Avalanche Forecast

A winter storm will begin to impact the Snoqualmie area Friday but shouldn’t create any significant avalanche hazard during the day. Cold temperatures, light winds, and only 3-5” of new snow should limit slab development and any avalanche concerns. Even though the avalanche danger is low, you may see the hazard very slowly creep up late in the afternoon. If more snow falls than expected or the winds begin to transport snow during the day, you could see slightly higher avalanche danger. There are two primary avalanche issues you should have on your mind Friday if you travel in the mountains. 

• Loose Dry: The new snow may not bond well to the old surface, and you should expect it to sluff on steep slopes and produce small loose avalanches. Even though these slides shouldn’t pose much risk, don’t let them surprise you, especially in higher consequence terrain. 

• Wind Slabs: The winds are expected to increase late in the day and this could begin to drift snow into very small isolated pockets. Be leery of smooth wind pillows in areas where losing your feet would have big consequences. 

Avalanche professionals around Snoqualmie Pass this week reported a wide variety of snow surfaces including very frim crusts, wind stiffened snow, hard icy rime, weak facets/surface hoar. and even settled soft powder. As the new snow falls on this smorgasbord of old surfaces, expect the snow to respond differently slope-to-slope.

March 12, 2020 (The regional synopsis is updated every Thursday @ 6 pm)

From March 6th to the 12th the Pacific Northwest experienced a few small storms and a few notable days for people and avalanches. Light to moderate snow accumulated slowly over a period of a few days, and avalanche danger increased from Low to Moderate over the weekend of March 8th. The exception was the West North zone, which won the snowfall competition this week. 18-24” of new snow was observed in the Mount Baker area on the 6th, and 10” of new snow on the 11th. Avalanche danger reached Considerable there for storm slab, wind slab, and loose wet avalanche problems. 

People, complicated avalanche terrain, and lots of avalanches. Bagley Lakes Basin, West North zone. Photo by Nathan Resick, March 8, 2020.

Loose dry slides initiated by skiers in big terrain. No one was caught or carried. East Central zone. March 8, 2020. Matt Primomo photo.

The snow fell with minimal wind, and accumulated slowly over firm suncrusts or wind stiffened surfaces. Thicker cloud cover inhibited the sun in areas where 4” to 12” of snow accumulated over the course of a few days. Cold overnight temperatures allowed the low density snow to weaken. By the 8th, the clouds broke up enough to allow strong radiation to change snow surfaces. When the sun finally did hit the snow, it quickly caused loose avalanches in steep terrain. 

An active weekend for people and avalanches: 

Many areas experienced some form of loose avalanche activity from March 6th to 9th.  Sunday, March 8th was the day that recorded the most widespread avalanche activity across the region. The size of these avalanches were directly related to the amount of new snow that had recently accumulated in that area, and the size of the terrain. 

West North zone on March 8, and West South zone on March 8th. Uphill and downhill tracks got covered by debris. Photos by Zack McGill and Dallas Glass.

We as a community can look back at, and learn from these few days. Numerous human triggered slides occurred, some were slabs but the majority were loose. A number of catch and carries were observed, and many more likely went undocumented. Luckily, no injuries or burials were reported. Observers across the region reported lots of instances where previous tracks got hit with debris, either from human triggered or natural avalanches. 

As the days get longer and folks begin to step into the alpine zone and bigger terrain more frequently, it is important to keep a humble attitude. Continuously evaluate route selection with potential for loose wet and cornice falls in mind. Check the mountain weather and avalanche forecasts for the most up to date info. Enjoy the backcountry, be safe, and let us know what you see out there!

-MP

Solo snowboarder aired into this slope, and went for a ride but was not buried or injured. Slide took out the corner of a skin track. Bagley Lakes Basin, March 8, 2020, Zack McGill photo.

Wind slab triggered by a skier at 7,500ft next to the popular route on Mt St Helens. The skier wasn’t caught or carried. Andy Goodwin photo, March 8, 2020.