Avalanche forecast

Southern Wallowas

Wallowa Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

To reduce your chances of triggering an avalanche, avoid areas that have been recently loaded by the wind.  It remains possible to trigger a larger avalanche in isolated areas that hold persistent weak layers up to 3 feet from the surface.  The characteristics of these areas include shallow (less than 4 feet) snowpack depth, rocky steep rollovers, and areas where weak snow has formed around a crust or buried surface hoar exists and a cohesive slab sits above the weak snow.  

This forecast is sponsored by CB Construction. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Isolated areas in the Northern Wallowas hold the potential to trigger a large avalanche failing on weak snow that sits under a slab.  Here is what I would recommend looking for to avoid this problem: 

    -Shallow snowpack areas (less than 4 feet of total snow).  Using your probe to determine snowpack height through your travels will give you a good idea of the changing snowpack depths across different aspects and elevations. 

    - Areas that harbor a stout crust with weak snow around the crust and a slab above.  Might have to bust out your shovel and look at the structure of the upper few feet of the snowpack.  If you see this type of snowpack structure, my advice would be to stick to terrain less than 30 degrees.  Check out the recent observation from the Chief Joseph area here. 

    -Avoid trigger points when in terrain greater than 35 degrees.  These include steep convex rollovers and rocky zones.  

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Monday's storm brought 4-6" of new snow with moderate to strong Northwest winds.  These winds redistributed the snow onto leeward aspects, but also stripped many upper start zones.  Look for patterns of wind loading and clues to wind-loaded slopes as you travel through the mountains today.  Visual clues include rounded and smooth-looking deposits of snow.  Look for corniced ridgelines and windward areas that are stripped of new snow.  It is likely that the wind has already transported most of the snow that is available but be on the lookout for newly forming slabs of snow with today's winds forecasted to be in the upper teens to 20's out of the Southwest. 

    (2/14/2023)

    Active wind loading during Monday's storm 

    Photo: cm

Avalanche Discussion

Overall, the snowpack in the Northern Wallowas looks to have better stability than we have seen so far this winter.   I spent the last couple of days traveling around the wing ridge area and was pleased to find a mostly right-side-up upper snowpack.  Many areas in the shady side of the compass are holding over 2 meters/6 feet of snow, and I was unable to find any buried surface hoar layers in the upper 3 feet of the snowpack.  The one layer of concern worth keeping an eye on is the January 24th Rime Crust which can be found just over a foot down from the surface.  This layer seems to exist in elevation bands of about 7500' and above.   There are some weaker, faceted grains that are just below this crust that produced some failures in snowpack tests, but no propagation in Extended Column Tests.  You can check out my observation from Monday here.  See the photos below for an example of the upper 4 feet of the snowpack on a North Aspect at 8k'.  The layers of buried surface hoar that we have been tracking for the last month or more seem to be less reactive if not unreactive as they continue to gain strength in the deepening snowpack.

Small Loose Dry avalanches on the shady half of the compass will be possible today in terrain steeper than 35 degrees.  Avoid riding in steep terrain that is above terrain traps to decrease your chances of getting hurt by a Loose Dry avalanche.  Small Loose Wet avalanches will also be possible in this steeper terrain when direct sun are on solar aspects.  The same travel advice applies.  Avoid riding steep terrain above terrain traps as the new snow loses cohesion from the warmth of the sun. 

If you hunt for it in the right places, you can still find poor structure in the snowpack.  I dug a snowpit at 7800' on an East aspect in a notoriously shallow snowpack location on the skier's right side of Phat ridge adjacent to South bowl and found myself wallowing in weak snow to the ground.  There was only 90 cm/3 feet of snow in this location.  See the photo below of weak and uncohesive sugar snow near the ground.  The good news is that there was no slab above the weak snow in this location.  No slab, no problem... but this is just one data point.   Yesterday, observers found poor structure in the snowpack on a Northeast aspect at 7300.  See the observation here. 

Here's the takehome as our snowpack continues to gain strength:  Avoid wind loaded terrain.  Use small inconsequential test slopes to test the reactivity of wind slabs using your skis or machine.  Where shallow snowpacks exist (less than 4 feet), it is important to avoid areas that hold a cohesive slab above sugar snow.  Avoid trigger points such as rocky convex rollovers with terrain steeper than 35 degrees.  Be aware of avalanche paths that may be connected to areas with shallower snowpacks.  Even in times of decreased avalanche hazard, continue to only expose one rider at a time to avalanche terrain, keep eyes on them, and regroup in safe locations out of the runout of any avalanche path.  

A big thanks to all of the ski guides from Wallowa Alpine Huts and Eagle Cap Mountain Guides for your quality observations and collaboration that helps to build a more informed avalanche forecast.  

Thank you for your recent observations...you are adding valuable information to our forecasts.  Keep 'em comin'! 

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