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RegisterFeb 26th, 2020–Feb 27th, 2020
Northwest Coastal.
We're expecting a widespread natural avalanche cycle to continue through Thursday night as each 12-hour period ushers in another 10 to 20 cm of snow accompanied by strong southwest wind. Avoid all avalanche terrain at this time.
The storm rages on...
WEDNESDAY NIGHT: Freezing level around 1200 m, strong southwest wind, 10 to 20 cm.
THURSDAY: Overcast, freezing level holding around 1100 m, strong southwest wind, 10 to 30 cm of snow with another 5 to 15 cm Thursday night.
FRIDAY: Broken cloud cover, freezing level holding around 900 m, moderate southwest wind in the morning, light variable wind in the afternoon, 1 to 5 cm of snow.
SATURDAY: Clear skies, freezing level holding around 1000 m, light variable wind, no snow expected.
We're short on observations that depict the change in conditions since the storm entered the forecast area, but a natural storm slab avalanche cycle is likely in progress and is expected to continue through Thursday night as a significant amount of storm snow and wind impact the region.
On Tuesday there were reports of very large wind slabs in the Bear Pass zone from steep alpine features. Small storm slabs were also sensitive to natural and human triggering from steep terrain. As snowfall picked up Tuesday night there were audible loose snow avalanches from steep terrain too.
On Monday in the Ningunsaw zone a natural cornice failure resulted in a very large (size 3.5) deep persistent slab avalanche on a south/southeast facing feature. Another large cornice failure was also noted.
On Sunday a few different observations of the avalanche cycle that occurred during (Feb. 21) and just after the last storm emerged. Natural avalanches were widespread to size 2.5 at all elevations, likely running on facets and surface hoar.
Glide crack openings and failures continue to be reported (almost daily) too.
15 to 30 cm of new snow fell Tuesday Night into Wednesday and significantly more snow is expected in the next 24 hours. Widespread natural storm slabs are forming and there is likely a natural avalanche cycle in progress.
This snow adds to the 50 to 80 cm of storm snow that the last storm left in it's wake. There is potential for "step down" avalanche activity as the fresh snow interacts with "old" storm slabs that overly a couple layers of surface hoar that may be found in sheltered terrain at and below treeline or a melt-freeze crust on sun-exposed aspects.
A thin layer of weak and sugary faceted grains that formed in January may be found about 120 to 170 cm deep, and an early-season melt-freeze crust lingers at the base of the snowpack. These layers produced a few large natural avalanches in early-February and were largely nonreactive until the Feb 24th avalanche listed above was reported. This kind of storm has the potential to produce some very large avalanches as the snowpack is rapidly loaded.