Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Expect shallow, but reactive wind slabs on steep or unsupported slopes at upper elevations. The chances for deep persistent slabs have decreased, but the consequences remain high if one does release. Small loose wet avalanches may occur on steep slopes that face the sun if you find more than 5" of new snow.

Problemi valanghivi

  • Wind Slabs

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

    Blowing snow could be observed at ridgelines from afar on Sunday, and observers found reactive wind slabs in adjacent zones. These slabs could be just a little larger on Monday with another inch or two of snow, and more wind.  Steer around obvious wind features like freshly drifted snow and wind pillows.  Shooting cracks or hollow-sounding snow are signs you could trigger an avalanche on similar slopes. Avoid steep slopes below cliff bands where spin drifts may form wind slabs. A wind slab avalanche could be enough to trigger a much larger deep slab avalanche in some terrain. 

    Cornices are large and sagging in some areas, keep on the lookout for these and avoid spending time under them. Stronger sun and fresh snow could make for small wet loose avalanches where more than 5" of snow sits over a crust. Keep these on your radar as the daytime begins to warm up. Look for roller balls and wet, sticky snow as a sign that these could begin happening on steep slopes near you.

    Example wind slab in alpine terrain.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    It's been about a week since the last known deep slab avalanche but the snowpack structure to create them remains in place.  Be intentional about where and how you travel, and be sure to discuss this with your partners.  If you flip through some of the photos in the media reel below, you'll see some of these monster avalanches have coursed thousands of feet, broken mature trees, and pushed through areas you might not normally think twice about stopping. 

    The way to stay safe is simple: Avoid traveling in or lingering under large avalanche paths. Use extra caution on any steep slope, even around sparse trees. Before you commit to traveling in avalanche terrain, ask  "What's the largest avalanche that this slope can produce, are we willing to take that risk, and are there a safer options?"

    (3/1/2021) A very large avalanche (D3) was triggered by WSDOT highway forecasters on March 1st in a portion of the West Camp path on Rock Mtn. Adjacent sections of this avalanche path ran naturally on Feb 26th. Photo: WSDOT

Avalanche Discussion

Over the weekend, a cool, snow showery regime set up. Now we have at least a few inches of new snow over old snow surfaces. Observers found 4-8" of new snow at Blewett Pass on Saturday, and reactive wind slabs above 5,000ft. The last major storm cycle occurred February 25-26th with ~2" of water equivalent at the Cascade Crest and extreme winds. This came on the heels of an even bigger storm.  From Feb 20-23rd, a massive storm brought up to 6" of water equivalent to the mountains near the crest but much less to the Wenatchee Range further east. Numerous deep and very wide avalanches (Many D3-3.5's, some size D4's)  ran on, or around the 22nd in the mountains near the crest, and some deeper slabs were reported from the Wenatchee Range. Similar-sized avalanches continued earlier this week.

An observer on Wednesday reported widespread very large avalanches in the Chiwaukum range and the Icicle drainage from the most recent cycle. While conditions may be less dangerous in parts of the Wenatchee Mountains, due to less recent snow, the same weak layers can be found and recent avalanches have been triggered on them. In the northern end of the zone, near Holden, the mid-January weak layer is present, though it has produced inconsistent test results. An observer there reported that most avalanches from late February appeared to run on storm interfaces in the upper snowpack.

Regioni coperte