Avalanche Forecast
Issued: Apr 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Cornices and Deep Persistent Slabs.
shorton,
Avalanche Canada
Danger will elevate throughout the day as slope warm up. Plan on finishing early and minimizing your exposure to avalanche terrain once it heats up. Read more in this Forecasters' Blog.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
A high pressure ridge brings clear skies and progressively warmer temperatures.
TUESDAY NIGHT: Clearing skies, light west wind, freezing level climbs from 1700 to 2000 m by the morning with treeline temperatures climbing to +2 C.
WEDNESDAY: Mostly sunny, light south wind, freezing level climbs from 2000 to 2700 m throughout the day, treeline temperatures climb to +5 C.
THURSDAY: Sunny, light south wind, freezing level steady around 2800 m, treeline temperatures around +8 C.
FRIDAY: Mostly sunny, light south wind, freezing level steady around 3000 m, treeline temperatures around +8 C.
Avalanche Summary
Warm sunny weather this week will cause wet loose avalanches and cornice falls. Natural slab avalanches will become an increasing concern after several days of warm weather.
On Sunday and Monday there were many small (size 1) wet loose avalanches on south-facing slopes at all elevations and a few size 2-2.5 cornice failures on north and east facing slopes. On Saturday there were a few naturally triggered wind slab avalanches (up to size 2) on northeasterly aspects in the alpine.
Snowpack Summary
Sunny skies and rising freezing levels will result in melting surfaces everywhere except north-facing alpine terrain. In the alpine 5-20 cm of snow is quickly settling and strengthening, although some wind slabs could linger on steep slopes. The recent snow has covered a variety of snow surfaces, including wind affected snow, crusts on solar aspects and at lower elevations, and soft snow on sheltered slopes at upper elevations.
The lower snowpack has been strong and settled over the past month, however the dramatic warming this week could potentially wake up weak basal facets. This is particularly a concern on steep, rocky slopes with a shallow or thin to thick snowpack.
Cornices are large, looming, and capable of triggering large avalanches when they fail.
Terrain and Travel
- Avoid exposure to sunny slopes, especially in the afternoon.
- Cornices become weak with daytime heating, travel early on exposed slopes.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- Watch for areas of hard wind slab on alpine features.
Problems
Loose Wet
Wet loose avalanches will start to run naturally on steep solar aspects when the sun comes out.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are large and looming along many ridgelines. They will become weak with daytime heating and could trigger avalanches on the slopes below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
Prolonged warming could increase the sensitivity of deeply buried layers in the snowpack. While these layers have not been reactive lately, you should practice increasing caution during this period of warm weather. Thin rocky slopes are most suspect.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 14th, 2021 4:00PM
