THIS AVALANCHE ADVISORY EXPIRED ON December 28, 2019 @ 6:42 am
Avalanche Advisory published on December 27, 2019 @ 6:42 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

St. Regis Basin/Silver Valley

bottom line

Our main concern is still buried persistent weak layers that have the potential to slide to ground.  Areas where the ground surface is smooth, such as beargrass slopes, have a higher probablity of sliding if an avalanche is triggered. We expect to continue to see reactive persistent weak layers for a while with the weather pattern that we are experiencing. Bottom line is we have a thin and weak snowpack.

How to read the advisory

St. Regis Basin/Silver Valley

How to read the advisory

Our main concern is still buried persistent weak layers that have the potential to slide to ground.  Areas where the ground surface is smooth, such as beargrass slopes, have a higher probablity of sliding if an avalanche is triggered. We expect to continue to see reactive persistent weak layers for a while with the weather pattern that we are experiencing. Bottom line is we have a thin and weak snowpack.

2. Moderate

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

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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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The pineapple express that hit our region last weekend erased some of the persistent weak layers down low, but not up high.  Above 6000', buried surface hoar and basal facets are proving to be our persistent weak layer to end the year with.  These are more developed in some areas than others and the only way you will know if if you dig down. These persistent weak layers are more risky in areas greater than 35 degrees that have a smooth bed surface such as a forest floor or bear grass meadows.  The energy from the failure has a more likely chance of sliding on these surfaces. Avoid this risk by sticking to moderate terrain.   

Avalanche Problem 2: Wind Slab
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Now that the air temperature has cooled off again, the new snow we have seen is of much lighter density.  Expect windslabs on the NW -N-NE ridges and peaks.  While we haven't had much snow to create thick windslabs, these to have the potential to step down to our persistent weak layers to create an avalanche with much larger consequences.  

recent observations
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Yesterday we traveled in the Grouse Peak area and found variable snowpack depths and reactivity.  In areas with thinner pack of 60 to 70 cm (23-28 inches), we were punching through all the way to ground when we stepped on the snow surface in boots. This is a sign of instability.  Pit tests were still being very reactive, with full propegation in our extended column tests.  Those results, the spatial variability, and the shallow snowpack all have us being conservative.  If a small avalanche is triggered, it has big consequences right now.  Unfortunately, things are not going to change fast.  We are headed into a period of uneventful weather, which will help the snowpack strengthen, but it will take time.  

Thank you to everyone on Christmas break this week who is sending in observations!  The more observations we get from around the region, the safer we all are.  

 

 

Weather and CURRENT CONDITIONS
Two-Day Mountain Weather Forecast Produced in partnership with the Spokane NWS
For 2000 ft. to 4000 ft.
Friday Friday Night Saturday
Weather: Snow then Chance Snow Slight Chance Snow then Cloudy Slight Chance Snow
Temperatures: 28 deg. F. 22 deg. F. 31 deg. F.
Wind Direction: W Calm Variable
Wind Speed: 6 Light
Expected snowfall: 1-2 in. 0 in. 0 in.
For 4000 ft. to 6000 ft.
Friday Friday Night Saturday
Weather: Snow and Breezy Chance Snow Mostly Cloudy
Temperatures: 19 deg. F. 15 deg. F. 23 deg. F.
Wind Direction: SW W SW
Wind Speed: 18 8-14 8-10
Expected snowfall: 2-4 in. <1 in. 0 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.