Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Wednesday night's cold temperatures helped to decrease the likelihood of wet avalanches. However, small wet avalanches may still be a concern in very steep rocky terrain. Although unlikely, you could trigger an avalanche on deeper weak layers in high elevation northerly terrain. Approach new alpine terrain cautiously and consider taking lower angle routes on shady slopes above 6000ft. 

Problemi valanghivi

  • Persistent Slabs

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

    Spring temperature fluctuations and a good freeze overnight on Wednesday are decreasing the likelihood of triggering these large persistent slab avalanches. However, there is still a lot of uncertainty on how the snowpack is adjusting at these upper elevations. The last reported avalanche on this layer was less than a week ago, on March 20th. You can still locate this weak structure in profiles at upper elevations on shady slopes. This layer could be stubborn, and you may not get direct signs of instability such as collapsing or cracking before a slope avalanches. The lack of bullseye observations of instability and the variability of this layer is unsettling because it is difficult to discern which slopes may avalanche. Therefore, it is best to approach all steep northerly aspects at upper elevations with suspicion. 

    Any avalanche that runs on the crust could be a couple of feet deep and fairly wide. Consider traveling on lower angled slopes in northerly terrain above 6000ft. Large loads like cornice failures or snowmobiles could initiate persistent slabs more easily.

    Example recent slab avalanche from the East South zone.

    Photo: Andrew Kiefer

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1–1.5

    The snowpack is likely adjusting to the warm temperatures and trending towards a diurnal spring melt-freeze cycle. On Wednesday, cold overnight temperatures resulted in a solid refreeze of the upper snowpack and decreased the likelihood of wet loose avalanches. However, as the day warms up on Friday, small wet loose avalanches may become a concern in very steep terrain. The daily temperature fluctuations in the springtime are more significant than earlier in the winter. A cold night with a good refreeze of the snow surface can decrease the likelihood of wet avalanches the following day as the temperatures climb back to well above freezing. So, take note of how well the snow surface when you start your day. If you easily punch through a thin crust, wet avalanches will be more likely. If the snow surface is well frozen and supportable wet avalanches are less likely. You should still look for signs of wet loose avalanches such as rollerballs and fresh fan-shaped avalanches, and if you begin to sink deeply into wet, heavy snow as the day warms up, it is best to stick to lower angle slopes. Even though the expected size is relatively small, keep in mind that even small avalanches can have high consequences in extreme terrain.

    Any large cornice falls could be dangerous in their own right, and they could also trigger deeper avalanches below. Attempt to minimize your time underneath lingering under large overhung cornices, and don't be afraid to steer widely around potential runout zones. Some shaded, northerly aspects near and above treeline may still harbor more deeply buried faceted layers. Large triggers, such as cornices, could initiate deeper slab avalanches on these layers.

    (1/24/2022)

    Example of small loose wet slides. Big Slide Creek in upper Icicle Creek drainage.

    Photo: Matt Primomo

Avalanche Discussion

Observers have been documenting weaker, faceted grains or surface hoar overlying a crust from early March on W-N-E aspects from Stemilt Basin to Icicle Creek and other areas to the north and south. Above 5,500ft, these slopes harbor weaker, faceted grains over a crust from early March. This layer could be down 2ft deep or greater in some areas. On Sunday, skiers triggered an avalanche on it near Mt Fernow that was 2ft deep and 40ft wide. Observers in the Chiwaukum range also found the weak layer above 5,000ft and reported significant wind loading on Saturday. Matt Primomo found the March 8th facets in the White Pine drainage on Friday. A vague observation of large collapses in the Cle River Drainage also came in from Saturday. If you are traveling in the mountains, help us track this layer by submitting an observation.

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