Northwest Avalanche Center NWAC, Northwest Avalanche Center

Olympics Avalanche Forecast

Mar 16th, 2020 11:07AM

Expect a loose wet avalanche cycle to continue in the Olympic Mountains where temperatures shot above freezing early Monday morning and won’t look through Tuesday. Some cloud cover will battle the warm temperatures to limit activity. Avoid the generally small avalanches by reducing your exposure to steep sun-affected slopes, adjusting your aspect as the snow surface becomes moist or wet.

Summary

Discussion

The Olympic mountains picked-up 6-8” of light fluffy snow on Friday. This snow accumulated on a wide variety of surfaces including firm icy crusts, wind packed snow, old powder, and even weak facets. You may find that the snow reacts differently from one slope to the next. 

A skier triggered a shallow, 20 ft wide avalanche on the 20th of June on Sunday.

Temperatures stayed cold at Hurricane Ridge on Sunday due to Fraser outflow, but warmed drastically late Sunday night and reached the mid-40s on Monday. With a shallow overnight refreeze expected Monday night, the crust may break down early on Tuesday with continued warmth and sunshine early in the day. Cloud cover arriving by mid-morning may limit the size and distribution of avalanches. Check for wet snow you can sink in past your ankle to know that you need to adjust your aspect. Avalanches will be largest on long steep slopes where they can accumulate more of the shallow recent snow above the last crust.

With several days of warm weather, cornices are sagging and may fail at any time and they could trigger wet avalanches on the slopes below.

On northerly aspects, you may still find colder dry snow, which may become slightly stickier and denser as the snow warms. This reduces the risk for loose dry avalanches but creates a slight risk of slab avalanches if you find denser snow overlying a crust.

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.

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 17th, 2020 11:07AM