Avalanche Forecast
Issued: Mar 15th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Persistent Slabs and Wind Slabs.
swerner,
Avalanche Canada
Spring-like conditions will persist through the forecast period. Natural avalanche activity will likely spike in the afternoon when warming and solar radiation destabilizes the snowpack.
Summary
Confidence
Moderate - Confidence is due to a stable weather pattern with little change expected. Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region.
Weather Forecast
A spring-like diurnal weather pattern is expected through the forecast period. This will bring rising freezing levels to 2000 m by the afternoon then falling back to the valley bottom overnight. No new snow is expected and mostly sunny skies will prevail.
Avalanche Summary
The warm weekend proved to show a widespread natural avalanche cycle primarily loose wet up to size 2 but natural cornice failures were reported as well as some wet slabs seen up to size 2 and potentially larger. Check out these excellent MIN reports from Saturday.Â
With warming and solar input continued, it might lead to deeper releases on the persistent weak layer this week.
Our field team found some large and disturbingly wide avalanches in the Hasler last Tuesday, with lots of compelling images in their MIN report here. It's suspected that these are running on facets that are about 80 cm below the surface.
This adds to the tally of recent large avalanches they started collecting in Pine Pass on Monday.Â
Snowpack Summary
The northern portion of the region around the Pine Pass has picked up 35 new cm as of Saturday afternoon but very little new precipitation has fallen in the southern 2/3 of the region. This snow is expected to be redistributed by the strong southwest wind and also felt the heat of the rising freezing levels over the weekend.
Sun crust exists on solar aspects and a temperature crust may exist on all aspects to 1800 m. Wind effect is widespread in the alpine and treeline across the region.
About a metre of snow covers a weak layer of facets buried mid-February. Slightly deeper there is a widespread persistent weak layer from late January/early February that consists of surface hoar. It is most prevalent around treeline elevations, but likely reaches into the alpine and in openings below treeline too. These layers are both significantly shallower in the east of the region.
Terrain and Travel
- Avoid avalanche terrain during periods of strong sun.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
Problems
Loose Wet
Loose wet avalanches are possible through the forecast period, especially on steep solar aspects. This problem will be amplified in the afternoon when the freezing levels rise and the sun is shining. With a solid overnight re-freeze, this problem will likely not exist in the morning. Pay close attention to warming and solar input. Moist snow is a good indication that the snowpack is heating up and destabilizing.
Cornice failure is likely as the strong mid-March sun and warming temperatures go to work. As cornices impact underlying slopes there is potential for them to trigger persistent slab avalanches.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
The persistent slab problem appears to have been put to rest in deep snowpack areas in the west of the region, but on the eastern slopes (e.g. Kakwa/Tumbler Ridge) there have been very large recent natural avalanches. The rising freezing levels last weekend combined with daytime warming this week may wake this problem up. The most likely triggers are surface avalanches stepping down, cornice fall, or the weight of a machine or a person hitting a thin-spot.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
This problem can be found in the north of the region in areas around Pine Pass where up to 35 cm of new snow fell accompanied by strong wind by Saturday morning. Wind slabs may be resting on a sun crust on solar aspects which could allow avalanches failing to run further and faster than you'd normally expect.
Aspects: North, North East, East.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 16th, 2021 4:00PM
