Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

You can still trigger a slab of wind drifted snow at upper elevations. You are most likely to trigger one on steep, convex terrain features or above and around cliffs.  Be extra mindful of steep, wind loaded slopes with rocks, cliffs, gullies, or other hazards in the runout.

Problemi valanghivi

  • Wind Slabs

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

    The last bastion of avalanche danger is upper elevation terrain holding wind slabs. They formed with strong easterly winds Tuesday. While some subzones like Schriebers/Baker NRA and alpine terrain in North Cascades NP got hammered, other areas saw way less wind and have lower danger. 

    Wind slabs are getting difficult to trigger and will be even more so Thursday. On the other hand, some slabs are pretty deep to the point even a small avalanche could be damaging if you manage to find one. 

    Stiff wind slabs are difficult to assess with the usual tools like hand pits, etc. They also tend to release suddenly. Look for areas where the snow surface is smoother and surrounded by wind-hammered snow - they should be pretty easy to spot. Best policy might just be to avoid the few places you might trigger one.

     

    (3/29/2023)

    Natural slab avalanche that released with heavy wind loading on Tuesday. Wind loaded terrain was easy to identify after the wind event. If a slope had a south or west aspect, was not crusty or tracked, and had a relatively smooth surface it held wind slab. 

Avalanche Discussion

It appears wet loose avalanches have played themselves out for the time being. Thursday will bring slightly cooler temperatures, increasing clouds, and some wind ahead of a storm this weekend. There is still an outside chance you could see wet avalanche activity or even a glide avalanche anywhere the day starts warm and sunny. Pay attention to slopes overhead.

The flow of observations on the west slopes has slowed to a trickle with the arrival of spring - but there are always weather stations. Stevens and Snoqualmie Pass saw nearly two days of steady and strong easterly winds that likely redistributed any loose snow available for transport. The White Chuck Tripod, a sheltered weather station set up primarily for snow depth, showed measurable wind back through Monday. The Central Cascades probably saw their fair share of wind Tuesday.

An NWAC Forecaster on the south side of Baker found a number of small but deep wind slab avalanches on west aspects above treeline. They occurred naturally with strong winds and rapid loading Tuesday and released above a sun crust that formed over the weekend and Monday. They didn’t show much reactivity in testing but one slab sticking to a very steep  breakover produced a whumph when approached from the side.

Triggering an avalanche in a layer of weak facets and surface hoar buried in the last storm is unlikely. But unlikely isn’t impossible so don’t ignore obvious signs of instability like whumphing or shooting cracks if you find one of the rare places the setup still exists. Sheltered, northerly terrain is where this layer might still be hanging on under snow from the last storm.

 

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