Avalanche Forecast

Issued: Mar 12th, 2020 11:00AM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

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Snowy weather will begin to impact the West-South zone Friday, but shouldn’t bring enough new snow to pose any significant avalanche risk before the end of the day. Even still, the new snow may not bond well to the old surface and you could produce sluffs on steeper slopes.

Summary

Discussion

A storm system will begin to bring new snow to the West South zone Friday, however, we don’t expect enough new snow during the day to create any meaningful avalanche risk. All locations are expecting between 3 and 5 inches by late tomorrow afternoon. This snow should fall with cold temperatures and light winds which would limit any slab development and avalanche issues. The biggest concern may be how this new snow bonds to the old surface. The storm snow will accumulate on a wide variety of surfaces including firm crusts, wind packed snow, icy rime, and dry settled powder. This could cause the new snow to react differently from slope-to-slope. We don’t expect the new snow to bond well to these old surfaces. As a result, you may trigger small loose avalanches on steep slopes. Don’t let these sluffs catch you off guard especially in high consequence terrain. 

Even though the avalanche danger is low, as more snow piles up you could see the avalanche danger very slowly creep upward. If more snow falls than expected or the wind begins to drift the snow into sizable slabs, dial back your terrain use and avoid wind loaded pockets on steeper slopes. Expect more snow Friday night to increase the avalanche danger going into the weekend.

Snowpack Discussion

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.

Valid until: Mar 13th, 2020 11:00AM