Snoqualmie Pass

The little bit of rain and snow expected at Snoqualmie Pass on Sunday shouldn’t create much in the way of avalanche danger. The greatest hazard you face could come from variable and often icy travel conditions. Don’t let a slip turn into a longer fall especially above creeks and cliffs.

A storm arriving Sunday will finally bring an end to this prolonged period of warm and dry weather. However, we aren’t expecting much in the way of rain and snow before the end of the day. So, we’ll mainly be left with cloudy skies, increasing winds, and cooler temperatures. This should keep the snow frozen and all but eliminate any avalanche hazard. By the end of the day, a few inches of snow may accumulate at mid and upper elevations around the Pass. If more snow falls than expected or if you find wind-loaded terrain you might encounter thin isolated wind slabs. These pockets of wind drifted snow might trigger very easily, but their small size should keep them from posing much of a risk. As the storm intensifies Sunday night and Monday, expect that to change. Snow totals will grow and with it the size of any avalanches. This may create dangerous conditions by Monday morning.  

This new snow will fall on a variety of surfaces. Over the last few days, NWAC forecasters and avalanche professionals traveling in the Snoqualmie area reported very firm and icy crusts, sugary near-surface facets, weak surface hoar, and facet-crust sandwiches. “Variable” seems to be the word most often used to describe the snow. Above the rain-snow line, the new snow may struggle to bond to these variety of surfaces. As a result, you may see small sluffs or even very thin slabs fail as snow begins to accumulate. In general, icy melt-freeze crusts exist at lower elevations and on SE-SW aspects above 4000’. Near-surface facets and facet-crust sandwiches were found on NW-NE aspects at mid and upper elevations. While this pattern typically holds true, the highly variable snow surface prior to this storm will make predicting how any particular slope may react incredibly difficult. The good news is, as we move forward, the current surface should become the “new ground.” We expect avalanche concerns to stay near or above this interface. In the short term, that should make observing these possible weak layers very easier.

While the new snow should eventually help improve travel conditions, this will take time. Many travelers reported slick and icy snow over the past several days. This will still pose a significant risk on Sunday. Make sure you have the skills and tools you need to safely navigate these tricky slopes.