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RegisterMar 20th, 2018–Mar 21st, 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 over the past month.
Low Danger means that triggering avalanches is unlikely but not impossible. While Deep Persistent Slabs are very difficult to trigger, the resulting avalanche could leave little chance of survival. 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 are still present, though getting harder to trigger. 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.
Avoid traveling near or under areas with glide cracks and stay away from large cornices. Increasing cloud cover should limit the potential for Loose Wet avalanche activity on Wednesday.
Expect mild temperatures and increasing high cloud cover on Wednesday. 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 stout crusts in the top foot of the snowpack. At Mt. Baker, 6 inches of snow accumulated Wednesday, which quickly melted on sunny slopes. Mid to upper 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 are good for demonstrating the presence of a weak layer, they are not a decision-making tool to 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.