Avalanche Forecast
Issued: Mar 10th, 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 recent storm was a big one and the snowpack may take longer than usual to recover, especially given the presence of persistent weak layers. Choose conservative terrain and minimize overhead exposure to avalanche terrain as the potential still exists for large avalanches.
Summary
Confidence
Weather Forecast
TUESDAY NIGHT- Mainly cloudy with flurries, 5-10 cm / west wind, 30-60 km/h / alpine low temperature near -8
WEDNESDAY- Cloudy with sunny periods and isolated flurries / west wind, 40-60 km/h / alpine high temperature near -8
THURSDAY- Cloudy with sunny periods / northwest wind, 20-30 km/h / alpine high temperature near -9
FRIDAY- Sunny / northeast wind, 30-60 km/h / alpine high temperature near -9
Avalanche Summary
Avalanche activity is expected to continue on Wednesday with the likelihood of both natural and human triggered avalanches remaining elevated. Due to the presence of a recently buried surface hoar layer, avalanches may be especially easy to trigger in the trees, where the layer is likely preserved.
It is suspected that a widespread natural avalanche cycle occurred on Monday night and throughout the day on Tuesday.
On Monday during the day, there was a report of a human triggered size 2 persistent slab avalanche on a north aspect at about 1200 m. This avalanche was about 50 cm deep and it is suspected that it ran on a layer of buried surface hoar.
Snowpack Summary
The storm on Monday night and Tuesday delivered 30-50 cm of new snow to the region with strong southwest 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 will be widespread and will likely 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 layer of weak and sugary faceted grains 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.
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 produced large natural and human triggered avalanches as recently as Friday. They are most problematic at shaded treeline elevations where the surface hoar is well preserved.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 11th, 2020 5:00PM
