14. South wind around 6 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible. A 30 percent chance of snow before 11am. Mostly cloudy, with a temperature rising to near 23 by 10am, then falling to around 9 during the remainder of the day. Calm wind becoming south southwest around 5 mph in the afternoon. New snow accumulation of less than a half inch possible.
Temperatures: High 21 deg. F. Low 14 deg. F. High 23 then falling deg. F.
Wind direction: South South South southwest
Wind speed: 8 6 5
Expected snowfall: 2 to 4 in. 1 to 2 in. Less than .5 in.
Granite Mountain at 7700 feet.
  Tuesday Tuesday Night Wednesday
Weather: Snow. High near 20. Wind chill values between zero and 5. Breezy, with a west southwest wind around 24 mph, with gusts as high as 33 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 3 to 7 inches possible. Snow. Low around 12. Wind chill values between -4 and 3. West wind 14 to 18 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. A 40 percent chance of snow before 11am. Mostly cloudy, with a high near 18. Wind chill values between -4 and 6. West wind 8 to 15 mph. New snow accumulation of less than a half inch possible.
Temperatures: High 20 deg. F. Low 12 deg. F. High 18 deg. F.
Wind direction: West southwest West West
Wind speed: 24 gusting 33 14 to 18 8 to 15
Expected snowfall: 3 to 7 in. 2 to 4 in. Less than .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.