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Avalanche Forecast

Archived

Apr 3rd, 2021–Apr 4th, 2021

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

South Columbia.

Winter is still hanging on up there, with a fresh hit of snow arriving overnight and into Sunday. The new snow may be reactive in wind loaded features or where it sits over a crust. Check out our latest forecaster blog on managing these not-quite-yet-spring conditions.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Light precipitation spreading from north to south overnight Saturday into Sunday. Local enhancements of up to 20 cm may be found on southwest facing slopes in high elevation areas. Below the freezing level, precipitation will fall as light rain.

Saturday night: 5-10 cm new snow focused in the north of the region. Strong southwest wind. Alpine temperatures around -3. Freezing levels to 1500 m.

Sunday: 5-10 cm new snow focused in the south of the region. Light northwest wind. Alpine high temperatures around -6. Freezing level 1600 m.

Monday: Sunny. Light to moderate northwest wind. Alpine high temperatures around -2. Freezing level 2000 m.

Tuesday: Sunny with increasing cloud in the late afternoon. Light to moderate south wind. Alpine high temperatures around -1. Freezing level 2300 m.

Avalanche Summary

A couple of size 2 cornice failures were reported on Friday, one triggering a thin wind slab on the slope below. On Wednesday and Thursday, natural and skier triggered loose wet avalanches were reported on solar aspects size 1-2.5. 

Sporadic slab avalanches around size 2 have also been observed running on one or more of our recent curst layers. On Wednesday a larger (size 2), 45 cm-deep slab was triggered by a snowcat push in the Selkirks and is suspected to have failed on a surface hoar layer from late March.

Snowpack Summary

Surface crusts exist on solar aspects and below about 2000 metres. Above this elevation, 20-50 cm of recent snow in the Selkirk mountains and 10-20 in the Monashees has otherwise seen some redistribution by southwest to northwest wind, and seems to be bonding well with underlying surfaces.

At alpine and treeline elevations, a few layers of note are buried 50-100 cm deep including a layer of small surface hoar crystals on shady, wind-sheltered aspects and a series of crusts on solar aspects and below 1800 m. Overall the snow seems to be bonding well to these interfaces, although there have been a few isolated avalanches running on deeper crust layers in the past week.

Terrain and Travel

  • Closely monitor how the new snow is bonding to the crust.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Extra caution is needed around cornices under the current conditions.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.

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.