Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Give the snowpack time to adjust to the large amount of water we just received. Make conservative terrain choices on Tuesday, staying far away from large avalanche paths and open slopes. Avalanches may be capable of growing very large and running far distances toward roads and trails at lower elevations.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Another day of loading will continue to test the deep layers in our snowpack where a favorable setup for very large avalanches exists. There could be slides on these layers from Monday, but we just don’t know about them yet. If continued snow and wind are able to activate these layers on Tuesday, very large and destructive avalanches will occur. These slabs could release naturally or be triggered by other avalanches stepping down to the Mid-January crust. Continue to give all large avalanche paths and open slopes a wide berth until this storm is over.

    (2/20/2021) This deep avalanche likely failed on the mid-Jan crust Saturday near Stevens Pass. S, 4900' Photo: Wash DOT NCR.

  • Storm Slabs

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

    Continued snow and wind will further develop dangerous Storm Slabs on Tuesday. Slabs will increase in size and reactivity as you ascend in elevation above the previous rain/snow line or where strong winds are able to thicken slabs. Be leery of steep slopes over 35 degrees, leeward slopes near ridgelines, convex rollovers, or rocky areas near cliffs or gullies where triggering an avalanche is more likely. With so much recent snow, any triggered avalanche has the capability of entraining snow, growing large, and traveling far distances. If you see evidence of recent avalanches, cracking in the snow as you travel, textured snow surfaces, or wind-stiffened snow, then avoid all slopes over 35 degrees.  

    (2/21/2021) This natural avalanche occurred on Eagle Peak at Mt. Rainier National Park on Sunday. It started higher up on the mountain before running to the valley bottom, with a large powder cloud that crossed the river and dusted observers. [Photo: Nikki Frumkin]

Avalanche Discussion

There is a lot of uncertainty around conditions in the West South as we transition out of this atmospheric river event. On Tuesday, we don’t believe that you will see a widespread natural avalanche cycle, which has allowed us to drop the hazard level. That doesn’t mean that conditions are safe. You will still be able to trigger avalanches as you travel and very large avalanches could come down from upper elevations into areas many people often consider as safe zones. Although the West South was relatively spared during this event compared to many areas of the region, don’t overlook the recent changes the snowpack has gone through. Over 2.5” of water fell at Paradise since Sunday afternoon, with areas closer to the crest ranging from 1.15-1.75” according to NWAC’s weather stations. That’s a lot of water in a relatively short period of time and we are not done yet.

At lower elevations, a lot of this precipitation fell as rain. The general cooling trend should help to minimize wet avalanche activity on Tuesday, but it can take some time for water to percolate through the snowpack and weaken the bonds between snow crystals, releasing surprising natural avalanches. You can mitigate this risk by minimizing your exposure through the selection of safe travel routes, staying off slopes over 35 degrees, and being aware of terrain above you at all times. Winds were also significant during this event and dry snow was easily transported into sensitive Wind Slabs that were already being triggered by humans on Saturday afternoon. Near ridgelines, cornices may have been freshly built by wind and new snow or destabilized by the rain, ready to act as triggers for the slopes below. Again, choose safe travel routes staying far away from large avalanche paths, open slopes, and avalanche runout zones on Tuesday while the snowpack takes time to heal. 

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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