Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

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

Large and very dangerous avalanches will occur on Tuesday as this storm winds down. On Monday multiple large natural avalanches ran off Mt Herman, nearly hitting a group of ski tourers in the valley below. Stay out of all avalanche terrain including low angle areas below steep slopes for one more day while the snowpack adjusts to all the new snow. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    You can trigger touchy wind slabs avalanches up to several feet thick at mid to upper elevations on Tuesday. Numerous natural and human triggered avalanches occurred in the last few days as precipitation steadily continued.  In a close call on Monday, a natural avalanche from Mt Herman ran down to the valley floor where it nearly hit a group of ski tourers as it reached across to the other side of the valley (see photo and video below).  Additionally, a large snowmobile triggered wind slab avalanche was reported in the Mt Baker area on Sunday.

    Some avalanches failed near the most recent crust, which is now buried 2 or more feet down.  Persistent weak layers near the crust may produce more reactive and larger avalanches than you think. The distribution of these weak layers is uncertain but keep this in mind as you travel in the backcountry on Tuesday.  

    Temperatures and snowfall intensity will reduce Monday night into Tuesday, but the avalanche danger will remain elevated for another day as the snowpack adjusts to such a large storm. The likelihood of avalanches will slowly drop throughout the day as the storm dissipates.  For now, find slopes less than 30 degrees and areas away from the runouts of avalanche paths to recreate on and travel through.  

    (1/29/2021) A skier triggered avalanche on a west aspect at 5300ft on Mt. Herman. The avalanche broke 1ft deep, 50ft wide, and ran a few hundred feet downslope. Photo: Pete Durr

  • Storm Slabs

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

    A fresh coating of snow will fall Monday night into Tuesday down to about 2000ft in elevation.  We are forecasted to receive up to a foot of new snow so be cautious of storm slab avalanches on slopes steeper than 35 degrees.  Damp snow beneath the new layer may act as a good sliding interface for avalanches to occur on. Follow the same advice as what was suggested above, by staying out of all avalanche terrain while this unsettled period winds down.   

    A D1 Soft Slab avalanche intentionally triggered below treeline in the Swift Creek Area on 1/30. Photo: Carleigh Garrett

Avalanche Discussion

Sticking to low angle terrain far away from avalanche paths is a great plan as we ride out this storm through Tuesday.  This week we've made up for the period of high pressure in the preceding weeks. Since Saturday the Heather Meadows weather station has recorded 7 inches of water, and there is about 3 feet of new snow above 5000ft.  For nearly the entire day on Sunday and Monday around a tenth of an inch of water was recorded every hour.  A tenth of an inch of water or more per hour is an indicator that the snowpack is rapidly being loaded, and oftentimes it means the snowpack cannot adjust quickly enough and, as a result, avalanches occur. Giving the snowpack a day to adjust after this sort of occurrence is wise. 

Rain at lower elevations on Monday may leave some residual wet snow avalanche concerns below treeline. Keep an eye out for glide cracks on steep slopes with smooth ground surfaces, such as rock slabs and grass. Avoid any signs of glide cracks as there is a small chance that glide avalanches may occur.  

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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