Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

A mix of old and new slabs of wind drifted snow are on the menu for Saturday.  Identify and avoid steep slopes holding wind drifted snow below ridgelines, on convex rolls and unsupported terrain above and around cliffs. Look for wind slabs where you don’t normally see them as well as the usual locations.

Problemi valanghivi

  • Wind Slabs

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

    Southerly winds will build Saturday afternoon and produce another round of wind slabs. In some areas, they will form over a weak snow surface that will make them easier to trigger. Older slabs from easterly winds are mostly unreactive but you could still trigger one at upper elevations.

    Blowing and drifting snow will point the way toward slopes that are actively loading and building plump, smooth-looking slabs. Scoured ridgelines and other wind affected features can also reveal wind slab hideouts. You should probably just avoid these slopes, especially after they have had a few hours to load up and build a legitimate slab. One to three-day-old slabs could still be triggered from steep, unsupported features and around cliffs and rock outcroppings. 

    (2/23/2023)

    A skier was caught and carried in this small wind slab on Thursday in Snoqualmie Pass.  The crown is visible in the narrow chute above tracks and debris. It was triggered while ascending. SW aspect at 5300'.

    Photo: NWAC Public Obs

Avalanche Discussion

Wind slab reactivity varied in the zones around West Central on Friday. A person was caught, carried and injured in a wind slab avalanche above Snow Lake in Snoqualmie Pass. No other avalanches were reported from that area. Observers in Stevens Pass found east winds continuing to transport snow at all elevations. In West North, a few very small slab avalanches were reported from wind loaded, west and south-facing terrain. Loose snow avalanches just didn’t pack the punch observed earlier in the week. Cold temperatures seemed to win out over full sun and few signs of wet avalanche instability were reported in any of the surrounding zones. No observations were submitted from West Central on Friday. 

Weak facets and surface hoar were found on shaded aspects up and down the west slopes and might survive long enough to get buried by the next round of wind and storm slabs. Solar aspects warmed enough that some variation on sun crust should be found in the morning. 

Saturday will be a transition from high pressure to the next storm heading our way. It’s usually easy to anticipate lingering avalanche danger on transition days. The old storm and wind slabs are dated and unreactive. Clouds and wind lower the chance of seeing wet loose avalanches. Finally, there just isn’t enough new snow to significantly increase the danger. 

On the other hand, there is still plenty of loose, light-density snow just waiting to join forces with strong winds that precede a storm. The two variables to keep an eye on are wind speeds and the timing of incoming precipitation. Avalanche danger could rachet up faster than expected if wind or snowfall comes ahead of schedule and/or is more than anticipated.

 

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