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Avalanche Forecast

Archived

Apr 18th, 2022–Apr 19th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Steady, light snowfall and bouts of elevated wind may be just enough to form new wind slabs to manage on Tuesday, particularly in coastal areas. Monitor new snow amounts and reactivity as you gain elevation.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

MONDAY NIGHT: Cloudy with continuing flurries bringing about 5 cm of new snow. Moderate east or northeast winds.

TUESDAY: Cloudy with continuing flurries bringin new snow totals to 10-20 cm, continuing overnight. Light east winds becoming strong south in the afternoon. Treeline high temperatures around -3.

WEDNESDAY: Clearing with another 5cm of new snow from the overnight period. Light to moderate east winds. Treeline high temperatures around 0.

THURSDAY: Mainly cloudy. Light east winds shifting southwest. Treeline high temperatures around 0.

Avalanche Summary

Sunday's reports included one observation of a large (size 2.5) natural cornice fall northwest of Terrace, a great reminder of continuously looming cornice hazards. Late in the afternoon, wet loose releases reaching size 2.5 (large) were observed on steep south aspects in the Icy Pass area. 

Saturday's reports included observations of an older natural size 3 (very large) wind slab as well as pinwheeling and minor point releases from steep solar terrain.

On Thursday, a vary large (size 3.5) natural cornice failure triggered a deep slab on the steep slope below which ran full path.

Numerous natural wind slabs (size 1.5-3) were observed in the alpine on Monday through Wednesday last week as a result of northeasterly outflow winds.

Snowpack Summary

10-20 cm of new snow (focused south and west) is expected to accumulate by end of day Tuesday, mainly burying heavily wind-affected surfaces in open areas, the product of strong outflow wind early last week. Some sheltered areas may still hold soft snow that our flurries will add to. The new snow will likely bury melt-freeze crust on solar aspects.

Below 1200 m, a widespread crust exists on the surface. Above 1200 m, 40 to 80 cm of settled storm snow rests on a hard melt-freeze crust from late March. The snow has been bonding to this crust.

Terrain and Travel

  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs are most reactive during their formation.

Problems

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.

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.