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Avalanche Forecast

Archived

Mar 23rd, 2022–Mar 24th, 2022

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

Regions

Northwest Inland.

Caution around cornices and wind slabs at elevations with dry snow.

Confidence

Moderate - Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region.

Weather Forecast

Wednesday night: A trace of snow. Moderate southwest wind. Alpine low around -8 °C. Freezing level dropping to valley bottom. 

Thursday: A mix of sun and cloud. Moderate southeast wind. Alpine high around -6 °C. Freezing level 1100 m.

Friday: Cloudy with sunny periods. Light south wind. Alpine high around -5 °C. Freezing level 1100 m.

Saturday: Mostly cloudy. Moderate southeast wind. Alpine high around -5 °C. Freezing level 1100 m.

Avalanche Summary

Reports from Tuesday and Wednesday indicate limited avalanche activity during the rain event. A few loose wet avalanches were reported up to size 1.5 at 1800 m and lower. Over the last three days size 1.5-3 avalanches have resulted from natural cornice failures triggering wind slabs on slopes below.

Persistent slab avalanches on a weak layer of surface hoar crystals buried in late February surprised a few people last week with accidental and remote triggers. The layer was most active on north-northeast aspects between 1200 and 1600 m in areas north of Hazelton. This problem has likely become more difficult to trigger as a bridging crust forms over wet surface snow.

Snowpack Summary

Wet snow or crusty conditions can be found at least as high as 1700 m. Wind slabs may be found at high elevations that have remained dry.

A couple of layers of weak crystals in the upper snowpack appear to be bonding. Our field team's latest snowpack tests produced no results at these interfaces. Additionally, we suspect that the surface crust will help bridge these layers, further decreasing their likelihood of triggering.

A thick crust formed in mid-February is now buried 50-80 cm deep. It is unlikely to present an avalanche problem under the current conditions and in fact bridges any underlying instabilities in the lower snowpack.

Terrain and Travel

  • A crust on the surface will help bind the snow together, but may make for tough travel conditions.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.