Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

Freezing levels of 5000  feet and rising, a storm bringing several inches of snow at upper elevations and rain down low sets the alarm bells off for very dangerous avalanche conditions. A lot of uncertainty exists with how the snowpack will handle this new precipitation, but there is a good chance you will find thick, reactive slabs of snow at upper elevations, and wet snow that slides easily at lower areas. Avoid all avalanche terrain as this storm runs its course, including lowland or flatter areas with large swaths of steep snow-coated terrain above you. 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    Upper elevations could see six inches of snow by morning,  and another foot+ during the day.  Expect heavy, wind-affected snow, with subtle slabs that you are very likely to trigger. Most avalanches will probably remain in the new snow layer, a foot or less deep, but there is a small possibility that avalanches could break deeper, taking more of the snow we received in the last week.

    Avalanches could occur in all areas where 6 or more inches of snow accumulates, but they are even more likely in areas where wind deposits snow into thicker, heavier drifts. Your best chance at avoiding avalanches during this storm is to stick to low-angle slopes, away from steep overhead terrain. Find slopes less than 30 degrees, and avoid flat terrain beneath large, steep slopes. 

    (1/4/2022)

    In this photo, small avalanches were easily triggered in the new snow. This is similar to how you may find conditions on Tuesday. 

    Photo: Zack Mcgill

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Rain will absorb into the snowpack at elevations below approximately 5000ft. Wet loose avalanches are most reactive when a dry snowpack encounters rain or warm temperatures for the first time. The sun moistened southerly aspects on Sunday, and many of those areas saw small rollerballs running down steep slopes, breaking up the smooth surfaces and forming a subsequent thin crust. Northerly aspects have not been as affected yet, so you may find those areas more reactive as they receive rain.

      Wet snow makes for challenging travel, especially if enough water absorbs so that you're sinking several feet down into the snow. In areas where these conditions are present, or any wet, sticky surfaces, stay alert for the possibility of wet loose avalanches. If you see rollerballs running down steep slopes, or find signs of recent wet loose avalanches, stay off steep slopes and the areas beneath them. 

    (12/31/2021)

    Wet loose avalanche were easily triggered in recent warm conditions.  The slide packed a punch for it's smaller size (D1.5) You may encounter similar conditions on Tuesday. 

    Photo: Matt Primomo

Avalanche Discussion

Very large avalanches were reported in neighboring zones in the last several days, including one at Snoqualmie Pass, discovered Saturday. Not much information is known about these avalanches, although it is believed they failed in layers buried several feet deep, rather than in newer storm layers. There is a possibility these deep weaknesses could exist in the West Central Zone as well. As temperatures increase and more weight is added to the snowpack, keep the small chances of this type of very large avalanche occurring in the back of your mind. Consider that large deep slab avalanches from higher terrain could run into lower elevations where otherwise you might not expect to encounter a large avalanche. 

A lot of uncertainty exists as to how many avalanches we will see in this storm. The heavy nature of the snow could mean that it remains stubborn, staying in place. Lower elevations may have already been affected enough by warm temperatures in the last few days, resulting in absorbing rain without producing avalanches. Conversely, the snowpack could be reactive, producing several large avalanches. Expect danger to increase as more precipitation falls during the day as well. Due to all the unknowns, treat the snowpack with suspicion and travel carefully if you're in the backcountry Tuesday. 

Regioni coperte