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RegisterJan 16th, 2020–Jan 17th, 2020
Olympics.
You can trigger large and dangerous wind slabs near ridgelines and particularly above treeline, where strong winds on Wednesday stripped exposed areas and deposited large amounts of cold, dry snow onto a variety of aspects. Near and below treeline, recent snow has layering but shows a trend toward increasing stability. Avoid steep rollovers such as (Sunrise Bowl and Mustang), particularly under recently corniced terrain and all slopes steeper than 35 degrees above treeline.
The snowpack nearly doubled at Hurricane Ridge since the last crust formed on January 7th. And below treeline, we now have a snowpack capable of producing avalanches with around a meter of snow sitting on the crust at most elevations. Several storm systems dropped 2.3” of snow water equivalent last Friday through Monday morning with significant additions of lower density snow on Tuesday night (when up to two ft of snow accumulated in Port Angeles, corresponding to 0.31” of snow water equivalent picked up at Hurricane Ridge). Snow started up again Wednesday afternoon with winds increasing and averaging 25-30 mph with gusts to 50 mph on Wednesday evening. The storm snow has been capped by a thin layer of lower-density snow.
With all the recent snow, deep snow hazards are real. Before heading out, learn about tree well or snow immersion suffocation risks and travel with a partner (www.deepsnowsafety.org).
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 with us and the greater community.
January 16th, 2020 (The regional synopsis is updated every Thursday @ 6 pm)
In the past week and a half, there have been five avalanche fatalities in three separate accidents in the US. One occurred near Kellog, ID and another outside of Baker City, OR. Local avalanche centers will perform accident investigations including final reports. You can find preliminary accident information at avalanche.org.
From January 9th to 16th the Pacific Northwest slid into deep winter. A cold and snowy regime brought a nearly continuous barrage of storms through the area. Temperatures bottomed out as modified arctic air made its way south from interior Canada, and many stations recorded the lowest temperatures of the season so far. A snowpack has been growing at lower elevations due to some lowland snow on both sides of the Cascades. NWAC’s snow depth climatology report shows most stations have surpassed average depths on the ground for this time of year. Quite the comeback from two weeks ago, when most were at 25-64% of normal.
Location
Total Snow Depth (in) 1/8/20
Total Snow Depth (in) 1/16/20
Hurricane Ridge
51
91
Heather Meadows Mt Baker
95
126
Stevens Pass
63
85
Snoqualmie Pass
33
77
Mission Ridge Mid Mtn
18
28
Crystal Mt Green Valley
66
92
Paradise Mt Rainier
105
138
White Pass Upper
69
110
Timberline
57
118
Mt Hood Meadows
53
98
Snow depths continued to rise. Total snow depths doubled in some locations.
The mountains went through a period of prolonged dangerous to very dangerous conditions as the snow kept coming. Many locations picked up over a foot of new snow per day for a number of days in a row, and storm slab instability was widely experienced across the region. At times, instabilities within new snow layers were very reactive, and you didn’t have to do much to provoke an avalanche. Many people triggered small to large soft slab avalanches, even well below treeline. The cold temperatures tended to preserve these instabilities longer than usual during this time.
Small ski triggered storm slab near Mt Hood Meadows. January 11, 2020. Scott Norton photo.
This cold, low density snow was also susceptible to wind drifting as westerly winds buffeted the alpine zone from the 8th to the 15th. On the 15th the mean winds shifted, and a south and east wind event disturbed the powder on open, exposed terrain near the passes and at upper elevations throughout the region. This created wind slab problems in some unusual locations.
Wind slabs formed over the low density powder snow. Mt Baker Backcountry. January 15, 2020. Zack McGill photo.
Trailbreaking in undisturbed snow was often very deep and difficult. In most places at any point in the week you could step off your skis or machine and sink in up to your chest in deep powder snow. The deep snow presented hazards of its own such as tree wells, and made it very easy to get stuck on a machine or lose a ski. Many folks experienced excellent, deep powder conditions and stuck to conservative terrain choices.
-MP
A cold winter’s day over the Chiwaukum Range, from Stevens Pass. Matt Primomo photo.