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Avalanche Forecast

Archived

Mar 30th, 2021–Mar 31st, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Inland.

Storm slabs may be reactive to skier and rider triggering, especially in the Telkwa area where heavier snowfall amounts exist. They could be extra sensitive on wind-loaded slopes

The spring sun packs a punch and can quickly initiate natural avalanche activity and weaken cornices 

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Weather Forecast

Yet another Pacific frontal system hits the region Tuesday night bringing strong wind and new storm snow. Forecast snow amounts will vary across the region. 

Wednesday: Mix of sun and cloud with snow amounts 5-10 cm. Ridgetop wind strong from the South. Alpine temperatures near -6 and freezing levels 1000 m. 

Thursday: Mix of sun and cloud with light snow up to 10 cm. Ridgetop wind strong from the southwest and freezing levels 800 m.

Friday: Continued flurries 5-10 cm. Ridgetop wind strong from the southeast with freezing levels 1200 m. 

Avalanche Summary

On Monday, reports from the Telkwa area saw a widespread avalanche cycle that occurred over the weekend. This included loose dry avalanches at all elevations up to size 2 and wind slabs up to size 2.5. With the Telkwa receiving the most snow throughout the region this zone and the ranges to the West are likely a hot spot for avalanche activity in the upper snowpack and may take longer to stabilize and bond.

Avalanche size and sensitivity are expected to decrease over the next few days, however, reactive storm slabs are still anticipated, especially in wind-loaded slopes at upper elevations. If the sun comes out, it could quickly trigger natural avalanches within the new snow. 

Cornices are large at this time of year, and they become weaker when the sun hits them.

Snowpack Summary

15-35 cm of snow has fallen in the region over the weekend and another 20 cm fell in the Telkwa overnight. This was accompanied by strong southwest to northwest wind. Fresh wind slabs may exist on most slopes due to changing wind directions. At lower elevations, much of this precipitation fell as rain below treeline. The lower elevations are now showing a firm surface crust.

Buried 70-120 cm deep, a spotty layer of surface hoar may exist on sheltered north aspects, as well as a crust on south aspects and below 1450 m. Recent observations suggest that this interface is bonding.

The mid and lower snowpack is reported as well settled and strong in most areas. However, weak facets exist at the base of the snowpack in the more shallow snowpack zones within much of the region and have the potential to be triggered on steep, rocky slopes with a shallow or thin to thick snowpack; especially with large loads such as a cornice fall.

Terrain and Travel

  • Even brief periods of direct sun could produce natural avalanches.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded terrain features.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Caution around slopes that are exposed to cornices overhead.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.