Avalanche Forecast

Professionals observing the Olympics from the air on Tuesday noted minimal small loose wet activity and nothing large. Most of the debris piles were older from loose dry avalanches last week. Warmer temperatures this week ended the loose dry activity.

On Thursday, we’ll be entering our 4th full day of near-freezing overnight lows and highs in the 40s. Thursday is likely to be warmer than Wednesday with few clouds in the afternoon. 

This has been a prolonged gradual warm-up and loose wet cycle. We really haven’t seen a widespread avalanche cycle yet, which would “flush” out lingering instability. 

Expect surficial refreeze to break down quickly Thursday morning as a strong March sun helps temperatures rise rapidly, softens the snow surface, and increases the avalanche danger. Pay attention to the snow surface. There’s a big difference between “soft” and “weak” snow. When you find more than 4” (ankle deep) wet snow on the surface, you’re moving into the weak and unstable zone. This could be your clue to seek out slightly firmer slopes on other aspects as the sun and the danger moves around the compass.

The snowpack has not transitioned to a spring-time state and cold layers and crusts still exist. As the warm weather drags on, you could see water percolating to these layers allowing for larger slabs or glide avalanches. Be leery of large complex sunny terrain during the hottest parts of the day. And remember that cornices, growing weaker in the sunshine, can act as a trigger even if you are on a cool, shady slope below.

Forecast Schedule

For the 2019-20 winter season, avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week, No Rating will be issued but forecasts will include expected conditions and relevant travel advice.  If you are out in the Olympics, share your backcountry observations.

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.