Avalanche forecast

West Slopes Central

Northwest Avalanche Center
View on map

Avalanche danger

Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
Open full map
Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A storm is forecasted to bring over a foot and a half of snow to the zone by the end of the day. Avalanche danger will increase as more snow falls, and especially during periods of higher snowfall intensity. As the day progresses, dial back your terrain selection, avoiding steep slopes and possibly steering around lower-angle terrain below steep slopes, especially at upper elevations. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    New snow and wind are a great recipe for avalanches. We're forecasted to get about 6 inches overnight and over a foot during the day. If we get more or less snow than forecasted, conditions may be different than forecasted.  Avalanche danger may start lower, but will increase as more snow falls. When the snow is falling at faster rates, you can expect more avalanche activity. Natural avalanches could result. At higher elevations, more wind will likely result in increased avalanche activity. 

    At first, shallow avalanches may be limited to wind slabs, but when the snow gets a little deeper, the distribution will likely expand to any deposits deeper than 6 inches, wind-drifted or not. Dial back your terrain selection as the day progresses. Maybe you can start the day on steep slopes, but once snowfall amounts are greater than 6 inches, avoid slopes greater than 30°. As the new snow layer grows deeper than a foot, if it's actively wind loading, and especially if you notice any natural avalanche activity or identify any other red flags, take another step back and avoid lower-angle terrain beneath large, steep slopes.  

    Example photo: a storm slab avalanche failing naturally on a steep slope, similar to what you might see on Wednesday. 

Avalanche Discussion

For several days we've been discussing a buried weak layer that we know very little about. The layer of concern is mainly at upper elevations, and no human-triggered avalanches have occurred on the layer. A few large avalanches that may have failed on the suspect layer above the 12/30 crust have been reported in neightboring zones. The layer is probably buried 3 to 5+ feet deep, so a person probably wouldn't trigger an avalanche on the layer. With the new storm snow, there's a small chance some very large avalanches may occur on large, unsupported upper-elevation slopes, failing down to this weak layer. 

An irregular patchwork of snow exists on the surface beneath the incoming storm snow. Very cold temperatures since the last storm have resulted in weak snow developing on and near the snow surface in areas that hold light, fluffy snow. Strong winds redistributed some snow into stiff and stubborn slabs. Once the new snow falls it'll be tough to identify what the old snow surface was like, so you may experience drastically different avalanche activity and bonding between the new and old snow layers, which might just be in a matter of feet. One slope may behave differently from the slope next to it. Even on the same slope, some pockets could behave differently from others. You can dig down to the new/old snow interface to identify bonding and use small test slopes, but they may not be representative a few feet away. 

If you get into the backcountry let us know what you found! Submit an observation HERE. 

Regions covered