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Avalanche Forecast

Archived

Apr 3rd, 2021–Apr 4th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia.

Winter is still hanging on up there, with a fresh hit of snow arriving overnight. 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

Highest snowfall amounts will be on southwestern facing slopes in the Monashees and northern Selkirks. Below the freezing level, precipitation will fall as rain.

Saturday night: 10-20 cm new snow. Moderate to strong southwest winds. Alpine temperatures around -5. Freezing level 1500 m.

Sunday: Continued flurries bringing up to 5 cm. Light northwest wind. Alpine high temperatures around -6. Freezing level 1500 m.

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

Tuesday: Sunny with increasing cloud in the late afternoon. Wind increasing to moderate to strong southwest. Alpine high temperatures around -1. Freezing level 2200 m.

Avalanche Summary

No reports of avalanche activity since Wednesday when small (size 1) natural and skier triggered loose wet avalanches were observed on south aspects, running on a recent crust layer. One recent natural size 2 cornice failure was also noted.

On Tuesday, a skier triggered size 2.5 involvement was reported in neighboring Glacier National Park resulted in lost gear and minor injuries. The avalanche is suspected to have run on a buried crust in the upper snowpack.

Snowpack Summary

5-20 cm of new snow arrives overnight with moderate to strong southwest wind. This has likely added to wind affected surfaces and cornices in the alpine and to settled dry snow on sheltered, shaded aspects above about 1900 m. Below this elevation and on solar aspects the new snow dusts crusty surfaces down to 1500 m. Below this elevation, the moist snowpack is quickly diminishing.

At alpine and treeline elevations, a widespread crust exists (except on north-facing slopes above 1800 m) buried 50-100 cm deep. Overall the snow seems to be bonding well at this interface, although there have been a few isolated avalanches running on deeper crust layers over the past few weeks.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • 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.