THIS AVALANCHE ADVISORY EXPIRED ON December 25, 2017 @ 6:47 am
Avalanche Advisory published on December 24, 2017 @ 6:47 am
Issued by Dave Bingaman - Payette Avalanche Center
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The primary avalanche hazard today will be found on upper elevation slopes where small,  wind slabs have formed through out the last week.  A layer of weak, faceted snow below the recent storm snow and above the Thanksgiving rain crust will also be a layer to watch as we add an additional snow load over the next few days. Buried treasure is abundant, and easy to locate, ski and ride with caution!  

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
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Small isolated wind slabs were found Friday near Twin Lakes on Granite Mountain on northerly ridgelines, and Saturday in the lick Creek drainage.  These slabs were shallow ( 4-6 inches), sensitive to ski cuts but lacked the ability to propagate beyond our skis Friday. Yesterday, in the Lick Creek drainage, the wind slabs were not sensitive, and stayed put. Evidence of mid-storm natural soft wind slab avalanches were dotted around on East and NE facing steep terrain. The effects of the high winds earlier in the week were pretty obvious as well with spines and tree wells growing on ridges and sub ridges above 7000 feet.  Payette Powder Guides reported several obvious crowns on Beaverdam Peak and 8302  that had failed naturally mid slope in steep terrain following the Tuesday/Wednesday storm event.

 

Avalanche Problem 2: Persistent Slab
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There is a layer of rounding, faceted snow below the most recent storm snow,  we found this layer to be somewhat reactive as we tested for it throughout the day in hasty pits and quick shear tests.  In compression it produced low energy, non planar failures in the CT 21-25 range due to the lack of a cohesive slab above it.  We don't have enough data yet to know exactly how wide spread this layer is but we found it on multiple aspects and at multiple elevations in the Goose Lake Area, and in the Lick Creek drainage yesterday.

In addition to the upper layer of rounding, faceted snow there is a significant weak layer of faceted snow above the Thanksgiving rain crust.  Similar to the upper layer, this layer lacks a cohesive, overlying slab to create a significant avalanche problem right now.  As we add more load in the form of additional snowfall or wind loading, this layer will likely become a significant avalanche problem.  Like the upper layer, it is a widespread layer across multiple aspects and elevations.  

advisory discussion

The PAC will only be operating 3 days per week this year.  Your observations are more important now than ever before, please let us know what you are seeing while you are out riding or skiing in the local backcountry.  It's super easy to send us info and photos with date, location, pictures, general or specific snow observations, just click on the submit observations page on the PAC website and add what you saw or found in the snow.  You can also email the forecasters directly at:  forecast@payetteavalanche.org

recent observations

Yesterday, in the Lick Creek drainage, we observed just under 5 feet of snow at 6700 feet on a North aspect, with 10 inches of new snow that fell overnight making for about 20 inches of blower powder that made travel on flatter slopes more difficult.  The coverage is not to be trusted with the upper 2 feet in the snowpack not padding or covering, but hiding obstacles that lie beneath the snow, we were threading the needle between rocks and downed trees and bushes...another week or 2 of snow and settlement should help make travel much more enjoyable and safe

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The coverage looking better above 7,000 feet 

Natural, 10" thick, soft wind slab that had pulled out within the new snow Friday night towards the end of the storm.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: N/A deg. F.
Max. temperature in the last 24 hours: deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours: mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: inches
Total snow depth: inches
weather

Our Granite station is still offline for the short term, we will be making our way up to it in the next two weeks.  

NWS forecast discussion for SW Idaho:

.SHORT TERM...Today through Sunday...Snow continues this morning
in southern Idaho along a southward moving cold front. So far,
snow and QPF have exceeded forecasts in the Upper Treasure Valley
from Boise through Mountain Home, with up to 5 inches new snow
in spots. However, the majority of the area will stay under 4
inches total, even with another 1-2 inches expected today, so
will stay with the winter weather advisory rather than upgrade
to winter storm warning. Snow has decreased as of 3 AM MST, but
models show a resurgence around sunrise, then ending from north
to south through the day. There has been fog tonight in the
Western Magic Valley, but increasing west winds should disperse
the fog before sunrise. Later today colder and drier air will
come in from the north, and gusty northwest winds will make it
feel colder. Clearing skies with diminishing winds, and a new
snow cover will result in a very cold night, with lows 10 below
to 10 above zero in the mountains, and 10 to 20 above in the
valleys. Sunday will bring increasing clouds as today`s frontal
boundary turns back north and east over our area. The front will
ride over the very cold air at low levels resulting in light
snow in eastern Oregon Sunday, spreading into southwest Idaho
Sunday afternoon and especially Sunday night, with further
accumulations.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: A 20 percent chance of snow after 11am. Increasing clouds, with a high near 18. Calm wind. Snow. Low around 15. Calm wind becoming south around 5 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. A 50 percent chance of snow. Cloudy, with a high near 26. Light and variable wind becoming south around 5 mph in the morning. New snow accumulation of around an inch possible.
Temperatures: 18 deg. F. 15 deg. F. 26 deg. F.
Wind direction: Calm South South
Wind speed: 0 5 mph 5 mph
Expected snowfall: o in. 2-4 in. 1 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: A 30 percent chance of snow after 11am. Increasing clouds, with a high near 18. Wind chill values between -2 and 5. Southwest wind 8 to 10 mph. Total daytime snow accumulation of less than one inch possible. Snow. Temperature rising to around 22 by 3am. West southwest wind 7 to 10 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. Snow likely. Cloudy, with a temperature falling to around 13 by noon. West wind 5 to 11 mph. Chance of precipitation is 60%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 4 deg. F. 22 deg. F. 13 deg. F.
Wind direction: SW WSW W
Wind speed: 5-10 7-10 5-11
Expected snowfall: less than 1 in. 2-4 in. 1-3 in.
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.