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RegisterMar 18th, 2018–Mar 19th, 2018
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Low Danger does not mean no danger. Continue to use normal travel practices. Deep Persistent Slab avalanches are very difficult to trigger, but the potential for high consequences lurks deep in the snowpack. Weak layers buried deep in old snow have been responsible for fatalities and serious injuries each of the past four weekends.
Low Danger means that triggering avalanches is unlikely but not impossible. While Deep Persistent Slabs are very difficult to trigger, the resulting avalanche could be so large and destructive that you will have little chance of surviving. Persistent weak layers have been the cause of avalanche fatalities or serious injuries every weekend for the past 4 weeks. Recent test results and avalanches show that these layers can still be triggered. Currently, you will see significant backcountry traffic in avalanche terrain, but little signs of avalanches. The best way to stay safe from the potential consequences is to limit your exposure to large avalanche paths. Stay out of start zones and large, complex avalanche paths.
Until southerly slopes get softened by the sun they will remain hard and slick. If you travel on these slopes while they are still firm it may be difficult to stop a fall. Avoid traveling near or under areas with glide cracks and stay out from under large cornices.
Expect cool temperatures and a mix of sun and clouds for Monday. If the sun comes out, it could soften the surface of sun-exposed slopes. While there may be a few rollerballs in areas that received a couple inches or more of recent snow, Loose Wet Avalanches should not be a problem. A dusting of light snow on Saturday and Sunday followed a warm, sunny stretch at the end of the work-week. Many sunny slopes have very hard crusts in the top foot of the snowpack. At Mt. Baker, 6 inches of snow accumulated Wednesday, which quickly melted on sunny slopes. High elevation, northerly slopes are staying soft and dry.
Below this most recent crust most observations indicate strong layers of dry snow intermixed with various melt freeze crusts. A more widespread deep persistent layer continues to be found 5-7 feet below the snow surface in the Mt. Baker zone. A thin layer of weak sugary facets have been observed just above a stout crust (2/8) on some aspects. Some snowpack tests (Compression Test and Extended Column Tests) will not be able to appropriately assess this deep weak layer. Deep Tap tests and Propagation Saw tests will yield the most reliable results. While snowpack tests may demonstrate the presence of a weak layer, they are difficult to interpret and are not a good tool for determining whether or not a slope is safe.
Observations
Baker
On Saturday, NWAC Observer Matt Primomo reported a large glide avalanche on a rock face on the south aspect of Mt Herman. The slope is known to commonly produce glide avalanches during warm conditions.
NWAC professional observer Lee Lazzara traveled to Ptarmigan Ridge Friday. New and recent wet loose avalanches, generally small, were visible on steep sunny slopes. Older wind slab found near and above treeline was unreactive. A thin sun crust from Thursday had extended it's reach to W-NW aspects. The 2/8 layer was down 6 feet in this area.
Lee was near Glacier Creek Thursday and found 3 to 8 inches of new snow well bonded to a forming melt-freeze crust. The 2/8 layer was down 6 feet in this area.