Avalanche Forecast

A break in the weather Saturday, will allow the avalanche danger to decrease slightly. You are most likely to encounter avalanche hazard at higher elevations where some of the recent precipitation fell as snow.

A few big stories stand out in the current snowpack: recent avalanche warnings in the northern zones, persistent slabs in the western areas, and a complex and weak snowpack in the eastern zones.

The northern zone experienced the brunt of this latest weather system. This led to two days of avalanche warnings and at least one large natural avalanche cycle. It's tough to say what the snowpack looks like in areas near and above treeline, but we know those areas received substantial new snow.

Earlier in the week we began forecasting a new persistent slab in our west-slope zones. A layer of buried surface hoar produced avalanches last Saturday, Sunday, and Monday. How did that layer fair after this recent round of weather? In locations like Mt Baker and Paradise, it was well tested with heavy precipitation. In other locations, less water may not have adequately stressed the weak layer. As visibility improves and more observation come-in the picture may become more clear.

In the eastern zones a complicated and weak snowpack exists. Several persistent weaklayers have plagued these regions most of the winter. Don’t expect this to change anytime soon. Snow profiles and snowpack test can give you a glimpse into the persistent layer. Remember, snow profiles cannot prove the absence of a weak layer or that a layer has “healed.”

An elongated open trough extends southward to the northern California coastal waters. The trough approaches the Pacific Northwest on Saturday afternoon with rain and snow spreading into the Olympic Mountains and southern Washington Cascades Saturday afternoon. This band of rain and snow will lift northward during the evening hours.

Saturday night will feature a wind storm. Strong southerly winds ahead of the rotating trough will be accompanied by moderate to strong easterly flow through the passes. Temperatures will be borderline for snow at Snoqualmie Pass. Once the surface trough passes, the flow will shift westerly and strong westerly winds will buffet the mountains in the early morning hours, bringing sharp cooling. Precipitation will be light to moderate in most locations, becoming snow showers after midnight and continuing Sunday in the unstable cold air behind the trough. Expect 7-14 inches of snow by the end of the day on Sunday for the Cascade volcanoes with the passes and Crystal picking up 2-6". 

Light snow showers will continue Sunday night into Monday, mostly confined to the west slopes of the Cascades. Snow levels will remain well below pass level. A ridge building late Monday will generally cut off the moisture from south to north.