Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Sunshine and rising temperatures will weaken the surface snow and increase the likelihood that you can trigger a wet loose avalanche on sun-exposed slopes steeper than 35 degrees. Use caution on slopes receiving direct sunshine where you find wet snow surfaces. The possibility of wind slabs lingering at higher elevations near cornices and on midslope features still exists after a windy couple of days. Look for wind-stiffened or textured surfaces and steer around features over 35 degrees where you see wind accumulated snow.

Avalanche problems

  • Loose Wet

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

    10-14 inches of fresh snow was deposited Sunday and Monday which will react quickly to Tuesday's sunshine. It is possible that convective clouds may form at some point in the day which may slow the formation of wet loose avalanches.  However, the days are long and sunshine is likely.  When the sun breaks out in your part of the mountains,  the potential for wet loose avalanches will quickly rise on steep sunny slopes.  Wet loose avalanches may release naturally below steep rock faces that catch the sun.  If you see pinwheels or rollerballs or find yourself sinking into wet surface snow more than ankle-deep,  choose lower angle or shadier terrain. Trees beginning to shed snow or drip water are a clear sign that wet loose avalanches can be triggered.

    (3/25/2021) Wet Loose activity, such as rollerballs and small avalanches, were observed at Mount St. Helens on Thursday. This type of activity is often the first sign that larger wet loose avalanches may occur. [Photo: John Darmody]

  • Wind Slabs

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

    Throughout the zone, strong to extreme winds have transported new snow into wind slabs. Incredibly strong winds likely scoured and compacted the snow at upper elevations. The likelihood for wind slabs is highest at middle elevations and these slabs may linger in unusual locations and further downslope than typical due to the strong winds. Fresh cornices will be sensitive to human triggers but can be used as a visual clue to help you identify wind-loaded slopes. Other clues such as textured surfaces or smooth pillow-like piles of snow can help you identify wind-loaded slopes to avoid. Wind slab avalanches will be most likely on slopes over 35 degrees, near rocks, or on convexities. Use small and non-consequential wind-loaded terrain features for uptrack tests or hand pits to help you determine slab potential and some clues to bonding. If you find a poor bond or suspect wind-loading avoid slopes and features over 35 degrees.

    (11/27/2020) Active wind loading/blowing snow, rime on trees and cliffs, and snowdrifts are all indicators for Wind Slabs

Avalanche Discussion

NWAC’s weather stations were spinning all day on Sunday, cranking out huge wind numbers around the zone. Camp Muir takes the cake with 15 hours straight of gusts over 100 mph. During their windiest hour (4:00 pm), we recorded a maximum gust of 143mph, with an average speed of 119mph and a minimum of 98 mph. Those numbers are ridiculous! Although they are the top end of numbers recorded around the zone, they illustrate that this is a windy storm. NWAC stations closer to the crest support this notion, with gusts that approached 100mph and multiple hours with wind speed averages in the 40s and 50s. This storm was definitely more winterlike than springlike, but Tuesday's mostly clear weather will change that.

Observations by NWAC forecasters on Sunday indicate that the new snow is not bonding well to the prior snow surface, particularly in areas where a melt-freeze crust existed. This crust varied in thickness but existed in all elevation bands and on most aspects except northerly at upper elevations. This poor bond was due in part to graupel falling near the onset of precipitation. Avalanches will have the potential to run far and fast on the crust as slabs or wet loose. 

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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