Avalanche Forecast
Issued: Mar 7th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
cgarritty,
Avalanche Canada
Start small and watch for signs of instability or indications that new snow has settled into a reactive slab over the old snow surface on Sunday. Expect new snow to become especially touchy on southerly slopes if the sun makes an appearance.
Summary
Confidence
Moderate - Forecast snowfall amounts are uncertain.
Weather Forecast
Saturday night: Cloudy with continuing flurries and up to 5 cm of new snow. Light to moderate southwest winds, becoming strong at ridgetop.
Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate southwest winds, becoming strong at ridgetop. Alpine high temperatures around -9.
Monday: Sunny. Light southwest winds. Alpine high temperatures around -8.
Tuesday: A mix of sun and cloud with cloud increasing over the day. Moderate to strong southwest winds. Alpine high temperatures around -4.
Avalanche Summary
Preliminary reports from Saturday in the neighbouring Lizard Range and Flathead mainly show new snow reacting to skier traffic and explosives control as dry loose sluffs, reaching size 2. Soft slab formation was noted in wind-affected features at ridgecrest. Similar conditions are expected to exist in areas of the South Rockies that saw 20 or more cm of new snow.
Elevated avalanche danger is expected to be maintained through Sunday as the new snow settles into more consolidated storm slabs that only gradually begin bonding with the previous snow surface. Periods of sunshine may also promote natural avalanche activity.
Snowpack Summary
By the time snowfall eases off Saturday night, new snow totals over the region may reach up to 30 cm. The new snow has buried recent wind slabs and wind effect in exposed terrain as well as sun crust on solar aspects and temperature crust up to 1700 m on all other aspects. The new snow is not expected to bond well with any of these surfaces over the short term.
A thick rain crust currently sits 40-80 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17. The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
Terrain and Travel
- Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
- Avalanche hazard is expected to to increase througout the day, think carefully about your egress.
Problems
Storm Slabs
20-30 cm of new snow is settling into storm slabs that are not expected to bond well with the previous snow surface. Wind has already been observed accelerating slab formation around ridgetop features. Snow may shed naturally as slabs or dry loose releases from slopes exposed to sunshine.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak snow at the bottom of the snowpack hasn't gone away, and will be an increasing concern as rapid loading and avalanches in surface layers strain the snowpack on Saturday. Evidence of deep persistent slab avalanches has been focused in the Sparwood-Elkford area over the past month. Human triggering is most likely around steep rocky terrain features, or anywhere the snowpack is thin and weak.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 8th, 2020 5:00PM
