Avalanche forecast

West Slopes South

Northwest Avalanche Center
View on map

Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Another round of wind and snow will help to create dangerous avalanche conditions on Sunday. The storm may be more pronounced on the volcanoes or southern part of the zone, but there will be unstable pockets of wind-drifted snow regardless of your location. If you see fresh cornices, actively blowing snow, or shooting cracks, dial back your terrain choices to avoid wind-loaded slopes over 35 degrees.

Avalanche problems

  • Wind Slabs

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

    Winds should remain strong enough to blow around freshly fallen snow into unstable Wind Slabs on Sunday throughout the West South. Look for these slabs to develop on the leeward side of ridgelines, on convex features, or near rocky terrain such as confined chutes or the base of cliffs. Slabs should be thicker and possibly more reactive as you ascend in elevation, but could develop even down in the trees. You can use visual clues such as textured surfaces, freshly built cornices, or actively blowing snow to help you find where Wind Slabs may have developed. Using small test slopes or upslopes tests are great ways to determine how the snow is reacting to your weight and if a slab is present. If you notice cracking of the surface or that the snow is firm and feels hollow, you should head for slopes under 35 degrees that are sheltered from the wind.

    (4/9/2022)

    A small (D1) Wind Slab triggered by a skier near a ridgeline in the White Pass backcountry. Note the cornice as a visual clue that the slope below may have been wind-loaded. [E 6150']

    Photo: Dallas Glass

Avalanche Discussion

Despite what the calendar says, we’re in the midst of a storm parade that is delivering winter-like weather to the West South. The first round of precipitation brought anywhere from 6-8” of low-density snow to the zone, accompanied by strong winds. This snow is sitting atop the 4/8 melt-freeze crust and reportedly has bonded fairly well. That said, the wind was able to drift new snow into larger drifts in many locations, and on Saturday, avalanche professionals near White Pass were able to trigger Wind Slabs up to 1 foot deep on test slopes and convex features. 

Another wave of snow and wind is targeting the West South on Sunday. If you are recreating in the southern part of the zone or on a volcano, you may feel the brunt of this storm more than areas further north. Regardless of your location, the storm should have its greatest impact in the morning hours before transitioning into a more showery pattern. The depth of snow over the 4/8 crust will incrementally increase and the winds should again be strong enough to drift the low-density storm snow into thicker slabs. While Wind Slabs may be the most concerning problem you will need to manage, loose avalanche problems (both dry and wet) should have your attention as well. Low-density dry snow could run far and fast on steeper slopes. Additionally, it doesn’t take much sun this time of year to start to weaken cold dry snow and produce natural avalanches. If there are periods of sunshine throughout the day on Sunday, look for fresh rollerballs or snow shedding from trees and rocks as signs that small loose avalanches may follow. While we expect the majority of these avalanches to be small, don’t get swept off your feet in consequential terrain.

Regions covered