Avalanche forecast

Northwest Inland

Feb 18 – 19, 2020Avalanche Canada
View on map
Archived · expired 7 years ago

Avalanche danger

Thu
Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
Open full map

Highlights

Avalanche danger may have improved but buried weak layers make for a tricky snowpack situation. Conservative terrain choices are recommended with caution around wind loaded features, steep rollovers in open trees and steep sun exposed slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    10-40 cm of snow from the past week has seen redistribution at alpine and treeline elevations, with wind slabs forming in lee features. With winds easing Tuesday, natural activity will likely slow down but the potential for human triggering of wind loaded pockets may persist.

    Steep sheltered slopes at lower elevations remain capable of producing storm slab releases with a trigger, particularly in parts of the region with 30 or more cm of recent snow.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2.5–3.5

    During the first half of the month there were many very large and destructive avalanches failing on deeply buried weak layers near the bottom of the snowpack. The bulk of this activity occurred above treeline on north through east facing aspects, but any large alpine slopes that have not yet avalanched should be treated as suspect. Wind slab or cornice releases are likely triggers for this problem. Human triggering is most likely in shallow, rocky areas where the snowpack transitions from thick to thin.

Confidence

Moderate -

Weather Forecast

Monday night: Mainly cloudy. Light northwest wind. Alpine low -10 C. Freezing level valley bottom.

Tuesday: Mix of sun and cloud. Light northwest to southwest winds. Freezing level 700 m.

Wednesday: Mix of sun and cloud. Moderate southwest winds, building to strong at ridgetop. Freezing level 400 m.

Thursday: Increasing cloud. Strong southwest winds, approaching extreme at ridgetop. Freezing level 400 m.

Avalanche Summary

Reports from the weekend consisted of several human triggered storm slabs size 1-1.5 at treeline and below, as well as a few natural (possibly cornice-triggered) slabs up to size 2.5 on north to east aspects in steep open bowls at treeline. Reports from Friday included an observation of a large cornice-triggered wind slab in Morning Bowl - see the report here. 

During the first half of the month there were many very large and destructive avalanches failing on deeply buried weak layers near the bottom of the snowpack. The bulk of this activity occurred above treeline on north through east facing aspects, but any large alpine slopes that have not yet avalanched should be treated as suspect. A few examples of MIN reports of large events February 8-11 include Hudson Bay, Kathlyn Face, French Peak, Pine Creek Trail, and Babines.

Snowpack Summary

10-40 cm of snow from the past week has seen some redistribution at alpine and treeline elevations, with wind slabs forming in lee features. At treeline and below, it may sit over patches of surface hoar in wind sheltered areas or crusts on solar aspects and below 1200 m.

A weak layer of facets that formed during the January cold snap is now about 60-120 cm below the surface while an early season crust lurks at the base of the snowpack. A few large avalanches were triggered on these layers in the first half of the month.

Terrain and Travel

  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Regions covered