Avalanche Forecast
Issued: Apr 23rd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Loose Wet and Cornices.
swerner,
Avalanche Canada
Up to 30 cm of new snow is forecast for upper elevations by Sunday. New and reactive storm slabs may build at treeline and in the alpine.
This is the last forecast of the season.
Summary
Confidence
Weather Forecast
A weather system will approach the BC coast today. Tonight, the system will pivot towards the southern half of BC. The system will stall over southern BC tonight through the weekend resulting in persistent rain showers and alpine snow. The convective nature associated with this system could bring higher localized precipitation amounts.
Friday Night: Mostly cloudy with some isolated flurries. Winds light from the southeast. Alpine temperatures near -1 C and freezing levels 1500 m.
Saturday: Snow 5-10 cm at upper elevations. Wind light from the South. Alpine temperatures near -1 and freezing levels 1600 m.
Sunday: Snow 5-10 cm at upper elevations. Light wind from the South. Alpine temperatures -2 and freezing levels 1600 m.
Monday: Cloudy with some sunny periods and snow 5 cm. Light-moderate wind from the southwest. Alpine temperatures near -1 and freezing levels 1800 m.
Avalanche Summary
At treeline and in the alpine, the new snow combined with light to moderate wind may build fresh and reactive storm slabs. The new snow may have a poor bond to the old snow surfaces which are mostly crusts. Below treeline will see rain and will likely keep snow surfaces wet and weak below the treeline elevations. Loose wet avalanches are possible.
Cornices remain weak and fragile. They require a large berth from above and below as they are very unpredictable.
Over the past week natural and explosive triggered wet slab avalanches were reported mostly from large solar slopes and running to valley bottom up to size 3.5. An ongoing natural cycle of wet loose avalanches up to size 2 has been the theme with the warming.
Snowpack Summary
New snow will accumulate at treeline and in the alpine through the weekend building fresh and reactive storm slabs. Below treeline elevations will likely see rain. The new snow will be landing on a melt-freeze crust that extends to the alpine on solar slopes and 2100 m on polar slopes. It may bond poorly. Rain below treeline will likely keep the snow surfaces wet and weak.
Cornices are large and looming along ridgelines. They are weak and very unpredictable.
Terrain and Travel
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
- Keep in mind that wet avalanches can be destructive due to their high density.
Problems
Storm Slabs
New snow is forecast for upper elevations and the region may receive up to 30 cm by Sunday. Reactive storm slabs may exist if there is a poor bond to the old snow surfaces comprising of mostly crusts and firm snow on North facing alpine slopes.
Dry loose sluffing may be seen from steep terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Wet loose avalanches are possible below treeline with forecast rain. If a firm crust exists this problem is unlikely.
Aspects: All aspects.
Elevations: Below Treeline.
Likelihood
Expected Size
Cornices
Cornices are at their largest at this time of year. They are weak and unpredictable.
Aspects: North, North East, East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 26th, 2021 4:00PM
