Bollettino valanghe

West Slopes North

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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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Saturday will be the not-so-calm before the storm with 2-6” of new snow and winds strong enough to drift in onto downwind slopes. Keep an eye out for smooth, wind-drifted snow. There is minimal danger out of freshly wind-loaded terrain

Problemi valanghivi

  • Wind Slabs

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

    The real storm is on its way for Sunday, but light snowfall and strong winds ahead of it should start to build shallow slabs on leeward slopes. With westerly winds, places like the Sisters Range and Mt. Baker should see a bit more snow and stronger winds than locations more to the east. 

    Blowing and drifting snow should show you where new slabs are forming. With some sort of crust on nearly all aspects and elevations, it should be easy to track where the new snow might be deep enough to form a slab. You are most likely to see them on leeward slopes just below ridgeline. Look for more widespread slab formation if we see more snow and stronger winds than forecast.

     

    (2/26/2023)

    Use small, wind loaded features to test wind slabs.

    Photo: Jason Speer - Baker Mountain Guides

Avalanche Discussion

No new avalanches were observed around Hwy 542 on Friday despite another day of sun and above-freezing temperatures. Between intermittent clouds and light but cool winds, slopes warmed enough to soften but not break down Thursday’s crust and produce more avalanches. Weather stations in other parts of the forecast zone recorded much warmer temperatures than Heather Meadows and Pan Dome. 

The most noteworthy observations going into the weekend have to do with snowpack structure. While the facets above the Early February Crust (EFC) were found to be quite rounded and resistant to propagation in many areas, in others, they are still well-defined and produce propagation in testing. 

At 5000’ in the Baker BC, there are two or more feet over the EFC, the facets are rounding, and testing shows minimal propagation. At 5500’ in Canyon Creek, the EFC is down only a foot or so, but results are similar. At 5700’ near Yellow Aster Butte, it is also down a bit more than a foot, but the facets are very soft, well-defined, and propagate easily in testing.

Widespread surface hoar observed Friday is also a wild card. The sun beat it down on solar aspects, and it will likely get blown off exposed terrain. But it may get capped and buried on shaded and sheltered slopes. Other layer interfaces in the upper snowpack also continue to show easy results with tilt tests, etc.

The take-home pay is the snowpack varies a ton from slope to slope due to variations in snowpack structure, wind scouring and loading, and sun exposure. We may see a wide range of avalanche activity - with no discernable pattern - with heavy snowfall and wind loading in the forecast.

 

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