Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

0730 Update:  Near Treeline increased to Considerable Danger. Overnight snow and wind has increased the avalanche danger. You can trigger slab avalanches in wind affected snow near and above treeline.  Avoid open slopes steeper than 35 degrees with freshly drifted snow.

Problemi valanghivi

  • Wind Slabs

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

    0730 Update:  Near Treeline increased to Considerable Danger.  9" of snow has accumulated in the Stevens Pass area overnight through 0700 this morning with moderate west ridgeline winds.  This has increased the likelihood and potential size of wind slabs on lee slopes near and above treeline.  You may trigger small storm slabs on convex rollovers, or steep unsupported slopes anywhere you find ~6" or more inches of fresh snow including below treeline. Previous discussion below.  

    Depending on how much snow we receive, danger may increase to Considerable in upper elevation terrain on Monday. Snow that fell before Sunday has generally shown signs of good bonding to underlying layers. Around 6 inches is forecasted for Sunday night, and it may form into reactive wind slabs up to a foot or more deep. Triggering an avalanche in these slabs could be large enough to bury or injure you. 

    You can quickly dig through the surface snow as you travel and identify how well it is bonded to the underlying layer. Search for signs of wind loading such as pillows and textured surfaces. Feel for firm or hollow snow. Use small test slopes before exposing yourself to larger features. Avoid wind loaded slopes greater than 35 degrees in higher elevation terrain.

    An example of a skier triggered wind slab on Tye Peak which occurred earlier this year, similar to what you might see on Monday.

Avalanche Discussion

An NWAC forecaster skied up to 6400ft in the Steven’s Pass zone on Sunday, where he found small isolated drifts 20-30cm deep. The drifts were generally unreactive, except he avoided obvious features where they may have been more reactive. He also saw a small dry loose avalanche on a north facing slope. Dry loose avalanches might occur in the new snow on non-wind affected steep slopes on Monday also.  

Maintain awareness of cornices. Give them plenty of room when traveling on ridges and stay out from under them. Several large glide cracks and a few glide avalanches were observed recently as well. If you notice crevasse-like cracks in the snowpack, avoid areas below the cracks. 

While deep persistent slab avalanches are dormant and unlikely, you can still find the snowpack structure in the zone. The mid-January weak layer is now buried 8-9 feet deep and shows signs of strengthening. The last known deep slab avalanche in this zone was on March 1, and one was suspected in the West South zone on March 3. Major warming events later in spring and summer could trigger further rounds of avalanches on this layer. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Regioni coperte