Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Strong winds, snow, and fluctuating freezing levels will be enough to reach dangerous avalanche conditions by sunset in the West South. Make sure you have travel plans that allow you to escape to lower-angled terrain once this storm arrives in the afternoon.

Avalanche problems

  • Wind Slabs

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

    Increasing winds throughout the day will transport newly fallen snow into Wind Slabs. These slabs are often formed on leeward slopes near ridgelines, the side of gullies, or the base of cliffs. Apart from these locations, steep slopes over 35 degrees and convex rollovers may be the most likely spots for you to trigger a slab on Sunday. With such strong winds, actively blowing snow should be your first indicator of Wind Slab development and their location. You can also look for freshly building cornices or if you have visibility, textured snow surfaces to help you identify potential areas of danger. Use test slopes, hand pits, and uptrack tests in non-consequential terrain to help you identify how the new snow has bonded to the previous surfaces and if a slab exists. If you notice a poor bond or cracking in the new snow as you travel, avoid slopes over 35 degrees, particularly ones you suspect are wind-loaded.

    (3/26/2021) Look for shallow wind slabs such as these found at White Pass on Friday (3/26) to develop and thicken throughout the day as more snow and wind accumulates. [NE 6200']

Avalanche Discussion

Sunday’s storm is forecasted to pack a bit more of a punch than what we may be used to in the springtime. The predicted wind speeds of 40-55 mph by day’s end really jump out to us, and the rate at which it approaches the region is uncharacteristic. Although it approaches quickly, we shouldn’t see stormy weather really start to impact the zone until the afternoon hours. So you may not see the avalanche hazard we are predicting if you decide to make an early morning trip to the mountains. However, if the forecast holds, heavy snow and plenty of wind should result in dangerous avalanche conditions by day’s end. The hazard will be greater as you ascend in elevation, but don’t be surprised to see the wind blowing snow around at lower elevations as well. The bulk of the precipitation is forecasted to hit the Paradise area, but there should be enough snow and wind in other parts of the zone that dangerous avalanche conditions are reached. In the morning hours and at the onset of precipitation, warmer temperatures could help drive some Wet Loose avalanches at lower elevations, possibly triggered by rain. These avalanches could be more likely on slopes that have not seen direct sunshine lately and are still harboring colder, drier snow, particularly as you reach middle elevations. If rain is starting to fall, take note of your location in terrain and head toward lower angled slopes, keeping away from any overhead hazard.

Around the zone, most surfaces were wet and moist from the sunshine the past few days, which could result in a favorable bond with the new snow. However, some slopes may have “firmed up”, creating a crust to act as a bedsurface for the newly fallen snow. This could result in avalanches running far and fast, either as slabs or as loose avalanches in steep terrain. Be sure to evaluate the bonding of new snow carefully, it could vary greatly depending on what prior snow surface is present. Apart from the potential slabs, cornice development will be aided by the strong winds associated with this storm. Look for current cornices to thicken and fresh cornices to develop on leeward ridgelines. These beasts are always susceptible to human triggers, so give cornices a wide berth by not traveling on them and minimizing time spent below them.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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