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RegisterFeb 27th, 2018–Feb 28th, 2018
Olympics.
Stormy conditions will create dangerous Wind Slab avalanche conditions by Wednesday afternoon. Step back your terrain selection as you observe signs of snow transport and avoid steep lee slopes. It is still be possible to trigger a dangerous Persistent Slab avalanche. Stay away from large open slopes steeper than 35 degrees that are suspect for these avalanches.
Increasingly stormy conditions will develop in the Olympics on Wednesday with winds increasing to strong by late afternoon. These winds will create the potential for large and reactive wind slabs near and above treeline, particularly on Wednesday afternoon and the wind slabs will extend into exposed near treeline terrain.
The persistent slab problem remains a concern, though reports from the WA Cascades indicate it is very gradually healing, but still showing propagation potential in snow tests. Weak sugar-like facets can be found just above a firm crust layer formed in early February on all but south aspects. This layer is down about 2-3 feet, shallow enough to be human triggered. Observations on the distribution and sensitivity of this layer can be difficult to gather. When uncertainty increases, safe terrain choices decreases. Avoid steep open slopes where a persistent slab avalanche may occur. Another potential persistent weak layer may have developed on W-SW-S-SE-E aspects with facets on a crust and will be something to watch as the Wednesday's storm loads the upper snowpack.
Calm and cool conditions Monday and Tuesday with sun breaks allowed for storm layers deposited over the weekend to mostly settle and stabilize.
An active storm cycle began Friday evening. By Monday morning about 2 ft of new snow had accumulated in the Hurricane Ridge area. The most recent snow Sunday fell with slightly warmer temperatures and was easily transported by winds depositing fresh wind and storm slabs on weak low density snow deposited by early Saturday.
About 3 or more ft of of settled snow sits on top of the weak sugary facets that formed on a strong crust earlier in February. Snowpack tests continue to suggest that these facets can fail and produce avalanches. This layer has not been reported on South aspects in the Hurricane Ridge area.
There are no other significant layers of concern in the mid and lower snowpack.
Dangerous avalanche conditions developed Sunday contributing to avalanches that claimed 3 lives in two separate accidents near Snoqualmie Pass. NWAC field staff traveled to both accident sites to investigate the avalanches in preparation for forthcoming accident reports. Our condolences go to the friends and families of the victims.
A very large natural avalanche crossed Highway 20 east of Newhalem on Sunday.
Observations
NPS ranger Monday morning reported the most recent 9 inches of new snow at Hurricane Ridge had surprisingly little wind effects and was low cohesion.
Sunday, NPS rangers indicated the additional new 8 inches of snow was stiffer and more cohesive, being deposited over the previous days weak snow.
On Saturday morning, NPS rangers reported that 8 inches of new storm snow had low cohesion with little wind effects noted and no slab structure.
On Thursday Matt Schonwald and NPS rangers observed 20-30 inches of generally right-side-up surface snow over weaker snow (facets). Snowpack tests indicated the weak facet layer could still fail and produce avalanches. Northeast winds during the day Thursday redistributed snow onto SW-W-NW aspects.