THIS AVALANCHE ADVISORY EXPIRED ON December 24, 2017 @ 7:02 am
Avalanche Advisory published on December 23, 2017 @ 7:02 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, sensitive 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 more snow and additional 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 yesterday near Twin Lakes on Granite Mountain on northerly slopes.  We have also had reports of similar thin slabs from the Lick Creek and Big Creek areas. These slabs were shallow ( 4-6 inches), sensitive to ski cuts but lacked the abilty to propagate beyond our skis yesterday. 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 Thursday that had failed naturally mid slope in steep terrain following the Tuesday/Wednesday stom 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 yesterday on multiple aspects and at multiple elevations in the Goose Lake Area

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

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.
  Saturday Saturday Night Sunday
Weather: Scattered snow showers before 11am. Cloudy through mid morning, then gradual clearing, with a temperature falling to around 10 by 5pm. Light west northwest wind becoming northwest 6 to 11 mph in the morning. Chance of precipitation is 30%. Total daytime snow accumulation of less than a half inch possible. Mostly clear, with a low around -3. Light and variable wind. A 30 percent chance of snow after 11am. Increasing clouds, with a high near 17. Calm wind. New snow accumulation of less than one inch possible.
Temperatures: 10 deg. F. -3 deg. F. 17 deg. F.
Wind direction: W/NW Variable Calm
Wind speed: 6-11 Light Calm
Expected snowfall: Trace in. 0 in. less than 1 in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Scattered snow showers before 11am. Mostly cloudy, then gradually becoming sunny, with a temperature falling to around 4 by noon. Wind chill values between -4 and -14. North northwest wind 7 to 15 mph. Chance of precipitation is 30%. Total daytime snow accumulation of less than a half inch possible. Mostly clear, with a low around 3. Wind chill values between -4 and -12. West northwest wind 7 to 11 mph. A 30 percent chance of snow after 11am. Increasing clouds, with a high near 17. Wind chill values between -2 and 5. South southwest wind 8 to 10 mph. New snow accumulation of less than one inch possible.
Temperatures: 4 deg. F. 3 deg. F. 17 deg. F.
Wind direction: NW W/NW SW
Wind speed: 7-15 7-11 8-10
Expected snowfall: Trace in. 0 in. less than 1 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.