THIS AVALANCHE ADVISORY EXPIRED ON January 19, 2018 @ 8:58 pm
Avalanche Advisory published on January 18, 2018 @ 8:58 pm
Issued by Eric Morgan - Idaho Panhandle Avalanche Center

Selkirks/Cabinets
St. Regis Basin/Silver Valley

bottom line

Significant windloading and recent snowfall from yesterday mornings storm has formed deep windslabs near ridgetops on N, NE, and E aspects near 6000 foot range.  This has increased the load on buried surface hoar about 2 feet down (deeper in windloaded areas).  With the recent snowfall and warmer temperatures yesterday wind slab avalanches will become more reactive to human triggers.  Cautious route finding is key in our current snowpack state.   

How to read the advisory

Selkirks/Cabinets
St. Regis Basin/Silver Valley

How to read the advisory

Significant windloading and recent snowfall from yesterday mornings storm has formed deep windslabs near ridgetops on N, NE, and E aspects near 6000 foot range.  This has increased the load on buried surface hoar about 2 feet down (deeper in windloaded areas).  With the recent snowfall and warmer temperatures yesterday wind slab avalanches will become more reactive to human triggers.  Cautious route finding is key in our current snowpack state.   

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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The winds associated with yesterdays snow has caused significant loading on North and East aspects which have already been experiencing natural releases earlier in the week due to buried surface hoar in the upper 2 feet of the snowpack.  These slabs are sensitive to human triggering as some settling has occured since the natural avalanche cycle.  Watch for these areas near open ridgetops in the 6000 foot elevation range.  

Avalanche Problem 2: Storm Slab
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Buried surface hoar is now well protected from new storm snow further keeping it in tact in upper elevations where rain did not occur.  Mid and lower elevations experienced rain which percolated down to our upper surface hoar in the upper pack.  However there are still deeper persistent weak layer of surface hoar and facets within the pack that may need some time to heal with the heavy snow on top due to yesterdays rain.  Temperatures are expected to cool near and below the freezing level through the weekend helping things out in the mid elevations.

Avalanche Problem 3: Loose Wet
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With lower elevations above freezing through the weekend, steep slopes could experience loose wet slides due to the recent rain on snow event and continued high temperatures increasing the load on weaker layers in the lower pack.   Theses slides are generally small and slow moving, but could be large enough to bury you in a terrain trap or long running terrain.

recent observations

Near Lunch Peak yesterday we saw some evidence of natural releases from sometime earlier in the week.  We found 2 meters of snowpack on a NW aspect with buried surface hoar 2 feet down.  Our extended column test did not react however with a little more force after the test it did fully propogate on the surface hoar layer.  This is where things get tricky as we know this touchy layer is out there, some places it goes easy and some it takes a little more forceful trigger.  The likelyhood is less than earlier in the week but very high consequece if you trigger this layer.  With the triggering of this layer, it could step down and trigger deeper surface hoar, facets down to the Thanksgiving crust 5 feet plus deep.  Keep in mind that we have been high 3 times this year....more than most years in North Idaho, we typically have a forgiving snowpack, but the dynamics and structure are not the norm and pose a greater threat than we are used to.  We have some small storms pulsing through this weekend coming in 1-3 inch increments that should make the surface conditions better for recreating on.  Keep in mind the dynamic pack and choose your routes wisely.  Be safe and enjoy!

All snotel site in the forecast area from lookout north are showing 9 inches of snow with temperatures at 26 with moderate winds near ridgetops.

Weather and CURRENT CONDITIONS
weather summary
Today
A chance of snow showers before 10am, then a chance of snow after 10am. Cloudy, with a high near 28. Southwest wind around 11 mph. Chance of precipitation is 50%. Total daytime snow accumulation of around an inch possible.
Tonight
Snow likely. Cloudy, with a low around 24. Southwest wind 10 to 13 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Saturday
Snow likely before 10am, then snow showers after 10am. High near 28. Southwest wind around 11 mph. Chance of precipitation is 80%. New snow accumulation of around an inch possible.
Saturday Night
A 30 percent chance of snow showers, mainly before 4am. Cloudy, with a low around 24. Southwest wind around 10 mph. New snow accumulation of less than a half inch possible.
Sunday
Snow, mainly after 4pm. High near 30. South wind 10 to 14 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible.
Weather observations from the Region
0600 temperature: 26 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: 270
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: 9 inches
Total snow depth: 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.