THIS AVALANCHE ADVISORY EXPIRED ON December 21, 2019 @ 6:56 am
Avalanche Advisory published on December 20, 2019 @ 6:56 am
Issued by Jeff Thompson - Idaho Panhandle Avalanche Center

Selkirks/Cabinets

bottom line

Winter just got kicked into full gear! A strong winter storm arrived yesterday and continues to drop a big snow and rain on the Selkirk and Cabinet mountains. A large heavy snowload will put stress on the underlying weak layers in the snowpack. The snow/rain line looks to be at 4500'

How to read the advisory

Selkirks/Cabinets

How to read the advisory

Winter just got kicked into full gear! A strong winter storm arrived yesterday and continues to drop a big snow and rain on the Selkirk and Cabinet mountains. A large heavy snowload will put stress on the underlying weak layers in the snowpack. The snow/rain line looks to be at 4500'

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

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.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Storm Slab
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Up to 30+'' are forecasted to fall at upper elevations before this storm breaks. The new snow will be very prone to avalanching for the next 48 hours or so. This is the first significant snow storm for many of the areas in the forecast zone. This storm is producing a lot of wind and moisture, which will make the new snow firmer, heavier and more prone to becoming a slab, which will increase the likely hood for an avalanche. The rain/snow line was at 4500'

Avalanche Problem 2: Persistent Slab
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A moderately reactive buried surface hoar layer is a big concern with the arrival of new snow. The buried surface hoar layer will only be able to support so much weight before it fails. We will continue to monitor the buried problematic layer to see how the new snow effects it. Right now, I strongly recommend staying off of steep slopes near ridgelines, esspecially on leeward slopes.

Avalanche Problem 3: Loose Wet
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The rain/snow line was at 4500' or so over night. Areas in the rain are going to present a completly different avalanche problem then upper elevations, where it snowed. Wet surface snow can weaken the upper portion of the snowpack. Be aware of the possibility of wet and loose avalanches below 4500ft

Weather and CURRENT CONDITIONS
Weather observations from the Region
0600 temperature: 36 deg. F.
Max. temperature in the last 24 hours: 41 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 12 mph
Maximum wind gust in the last 24 hours: 28 mph
New snowfall in the last 24 hours: 4'' inches
Total snow depth: 95 cm inches
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Rain Rain Rain
Temperatures: 43 deg. F. 40 deg. F. 43 deg. F.
Wind Direction: SW SW SE
Wind Speed: 8-10 G 21 3-6 4-7
Expected snowfall: 0 in. 0 in. 0 in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Snow Snow Snow
Temperatures: 34 deg. F. 34 deg. F. 32 deg. F.
Wind Direction: S S S
Wind Speed: Very windy 25-45 G 50+ 30-35 24-28
Expected snowfall: 1-3'' in. 1-3'' 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.