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Avalanche Forecast

Archived

Apr 28th, 2023–Apr 29th, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Northwest Coastal, Northwest Inland, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson, Kispiox, Microwave-Sinclair, Ningunsaw, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

A high freezing level will destabilize the snowpack, potentially triggering numerous different avalanche problems. Check out the latest Forecasters' Blog for more information.

Confidence

Moderate

Avalanche Summary

Riders should expect wet loose or slab avalanches and cornice failures during periods of warm air, with associated sunny skies or rain. Avoiding steep slopes when the snow feels sloppy and avoiding cornice exposure are good travel habits.

The likelihood of triggering very large avalanches releasing on the buried weak layers described in the Snowpack Summary will increase with each day of warming with this spring weather. This is particularly true for days without an overnight surface refreeze. Humans are most likely to trigger these layer in steep and rocky slopes where the snowpack is relatively thin.

Snowpack Summary

A moist snow surface is expected with a high freezing level, which may or may not freeze into a melt-freeze crust overnight.

Various layers of surface hoar, facets, and crusts may be found around 50 to 150 cm deep in coastal areas and 30 to 50 cm in shallower snowpack areas in the north and east of the region.

Weak faceted grains may exist near the base of the snowpack, particularly in shallower snowpack areas.

Cornices are large and looming at this time of year and will weaken with daytime warming.

Weather Summary

The freezing level will peak at 3300 m Friday night before slowly declining to 2500 m for Saturday with associated sunny skies. Sunday will see light rain or high alpine snow with a freezing level around 2200 m. A mix of sun and cloud with a rising freezing level to 2500 m is expected for Monday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Cornice failures could trigger very large and destructive avalanches.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.