THIS AVALANCHE ADVISORY EXPIRED ON December 29, 2018 @ 6:03 am
Avalanche Advisory published on December 28, 2018 @ 6:03 am
Issued by Jeff Thompson - Idaho Panhandle Avalanche Center

Kootenai
Selkirks/Cabinets
St. Regis Basin/Silver Valley

bottom line

The colder air temperature and minimal winds from the past couple days has kept the snow surface nice and fluffy! Even though the weather has been pretty stable, we're still seeing changes happen in the snowpack.  Current snow conditions (thick stiff slab of snow with light new snow on top) are making backcountry travel a little easier right now, so don't be tempted to travel in places your gut is telling you to stay off of.  

How to read the advisory

Kootenai
Selkirks/Cabinets
St. Regis Basin/Silver Valley

How to read the advisory

The colder air temperature and minimal winds from the past couple days has kept the snow surface nice and fluffy! Even though the weather has been pretty stable, we're still seeing changes happen in the snowpack.  Current snow conditions (thick stiff slab of snow with light new snow on top) are making backcountry travel a little easier right now, so don't be tempted to travel in places your gut is telling you to stay off of.  

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Persistent Slab
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A buried surface hoar layer midway (70ish cm down) is still the chief complaint in the snowpack. All the observations I've received over the past couple of days spoke this layer. It seems to be wide spread across all of our forecast zones. I'm describing this layer as 'laying dorment' right now. "laying dormant' isn't a good thing. Even though we're not seeing avalanche activity on this layer right now, it is very possible that it is woken up at some point. Generally it's a weather event that kicks the layer into gear but it can also be gravity over time adding stress to it. Long story short...don't completely trust it. We'll continue to monitor that layer and give out information as we see changes.

Avalanche Problem 2: Deep Slab
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As the snowpack stiffens in the cold temperatures, it's ability to transfer energy increases as well.  I've included basal facets in the forecast as a problem today. My feeling is that we are going to see some instabilities deep in the pack wake up. As the snowpack becomes stiff and strong the energy from a snowmobile or skier can transfer through the snowpack to instabilities at the bottom of the pack (basal facets or sugar snow) resulting in large avalanches. Sorry to add another problem to your decision making tool box but I think we've hit the point that we need think about deep instabilities again.

Avalanche Problem 3: Wind Slab
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Weather and CURRENT CONDITIONS
Weather observations from the Region
0600 temperature: 19 deg. F.
Max. temperature in the last 24 hours: 29 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 3-7 mph
Maximum wind gust in the last 24 hours: 21 mph
New snowfall in the last 24 hours: 1-4'' inches
Total snow depth: 170cm inches
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Snow / fog Snow Snow / rain
Temperatures: 29 deg. F. 27 deg. F. 38 deg. F.
Wind Direction: calm SW SW
Wind Speed: calm 3-5 5-9
Expected snowfall: >1'' in. >1'' in. 1-2'' in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Snow/fog Snow Snow
Temperatures: 20 deg. F. 17 deg. F. 32 deg. F.
Wind Direction: SW SW SW
Wind Speed: 10-12 8-16 18-22
Expected snowfall: 1-2'' in. 2-4'' in. 2-4'' in.
Disclaimer

Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit.  For a recorded version of the Avalanche Advisory call (208)765-7323.