Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

The greatest hazard from this storm exists in upper-elevation terrain where the wind can drift dry snow into firmer and deeper slabs. Blowing snow and drifts should point toward the wind-loaded pockets you want to avoid. In some places, these slabs could be more than a foot thick and fail easily on an underlying crust.

Avalanche problems

  • Wind Slabs

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

    This storm will add a few inches of snow to the totals from the week. That could mean 8-12 inches of dry snow to blow around in the wind on Monday. Look for newly forming wind slabs as you travel. If you start to see signs of wind-loading at middle elevations, expect slabs to be bigger and more widespread higher up the mountain. 

    Steer around pillow-like slabs on the lee sides of ridges, near the base of cliffs, and in the tops of chutes. These slabs may react differently depending on what’s underneath. That old surface may change by aspect and elevation to include firm crusts and wet punchy snow.

    Example: (3/21/2023) Clear signs of wind loaded slopes can help you anticipate slabs. Photo: Dallas Glass

Avalanche Discussion

This isn’t a very big storm, but it comes on the heels of several days of mild, snowy weather with periods of sunshine. You may not see that much snow at the weather stations, but higher in the terrain, it’s slowly piled up. IIt’s also springtime and conditions this time of year are more dynamic than mid-winter. Daytime heating, a few breaks in the clouds, or even rain to higher elevations than anticipated can all cause conditions to change rapidly

With this storm, we’re focussing on the wind slab concern, but near the rain-snow line, you may trigger very small wet loose slides. These will be most likely where a few inches of new heavy wet snow sits over a crust or older weak wet grains. These slides should be relatively harmless unless you’re in high-consequence terrain. 

Below the surface, the snowpack is very aspect and elevation dependent. On southerly slopes and at lower elevations, the snowpack is largely made up of wet gains. Some locations seem to be more frozen than others. On shaded aspects at middle and upper elevations, the snow is much drier and stronger. You can still see the persistent weak layers we’ve been talking about for more than a month. Facets on and just above the Early February Crust didn’t magically go away. However, the recent warm weather both tested the snowpack and helped it heal. If you were to encounter a deep persistent slab, it would most likely be in large complex terrain and need a big trigger (cornice fall, ice fall, or other avalanche). 

On Sunday, clouds lingered in the West South zone longer than anticipated. Even still, sun breaks and warm temperatures resulted in several reported wet loose avalanches. These slides occurred even on more shaded E and NE aspects. Between the clouds, breeze, and slightly cooler temperatures, there were fewer avalanches reported than in other nearby zones. 

The recent hot weather took a toll on the lower elevation snowpack. Tree debris, bare ground, and open creek make it feel more like early summer than March.

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