Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Mid and upper elevatation terrain could hold fresh wind slabs Saturday. Be on the lookout for and bypass steep terrain with recently wind drifted snow. Lower elevations should be generally safe.  Continue to practice good travel habits and reassess your plan if you find conditions different than expected.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Saturday should be a bit of a repeat with moderate westerly winds and another 3-6” of new snow in the forecast. Wind slabs will be easier to trigger where they initially formed over crust or weak, faceted snow and surface hoar. Hand shear and shovel tilt tests can highlight a weak interface below the latest storm and wind slabs.

    Scoured or eroded surfaces used to help determine the pattern of loading could be hidden by light new snow that fell with less wind. Track the depth and stiffness of new snow layers as you gain elevation and switch aspects to help identify areas of wind slab. Look for and test freshly wind drifted features to get a feel for the reactivity of fresh wind slabs. When in doubt just steer around steep wind loaded features on lower angle and well supported terrain. 

    Rime and scoured surfaces helped us anticipate wind loaded slopes. 

Avalanche Discussion

Dry loose snow avalanches are probably the most common sign of instability you will see Saturday. Sluffs shouldn't grow too large - but keep an eye on how much snow is moving around or behind you if venturing into steeper terrain.

Snow amounts from the latest weather system trended towards higher in the north with less new snow traveling farther south in the Cascades. Heather Meadows picked up  6-8" of snow overnight with other West North weather stations seeing up to 1.0" of SWE equaling about 10" of new snow. West Central weather stations recorded  anywhere from 0.1-0.7" of SWE. Stevens and Snoqualmie Pass saw a trace to a few inches of new snow (obs).

Field observations were limited on the West Slopes. Reported activity consisted of dry loose snow avalanches in terrain steeper than 40 degrees. A small human triggered wind slab was reported from West North on Thursday (obs).

A pattern of isolated but large natural and human triggered avalanches has played out in the past week in the zones surrounding West Central. Though details vary in terms of layering, triggering and terrain, all of the reported avalanches show that the current snowpack is not entirely bombproof.  Though large avalanches in deeper layers are becoming unlikely, a big load from heavy snowfall, rain, falling cornice, or a smaller avalanche could still wake one up. Check the forecasts for neighboring zones for more information.

 

 

 

 

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