Avalanche Forecast
Issued: Mar 11th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
kdevine,
Avalanche Canada
The storm and associated natural avalanches have tapered off to some degree, but give the snowpack some time to adjust to recent loading as the new snow sits on a weak layer that will likely need more time to gain strength.
Summary
Confidence
Weather Forecast
WEDNESDAY NIGHT- Cloudy with clear periods and isolated flurries / northwest wind, 20-30 km/h / alpine low temperature near -8
THURSDAY- A mix of sun and cloud / northwest wind, 20-30 km/h / alpine high temperature near -7
FRIDAY- Sunny / northeast wind, 30-60 km/h / alpine high temperature near -10
SATURDAY- Sunny / northeast wind, 40-80 km/h / alpine high temperature near -10
Avalanche Summary
Avalanche activity is expected to taper off to some degree now that the storm is over and temperatures are dropping. However, the new snow rests on what may be a problematic weak layer of surface hoar in many areas and so the new snow may continue to be reactive for longer than usual.
The recent storm brought about a widespread natural avalanche cycle in the region over Monday and Tuesday. There were reports of numerous natural, explosives, and human triggered avalanches up to size 2.5.
Snowpack Summary
The recent storm delivered 30-60 cm of new snow to the region with strong winds. The new snow is sitting on a weak layer of surface hoar in many areas, especially in sheltered areas at treeline and below treeline. See this recent MIN post from the Shames area that shows this layer when it was on the surface.The new snow will also be sitting on a crust on solar aspects (south through west facing slopes). Fresh storm slabs are likely widespread and may take longer than usual to gain strength due to the presence of the weak layers that were buried in the recent storm.
There are two more layers of surface hoar that are now buried 70-120 cm, and 110-160 cm deep, and are likely the most prominent around treeline. On south through west facing slopes, this surface hoar may be sitting on a crust, which may increase the potential for triggering avalanches on these layers. Below about 1000m, the recent new snow is sitting on a melt-freeze crust.
A weak layer of facets that formed in January may be found about 150 to 200 cm deep, and an early season melt-freeze crust lingers at the base of the snowpack. These layers have produced a few very large natural and explosive triggered avalanches over the past two weeks.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Use small low consequence slopes to test the bond of the new snow.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Storm Slabs
Widespread storm slabs formed during the storm on Monday/Tuesday. These slabs are sitting on a weak layer of surface hoar in many areas and may still be easily triggered by humans. The surface hoar is most prominent at treeline and below treeline.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Two surface hoar layers are found 70-120 cm and 110-160 cm below the surface. These layers continue to produce natural and human triggered avalanches. They are most problematic at treeline elevations where the surface hoar is well preserved.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 12th, 2020 5:00PM
