Lawinenlagebericht

Northern Wallowas

Wallowa Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
4 · Gross
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Kernpunkte

Rapid snowfall rates combined with strong winds will create dangerous avalanche conditions today. If you enter steep slopes loaded with wind-stiffened snow, you can likely trigger a large and potentially deadly avalanche.   If you head into the backcountry, choose wind-sheltered terrain less than 30 degrees.  

Today's forecast is sponsored by: M. Crow Company

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2.5

    2-4" of snow fell in the Northern Wallowas overnight.   The Snow Water Equivalent of last night's snow was .3".   Reported winds from Mt. Howard gusted up to 47 mph last night out of the East, North, and Southeast.   Expect another 6-8" of snow today with continued strong wind gusts out of the South and West.   Wind slabs will be likely to be triggered in exposed terrain, especially along leeward ridgelines.   Look for clues of wind loading such as stiffened dune-like formations that may be downslope from cornices.  You will know you are traveling over a windslab when your machine or boards do not penetrate as deeply into the snow surface.     Avoid exposed and wind-loaded terrain.  

    Example of wind-loaded terrain.  

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    In wind-sheltered areas at lower elevations, you may be able to find reactive slabs of new snow that are not affected by the wind.  This will depend mostly on snow totals in these areas, so throughout your travels, utilize quick hand pits to determine the depth of the new snow and how well it is bonding to the older snow surface.  If the new snow is shearing off cleanly in a cohesive block, you can expect to find reactive storm slabs on terrain steeper than 30 degrees.   Avoid terrain steeper than 30 degrees if seeing these conditions.  Even a small storm slab that is triggered above a terrain trap such as a gully, creek, or cliff could have serious consequences.  

    Example of a storm slab on a test slope. 

Avalanche Discussion

What is it? Our headline story for this holiday week is significant snowfall accompanied by strong winds out of the South/Southwest.  Most avalanches occur during and just after times of intense loading events.  We get the double whammy of loading with this series of storms:  Loading through rapid snowfall rates in combination with wind loading of snow onto leeward slopes.  

Where is it? You will be able to find unstable snow in many locations today.  Today is not the day to toe the line.   If you do decide to travel near or in avalanche terrain, wide terrain margins will be essential.  You can most likely trigger a large avalanche on wind-loaded slopes steeper than 30 degrees.  You will most likely encounter wind-loaded slopes at mid and upper elevations, on most all aspects.    In wind-sheltered areas- if you find new storm snow in the 6-8" depth range, you could potentially trigger a storm slab avalanche.  Additionally, if you find yourself below the snow line- look for signs of wet loose avalanches.  

What to do about it?  Well, it will likely be a pretty nasty day to be out in the mountains with the ongoing intense storm.  It might just be a good day to start brainstorming about some New Year's resolutions, start that new book that your friend gave you, or watch a classic holiday flick.    If you do head out into the hills, I would suggest having a conservative mindset, avoid potential avalanche paths that may be above or adjacent to your intended route, and testing the reactivity of new snow by utilizing small and inconsequential test slopes.  If you see a cohesive slab of snow break at your machine or boards, you can bet that triggering an avalanche on a larger slope is likely.  

What's going on a bit deeper?  We have a mostly right-side-up snowpack below the new snow.  We have been tracking a weak layer that was formed during high pressure around Thanksgiving.  The Thanksgiving Drought Layer (TDL) is a layer of rounding facets (healing sugar snow) that can be found 2-4 feet from the surface.  We have been conducting numerous stability tests to assess the reactiveness of the TDL, and we have not been seeing as reactive results as we were a week ago.  This is a nice trend to see, but I am still weary of this layer.   Suspect areas that may harbor this unstable layer are mid and upper elevations, on the northern half of the compass, and in thin snowpack depths.   You can read some recent observations that target this layer here. 

If you get out into the backcountry today, let us know what you are seeing by submitting an observation here.  

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