Lawinenlagebericht

Stevens Pass

Mar 17 – 18, 2020Northwest Avalanche Center
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Archiviert · abgelaufen 7 years ago

Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Expect minimal avalanche danger first thing in the morning, but as the daytime warms up the potential for avalanches will increase. Minimize your time, or avoid routes that expose you to overhead hazards from cornices and loose wet avalanches later in the day. 

Lawinenprobleme

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    Cornices are large and may begin to fail naturally after a few nights of above freezing temperatures at upper elevations. Look for these features and aim to avoid their potential runout. Large cornice collapses could trigger wide slab avalanches below.

    You may still be able to trigger wind slab avalanches in upper elevation shaded terrain, especially in the eastern edge of the zone where more snow fell over the weekend. Strong northeast winds drifted snow as recently as Sunday. Steer around obviously loaded slopes over 35 degrees where you see deeper drifts and pillows of snow. Avoid typical trigger points like convex rollovers and unsupported slopes. Watch for shooting cracks and whumphing collapses as indicators that you could trigger avalanches on nearby steep slopes. 

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    As the daytime warms up, expect to be able to trigger loose avalanches on steep slopes. Wet activity could start on northeasterly aspects early in the day and move to westerly aspects by afternoon. Watch for wet, punchy snow on south facing slopes or moist, sticky snow on shaded aspects as indicators. With very warm temperatures and full sun, loose wet slides could begin to gouge into deeper layers. Be sure to consider what is above you. Terrain features such as couloirs and gullies tend to catch sun that may cause shedding even if you are on a shaded aspect below. Use extra caution in and under these features.

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.

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