Avalanche Forecast
Issued: Feb 26th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Cornices.
ghelgeson,
Avalanche Canada
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.
Summary
Confidence
Weather Forecast
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.
Avalanche Summary
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.
Snowpack Summary
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.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- Only the most simple non-avalanche terrain free of overhead hazard is appropriate at this time.
Problems
Storm Slabs
Continued snowfall and wind adds to an already serious avalanche problem. By Thursday morning up to 50 cm of new snow and 60 cm of older snow (for a total of over 100 cm) may be resting on well-preserved surface hoar at and below treeline. This kind of setup could open the door to a situation where it "goes electric" as deep avalanches run naturally in sheltered terrain at and below treeline. Even deeper slabs are expected in the alpine as strong southwest wind continues to build thick wind fuelled storm slabs. Solar aspects (those that face south and west) have a buried crust that could serve as a bed surface for very large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are most prone to failure while they're growing, and we're expecting continued strong southwest wind along with a significant amount of snow. When large chunks of cornice fail there is potential for deep slab avalanches as evidenced by recent activity.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 27th, 2020 5:00PM
