THIS AVALANCHE ADVISORY EXPIRED ON January 19, 2019 @ 7:02 am
Avalanche Advisory published on January 18, 2019 @ 7:02 am
Issued by Melissa Hendrickson - Idaho Panhandle Avalanche Center

Selkirks/Cabinets
St. Regis Basin/Silver Valley

bottom line

Mid-week's weather left us with a snowpack with a bed surface of crust and surface hoar.  The new storm is falling on this weak, slippery layer and will cause the avalanche danger to increase through the weekend as more snow accumulates.  Expect to find reactive storm slabs at all elevations. Watch for indication of these in the flat areas with shooting cracks and whumphing.  

How to read the advisory

Selkirks/Cabinets
St. Regis Basin/Silver Valley

How to read the advisory

Mid-week's weather left us with a snowpack with a bed surface of crust and surface hoar.  The new storm is falling on this weak, slippery layer and will cause the avalanche danger to increase through the weekend as more snow accumulates.  Expect to find reactive storm slabs at all elevations. Watch for indication of these in the flat areas with shooting cracks and whumphing.  

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.

3. Considerable

?

Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Storm Slab
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3" to 5" inches of new snow fell across the forecast region yesterday creating soft storm slabs.  In many locations this snow fell on top of well-developed weak surface hoar which had formed on top of a stout crust.  See the photo below for an example of the surface hoar we found on Wednesday before it got buried.  Pay attention as you are traveling for shooting cracks and whumphing. Expect this danger to increase as the weekend progresses and the storm slabs become thicker and more cohesive.  We saw surface hoar development at the low elevations, so make sure your avalanche game is dialed when you leave the trailhead.  Use smart route selection and traveling etiquette on your way into your riding or sliding areas; our trails pass by lots of road cuts that can create small slides with large consequences.  

Avalanche Problem 2: Persistent Slab
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We still have persistent slabs and deep slabs in many locations buried in our snowpack.  While as time passes it becomes more and more unlikely that these will be triggered by a rider or slider, they are still enough of a problem to warrent talking about every week.  Continue to use extra caution around areas with shallow snowpacks as that will be the most likely areas that will trigger these hidden dragons.  

recent observations

In the Silver Valley and the Selkirks/Cabinets this week there was widespread surface hoar on top of crust development from Fourth of July Pass (3121ft) up to around 6000ft in places.  As we were travelling yesterday, small soft slabs were easy to trigger on convex roll-overs and we saw shooting cracks.  Above 6000 ft we didn't find surface hoar (or crust) at our locations, but it is possible that it exists elsewhere that high.  Check your location by digging down and looking for sugary snow underneath our new storm slab.  With more snow forecasted, this danger is going to increase as more weight is added on top of this weak layer.  Dial back your terrain selection and pay close attention for red flags as you are traveling.  After having a snow drought, it will be nice to get out in powder again, but do it with avalanche safety in mind!

 

Weather and CURRENT CONDITIONS
weather summary

More wintery conditions will persist through the weekend with storms coming in that could bring an additional foot of snow by Sunday.  Winds will also increase from what we've been seeing so we have a recipe for wind slab development through the weekend as well.  

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.