Avalanche Forecast
Dec 19th, 2018–Dec 20th, 2018
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2:
Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3:
Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1:
Low
The avalanche danger rating below treeline will be low
Alpine
2:
Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2:
Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1:
Low
The avalanche danger rating below treeline will be low
Regions: Northwest Coastal.
As the storm tapers and the weather cools off, the snowpack will begin to gain some strength. Conservative terrain selection is still recommended, especially in the alpine and upper treeline areas.
Confidence
Low - Due to the number of field observations.
Weather Forecast
WEDNESDAY NIGHT: Cloudy with flurries, 5-10 cm, moderate southwest winds, alpine low temperature near -10°c. THURSDAY: A mix of sun and cloud with isolated flurries up to 5 cm, east to northeast winds, 20-40 km/h, gusting to 60 km/h, alpine high temperature near -5°c, low temperature near -10°c. FRIDAY: Cloudy with sunny periods and isolated flurries, southerly winds, 20-40 km/h, gusting to 55 km/h, alpine high temperature near -6°c, low temperature near -9°c. SATURDAY: Flurries, 5-10 cm, southeast winds, 20-40 km/h, gusting to 55 km/h, alpine high temperature near -4°c, low temperature near -8°c.
Avalanche Summary
Observations have been limited over the past week due to poor weather conditions, but with the enormous amount of snowfall there have likely been several cycles of natural avalanche activity. Several large natural avalanches (size 2-3) were reported in wind loaded alpine terrain near Stewart on Tuesday. A few smaller natural avalanches (size 1-2) were reported in steep terrain in the Shames area over the past few days.
Snowpack Summary
Over the past week an onslaught of storms has delivered 100-150cm of snow to the region. Warm temperatures have left the surface snow moist up to approximately 1000m, which will likely freeze into a crust with dropping temperatures this week. Strong wind has likely affected open terrain at higher elevations and formed thick wind deposits in lee terrain. All of this storm snow sits above an interface that was a concern during the start of the storm, but the strength of this layer has likely improved substantially over the past week. The interface is composed of surface hoar (feathery crystals), facets (sugary snow), and crusts that formed during the dry spell in early December. Deeper in the snowpack, there are several crusts, including an early season crust with facets near the bottom of the snowpack.
Avalanche Problems
Storm Slabs
Storm slabs have been building for the past week and could still be reactive to human triggering at upper elevations, especially on steep slopes in lee terrain.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.The new snow will require several days to settle and stabilize.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2.5