Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

A very cold, blustery day is in store for Thursday. Strong easterly winds will build fresh wind slabs near and above treeline. Avoid steep slopes where you witness active wind loading to reduce the chance of triggering an avalanche.

Avalanche problems

  • Wind Slabs

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

    Gusty winds and plenty of light-density snow available for transport equal fresh wind slabs. East winds often come with an unusual pattern. Some mountains and ridges will see sustained strong winds - with lots of wind transport and slab formation - while other areas might stay calm. There will likely be stronger winds farther east in the zone and near the Passes but be ready to see them anywhere.

    Blowing snow will be the main observation to identify areas of active wind loading. Test slopes and hand shears will help gauge slab reactivity and depth. You may see slabs form farther downslope or on different aspects than usual.

    In sheltered terrain older slabs are becoming difficult to trigger but you might still find one on a steep unsupported feature like a convex rollover. 

    Example of the wind scouring snow from windward terrain and transporting it onto leeward slopes below.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    There is no shortage of light-density snow out there. Dry loose avalanches will mostly be small and present little danger. It could be a different case with terrain traps in the runout or in big terrain where they can run far and entrain more snow in the process.

    Clearing skies and sun offset by very cold temperatures won’t be enough to trigger wet loose avalanches. A bit of warming could cause trees and rocks to shed snow which could in turn trigger loose snow avalanches.

    These kinds of avalanches shouldn’t take you by surprise - keep an eye on slopes overhead as the sun comes out and stay alert to the amount of snow moving with you if travelling on steep slopes.

    (2/21/2023)

    Natural dry loose avalanches.

Avalanche Discussion

An NWAC Observer near Darrington found 1' of light density new snow over crust below treeline Wednesday. New snow layering was observed as right side up and danger from slab avalanches was limited to wind loaded terrain. 

Strong westerly flow during the last storm favored the western regions of the zone with over 6” of precipitation and many feet of new snow near and above treeline. Moving inland the White Chuck Tripod picked up about 2’ of new snow with slightly less at Stevens Pass. A similar west versus east pattern was reported from West North.

Natural avalanches to D2 were reported from Snoqualmie Pass and West North on Monday with smaller human triggered wind slab and loose snow avalanches the theme on Tuesday. The outlier avalanche was a  large natural that ran over 3000’ from high on the south side of the ridge connecting Church Mt. and Excelsior Pass (West North) down to 1900’ and put a 10’ debris pile on Church Mt. Road.

Regions covered