Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

An incoming storm will start to build a fresh crop of wind slabs throughout Saturday. Shifting winds could cause slabs to form on both sides of the same ridge. Be leery of steep slopes where you find firmer pillow-like slabs.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Winds will start to increase and shift out ahead of this storm. This will help drift some of the soft surface snow into new slabs. As the snow starts to fall, it will only make this process easier. So, if you start to see signs of wind-affected snow down low, expect the problem to become more widespread and more dangerous as you ascend. 

    Because the winds will shift from SE to SW during the day, actively blowing snow may not always tell you where the wind slabs are/are not. You’ll need to keep your eyes open and look for textured surfaces and firm pillow-like drifts. While these slabs should be small, they could fail easily and may even break above you. Give them a wide berth in high-consequence terrain.

    (3/1/2024)

    A small natural wind slab avalanche on Snow Lake Divide: SE, 4900ft. Note the other picture with a similar slide on the opposite side of the ridge. 

    Photo: Trevor Kostanich

Avalanche Discussion

NWAC is devastated to report the death of one of our Avalanche Forecasters, Matt Primomo. Tragically, Matt passed away in a non-avalanche accident away from work on Thursday, March 7th. Matt has been a key member of the NWAC family since 2017. His life in the mountains touched so many people. We are absolutely heartbroken. Please join us as we mourn this immense loss with Matt’s family, friends, and community.

Discussion:

The first in a series of storms will impact the Pass Saturday. It will take a bit before enough new snow piles up to really increase the avalanche danger. However, there’s still some soft snow left to blow around. A remotely triggered wind slab avalanche on Mt Snoqualmie Friday also begs the question of fresh wind slabs forming over unstable surfaces like surface hoar/facets on northerly aspects and firm crusts on southerly slopes. If that’s the case, these small slabs may be quite touchy. 

Over the past few days the snowpack became very aspect dependent. Southerly aspects formed a new crust. How thick and strong this layer is depends on elevation, aspect, slope angle, and location in the zone. On shaded slopes, cold clear nights helped develop surface hoar and smaller near surface facets. These weak grains may survive in wind sheltered areas going into this storm. If you’re out before the snow falls, take note of what’s on the surface, and let us know what you see. There’s the old avalanche adage, “today’s surface is tomorrow’s weak layer.”

Below the surface, several feet of well settled right-side-up powder exist. This caps some older, weaker layers that formed during February. While we haven’t seen recent avalanches on these persistent weak layers in the Snoqualmie area, other nearby forecast zones (East Central, Stevens, West South) have been plagued by persistent slab problems for the past week. Keep this issue in mind if you head to more remote areas particularly further east in the zone. 

Rain and wet heavy snow could produce some very small wet loose avalanches at lower elevations. These shouldn't be very large and shouldn’t pose much of a threat.

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