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RegisterFeb 28th, 2018–Mar 1st, 2018
Olympics.
Significant uncertainty exists in the Olympics right now so it is a good time to make conservative terrain choices. You may trigger fresh, reactive wind slabs at all elevations on Thursday. You might also trigger a persistent slab yourself or by initiating a wind slab avalanche. Reduce your hazard by traveling in terrain less than 35 degrees, avoiding wind loaded open slopes, and avoiding terrain exposed to overhead cornice hazard.
Moderate to strong southerly winds will continue to build wind slabs at all elevations on exposed lee slopes. The storm will move new snow in addition to the older low cohesion snow observed Monday. Given the strength of the winds, these slabs may be large and are likely to be reactive.
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 or triggered by a wind slab stepping down to the weak layer. Observations on the distribution and sensitivity of this layer can be difficult to gather. When uncertainty increases, safe terrain choices decreases. Stay safe by avoiding locations where wind slabs might trigger, steep open slopes where a persistent slab avalanche may occur, and terrain threatened by cornice fall. 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 we gather more information following this storm.
Due to a lack of recent observations and a complicated snowpack, this is a good time to make conservative terrain choices.
On Wednesday afternoon, light snow fell along with moderate southerly winds with strong gusts were that were more than capable of moving significant snow and forming fresh and reactive wind slabs.
Cool and dry conditions Monday and Tuesday with sun breaks allowed the storm layers from last 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.
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 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.