Bulletin d’avalanche

Blues

Wallowa Avalanche Center
Voir sur la carte

Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Timing and aspect selection are the two best strategies for you today as we will see the warmest temperatures of the week.  Wet Loose Avalanches will be likely in the afternoon and may first be triggered on east aspects, then south aspects followed by west aspects.  Look for signs of warming such as pinwheels and point releases out of rock bands to guide your timing.  There is also the possibility of triggering a lingering windslab along leeward ridgelines.  As we see warmer days with longer sun exposure, cornices will also likely become weaker and be prone to failure.  

Problèmes avalancheux

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Wet Loose avalanches will be likely to be triggered today as we have the warmest temperatures of the week coupled with fairly calm conditions.  We have not yet entered a real corn cycle or melt freeze cycle, and our upper snowpack is still in a transitional phase.   When dealing with wet snow, keep an eye on the overnight temperatures for the nearest weather station where you are heading.  Freezing overnight temperatures and convective cooling through wind will help delay the wet snow avalanche problems.  Monitor the thickness of the melt freeze crust on different aspects throughout the day and note how quickly it is softening.    If you find your track easily trenching into wet snow, or your boots are sinking into wet snow, it is time to choose a shadier aspect.   Carefully plan an appropriate exit route from the mountains that does not put you underneath consequential terrain which is getting baked by the sun and warm temperatures.  

    (3/12/2021) A clear sign things are warming up!

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Look for smooth or rippled pillow like features along ridgelines.  I found windslabs to be mostly small, but still reactive on North aspects yesterday.   Look for wind loading patterns in your zone today.  Utilize small, safe, representative test slopes near ridgelines to test the reactiveness of any suspect areas.  If commiting to a slope that is windloaded, avoid entering it through the wind loaded snow.  

    (3/12/2021) up to 6" deep isolated to ridgetop.

Avalanche Discussion

It's kinda like a dollar store out there.  There's a little bit of everything and the shelves are full!  Things are filling in very nicely.  On an observation tour in the Western Wallowas, I found an average total height of snow around 240 cm (almost 8 feet) across a variety of aspects at 7800'.  The 2/22 Rain Crust was found between 60-80 cm (2-2.5') from the surface.   

I could see evidence of old dry loose avalanches as well as some filled in wind slab avalanches along North and East aspects.  Not surprising, as reports of natural avalanches trickled in from the Northern to Southern Wallowas this last week following the storm during the early part of the work week- All of these sound like they were on North and East aspects near wind loaded ridgelines.   

Solar (South and West) aspects showed signs of warming with rollerballs and pinwheels releasing naturally out of rock bands from Thursday.  South and West aspects also held a breakable melt freeze crust that was about 1/2" thick which capped dry snow just below.   

East and North aspects- where not wind affected- held cold snow that rode well.   These aspects are holding the best snow, but it is also the weakest snow surface out there.   The surface snow is weaking through faceting.  In steeper (>35 degrees) North facing terrain, dry loose avalanches will still be possible to trigger.  As you travel around the mountains before the next storm, make note of where this weaker snow may be.  In areas near treeline that are sheltered from the wind and sun, observers have noted surface hoar (hoar frost).  During these dry spells, it is also be possible for melt freeze crusts to develop hoar frost on them (smooth bed surface below a  weak layer)...a perfect recipe for avalanches once a new load is added. 

Cornices are in prime failure conditions.  With the increase in temperature and direct sun, these will become weaker and more prone to failure.  Give cornices a wide berth, and expect them to break further back along ridgelines than you might think.  

Régions couvertes