THIS AVALANCHE ADVISORY EXPIRED ON January 10, 2020 @ 6:10 pm
Avalanche Advisory published on January 9, 2020 @ 6:10 pm
Issued by Eric Morgan - Idaho Panhandle Avalanche Center

Selkirks/Cabinets

bottom line

Snowfall starting Friday morning and continuing through Monday will be heavy and rapid which will increase avalanche danger throughout the forecast area.  

How to read the advisory

Selkirks/Cabinets

How to read the advisory

Snowfall starting Friday morning and continuing through Monday will be heavy and rapid which will increase avalanche danger throughout the forecast area.  

3. Considerable

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

3. Considerable

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

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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Over a foot of more dense recent storm snow from this weeks storm that is soft on top.  This sits ontop of a 2 cm ice crust noted in last weeks forecast.  The past few days has allowed some bonding and consolidation in the snowpack.  However with another few rounds of intense heavy snowfall the avalanche danger again will be on the rise with rapid and intense accumulations ontop of the current fluffy surface.   

Avalanche Problem 2: Wind Slab
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Dense windslabs exist on extreme upper ridgetops on Easterly aspects.  These areas have been releasing naturally during the intense snowfall and winds we experienced earlier in the week.  There is alot of evidence of natural avalanches and crowns in the backcountry from earlier in the week.  If other similar slopes that did not release naturally are disturbed there is a high likelyhood of triggering an avalanche.

Avalanche Problem 3: Persistent Slab
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About 2.5 feet below the current snow surface I found a layer of surface hoar that did not go on a compression tap test but did go when I tapped the column from the side (unofficially known as the IPAC side whammer).  I believe this layer did not fail on the compression tap test due to the 2 cm ice crust that was about 8 inches above it which acted as a small bridge.  I would not have any faith in this bridge and would be very cautious with human triggering and increased stress from expect snow accumulations throughout the outlook period.

advisory discussion

Today I would just like to emphasize that the hazard rating of considerable means dangerous avalanche conditions exist requiring careful snowpack evaluation, cautious route finding and conservative decision making is essential.   Natural avalanches possible and human triggered likely.  Open slopes greater than 30 will be the slopes that should shout to watch out.  

recent observations
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On Blue Mountain in the Selkirks I found 185 cm of snow that is consolidating with numerous crusts, atleast one surface hoar layer and basal facets (weak sugarlike and hollow snow crystals) near the ground.  The pack is slowly trying to stabilize some of these layers but more time is needed and we have more rapid change coming atop this snowpack to escalate danger.  Natural avalanche activity from the height of this weeks storm was evident on all steep open windloaded slopes looking to the north toward Mt. Casey.  The avalanches propogated a long ways and into the vegetation adjacent.  The avalanches mostly included the fresh storm slabs and I did not see any sign of larger blocks from the previous snowpack.  

Weather and CURRENT CONDITIONS
weather summary

Snow throughout the weekend and into Monday.   Winds 20-25 gust to 36.  About 3 feet snow total through sunday.  Temperatures mid 20s and dropping to single digits by sunday evening.   

Weather observations from the Region
0600 temperature: 11 deg. F.
Max. temperature in the last 24 hours: 20 deg. F.
Average wind direction during the last 24 hours: 270
Average wind speed during the last 24 hours: 0-10 mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: 96 inches
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.