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Avalanche Forecast

Archived

Apr 10th, 2021–Apr 11th, 2021

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

Regions

North Columbia.

Wind slabs may remain sensitive to triggering Sunday. The sun can pack a punch at this time of year and the new snow will be particularly sensitive to it. Be ready to back off sunny slopes before the snow surface is moist or wet.

Confidence

High -

Weather Forecast

A ridge of high pressure sets up over the province. Freezing levels are forecast to steadily rise through the week.

Saturday night: Clearing. Wind easing to light northwest. Alpine temperature around -12. Freezing level valley bottom.

Sunday: Mix of sun and cloud. Light northwest wind. Alpine temperature around -8. Freezing level 1300 m.

Monday: Sunny. Light to moderate northeast wind. Alpine temperature around -6. Freezing level 1500 m.

Tuesday: Sunny. Light to moderate northeast wind. Alpine temperature around -4. Freezing level 1800 m.

Avalanche Summary

Wind slabs have shown quite limited reactivity in the last couple of days, a few natural and ski cut size 1-1.5 were observed on Saturday. On Friday, most activity in the recent snow has been limited to size 1 loose snow avalanches. One size 2 was reported.

A couple of natural cornice failures size 2.5 observed Thursday did not trigger slabs on slopes below.

Neighboring Glacier National Park reported a few very large (size 3-4) glide slab releases on Thursday. Glide slabs are hard to predict and can release at any time so it is important to avoid slopes with glide cracks.

Snowpack Summary

20-30 cm of recent snow may have formed pockets of wind slab on leeward slopes and behind terrain features. On North aspects in the alpine, the recent snow sits on dry wintery snow surfaces and possibly surface hoar on wind-sheltered slopes. Elsewhere, it sits on a series of melt-freeze crusts on all aspects below 1900 m and southerly aspects to mountain top. Reports indicate snow is bonding well at these interfaces.

The recent warm weather is expected to have helped old persistent weak layers heal, including a few crusts buried over the last month as well as a facet layer 150 cm deep from the mid-February cold snap.

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.