Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Pericolo valanghe

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

Saturday will be a mostly mundane day with light precipitation, cloudy skies, and mild temperatures. The exception will be blustery ridgelines at upper elevations, where you could trigger small avalanches in pockets of wind-drifted snow. Steer around deep drifts in steep alpine terrain. A greater risk may be travel through breakable, freezing-rain crusts at lower elevations. 

Problemi valanghivi

  • Wind Slabs

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

    If you venture to upper elevations, watch for triggering avalanches in recently drifted snow. Actively blowing snow or cornice formations help you identify suspect leeward slopes. Steer around these freshly drifted pillows that get deposited on steep slopes. You can use small test features to see whether the snow cracks or triggers a mini-avalanche.  Hand pits are another great way to quickly assess the bond to the old snow surface across many different slopes as you travel. If the surface snow slides easily, it is more unstable. Cracking or easy shears in hand pits should point you toward lower-angle terrain as a safer option. 

    Wind slabs can be easily triggered if they form over existing weak snow surfaces or slick crusts. Where snow falls on moist surfaces from Friday's warm temperatures and rain, wind slabs may be more difficult to trigger. To account for this variability, analyze each slope individually.

    (3/20/2022)

    This steep, rocky, lee slope below the ridge will be the most likely spot to find a wind slab on Saturday. 

    Photo: Ryan Minton

Avalanche Discussion

Friday brought an icy coating of freezing rain to lower and middle elevations at the summit of Stevens Pass and further east. This helped keep wet-loose avalanches isolated on Friday. With cooler temperatures and less precipitation on Saturday, we don't expect to see any increase in wet avalanche activity. But there may be chunks of snow that slide off steep rocky terrain, so pay attention to what's above you. If surface crusts break down and you start to see rollerballs, consider moving to lower-angle terrain. 

Weak snow surfaces abound, even on southerly aspects where thin crusts formed this week. Upper elevations likely saw snow as the primary precipitation type on Friday, so these layers may be preserved despite Friday's warmup. The cold air east of Stevens Pass finally mixed out on Friday, and lower elevations climbed above freezing. Making lower-elevation surfaces a mixed bag of melt-freeze or freezing-rain crusts. 

In the upper snowpack, the December 24th crust is absent above about 5,400 feet but is roughly 12 inches below the surface at lower elevations. You can find the stout December 18th crust matrix in the middle of the snowpack, 2-3 feet below the surface on most slopes. It may not exist above 6,000ft, though we don't have great data at those elevations. These crusts are good layer markers, but they aren't problematic for avalanches.

Regioni coperte