Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

After a springlike weekend, the West South zone will return to winter and dangerous avalanche conditions on Monday. Avalanche potential should increase throughout the day as strong winds redistribute accumulating storm snow. If you notice cracking of the snow surface or new avalanches, be sure to avoid slopes over 35 degrees.

Avalanche problems

  • Storm Slabs

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

    The winds are significant with this storm and you will likely start your day managing primarily wind-loaded slopes. Actively blowing snow will be a constant throughout the event, creating thicker and more sensitive slabs on leeward slopes or near rocky features. As the day progresses and storm accumulations increase, the distribution of dangerous slabs is expected to expand to all slopes over 35 degrees. Larger and potentially more reactive slabs will exist as you ascend in elevation or in those wind-loaded areas. Using uptrack tests or small test slopes can help you determine how easily and deeply the new snow is failing. Digging quick hand pits to check the initial bond and locate interstorm layers of concern can further help you identify slab potential. Once 6 inches of new snow has accumulated, your best bet will be to avoid slopes over 35 degrees where triggering an avalanche is more likely.

    (2/9/2023)

    Using uptrack tests can give you an indication of slab potential. Here we see cracking of the snow surface meaning that this slope may be unstable.

    Photo: Susie Glass

Avalanche Discussion

The West South is expected to get a range of snowfall accumulations out of the incoming storm, meaning the depth, reactivity, and to an extent, character, of slabs may vary around the zone. The volcanoes and areas further south should outpace snowfall-wise, with areas closer to the crest likely having gustier winds. 

That said, the general story remains the same. The storm should begin with high-elevation rain on Sunday night before temperatures crash down and allow precipitation to change over to snow by daybreak on Monday. The rain should continue to wipe out any weak surfaces we have around the zone which likely are already in decline due to Sunday’s warm weather.

Our expectation is that the new snow should bond fairly well initially to the wet and warm surface. Throughout the day, there will be periods of high precipitation rates, plenty of wind, and possibly a sagging convergence zone hitting the northern part of the zone. You could see a round of small natural avalanches as the hazard increases throughout the day. 

We believe the upper snowpack above the 2/3 interface to be generally right-side-up and strong. You may still be able to find some older interfaces in this snow that show the ability to fail, but no recent avalanches have been reported on them. We anticipate you will be dealing with primarily new snow problems on Monday but wouldn't be surprised to hear of a deeper release in isolated locations. If you find yourself on a volcano and observe significant accumulations at high snowfall intensities, you could cross the threshold into very dangerous avalanche conditions near day's end.

Regions covered