Bulletin d’avalanche

Blues

Wallowa Avalanche Center
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Danger d’avalanche

Fri
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

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.  Lower elevations that receive rain instead of snow could produce wet snow avalanches.   If you head into the backcountry, choose wind-sheltered terrain less than 30 degrees.  

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

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2.5

    6" of wet, heavy snow fell overnight combined with moderate to strong winds out of the South.  The Snow Water Equivalent of last night's snow was 1".   Expect another 2-4" of snow today with continued strong wind gusts out of the South.  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.  

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–1.5

    If you find yourself below the snow line where it is raining, expect the snowpack to lose cohesion and wet loose avalanches to be likely.  Look for signs of instability such as roller balls or pinwheels.  If you step off your machine or skis and sink up to your boot tops in wet sloppy snow, it's time to boogie out of the mountains.   While these avalanches may remain quite small, they can be difficult to escape and could easily push you into a terrain trap such as a gully, creek, or over a cliff band where the consequences of being caught would be amplified.  

    Pinwheels are often the precursor to wet loose avalanches.  A telltale clue.  

    Photo: Karen Morse

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?  The snowpack in the Blues is made up of mostly dense snow and crusts.  We received a public observation yesterday from an East aspect at 5200' near Tollgate.  The height of snow there was just over 3 feet.   Check out WAC forecaster Tom Whipple's observation from the Blues from a week ago here.  Observations are sparse, so please submit your observations to us if you travel in the backcountry of the Blue Mountains.  

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