Avalanche Forecast

Archived

Feb 9th, 2019–Feb 10th, 2019

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Snoqualmie Pass.

This recent snow is very light, dry, and unconsolidated. You are most likely to trigger avalanches in areas affected by the wind. Avoid open slopes greater than 35 degrees where you see drifted snow, uneven snow surfaces, or fresh cornices.

Discussion

Snow and Avalanche Discussion

The Snoqualmie Pass area received 12-14” of very light, dry snow Saturday. This new snow fell at very low temperatures and resulted in very low density, blower powder. Normally, with snow totals like this, you’d expect more avalanches. That wasn’t the case, and the forecasted avalanche danger did not materialize. Observations from the Alpental Valley reported a few natural small loose dry avalanches and very shallow soft slabs.

How is this snow going to change tomorrow? And how will that affect the avalanche danger? Tough to say. We’re worried about the recent snow settling. When this happens, the avalanches could become more likely. There are two things ways we could see snow settlement: 1: Time and 2: Sun. Both could be at play on Sunday. This pattern may run contrary to our normal northwest regime, where settlement often means stability. Avalanches may become easier to trigger Sunday. Keep your eye on slopes receiving direct sunshine. Even with these cold temperatures, the sun may create just enough settlement in the snow to create a slab.

Don’t forget, this recent snow is sitting on a weak layer of sugary facets and surface hoar. So far, we haven’t heard of any avalanches on this old snow layer. That may be because the new snow hasn’t formed a slab. Like we just talked about, that could change Sunday. If you see natural slab avalanches, experience sudden collapses, or see long shooting cracks, avoid nearby avalanche terrain.

Snowpack Discussion

New Regional Synopsis Coming Soon

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.