Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Apr 19th, 2021–Apr 21st, 2021

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

Regions

North Rockies.

Wet loose avalanches become increasingly likely during the heat of the day. Back off slopes as the surface becomes moist or wet with daytime warming and avoid slopes with large cornices overhead. 

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

  

MONDAY NIGHT: Clear / Light, north ridgetop wind / alpine low temperature -6 / Freezing level 1000 m.

TUESDAY: Sunny / Light, northwest ridgetop wind / alpine high temperature 8 / Freezing level 2400 m.

WEDNESDAY: Mostly sunny / Moderate, northwest ridgetop wind / alpine high temperature 6 / Freezing level 2000 m.

THURSDAY: Mostly sunny / Light, north ridgetop wind / alpine high temperature -2 / Freezing level 1100 m.

Avalanche Summary

A size 3 naturally triggered wet slab avalanche was reported on a southwest aspect in the alpine near McBride on Monday.

Numerous explosive triggered wet slab avalanches size 3-3.5 and one size 3.5 deep persistent slab avalanche were reported on solar aspects on Friday.

There have been some large deep persistent slab avalanches triggered by warming to the south around Jasper and Banff, and we suspect this problem may extend into the North Rockies.

Sustained warming can increase the likelihood of large avalanches failing on deeply buried weak layers.This is most likely to occur on steep, rocky alpine slopes with a shallow or thin to thick snowpack. 

Snowpack Summary

Successive days of very high freezing levels created moist surfaces at all elevations/aspects. Clear skies and cooling temperatures have formed firm crusts overnight which will lock up the snowpack until the surface crust melts. Avalanche danger can increase rapidly after the sun melts the frozen snow surface and begins to penetrate deeper into the snowpack. Strong solar radiation and warming often trigger wet loose avalanches and large cornice failures. Cornice falls could trigger large avalanches on deeply buried weak layers. 

Strong solar radiation and warm temperatures have the potential to reactivate deeply buried weak layers such as weak facets at the bottom of the snowpack. The most likely areas to be concerned about deeper weak layers are shallow parts of the region along the eastern slopes of the Rockies like Core Lodge, Wolverine, Bullmoose, Upper Burnt and perhaps around Mt. Robson. In general, steep, rocky slopes with a shallow or thin to thick snowpack are most suspect and should be avoided.

Terrain and Travel

  • Avoid travelling on slopes below cornices.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Avoid exposure to sunny slopes, especially in the afternoon.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.