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Avalanche Forecast

Archived

Mar 24th, 2021–Mar 25th, 2021

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.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Wind slabs may linger in steep terrain on all aspects at higher elevations. Best to avoid sun-exposed slopes during the heat of the day if the skies are clear.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Clearing, light northwest wind, treeline temperatures around -5 C, freezing level 1200 m.

THURSDAY: Clear skies, light northeast wind, treeline temperatures around -3 C, freezing level 1600 m.

FRIDAY: Mostly cloudy, light southwest wind, treeline temperatures around -4 C, freezing level 1400 m.

SATURDAY: Mostly cloudy with afternoon snowfall, accumulation 1 to 3 cm, moderate southwest wind, treeline temperature around -3 C, freezing level 1500 m.

Avalanche Summary

A few cornices were triggered naturally and from explosives on Tuesday and Wednesday. They were very large, as is expected at this time of year.

Looking forward, wind slabs and cornices may remain triggerable at higher elevations and use caution on sun-exposed slopes if clear skies prevail.

Snowpack Summary

Around 5 to 10 cm of snow accumulated Tuesday night, with strong wind from the southwest switching to northeast. New wind slabs likely formed during this time, which may linger in steep, alpine terrain features. This snow adds to the 30+ cm that accumulated on the weekend. All of the new snow sits above a widespread crust, with the exception of high north-facing terrain. Observations suggest the snow has bonded well to these old interfaces. There are currently no concerning weak layers in the snowpack, although a spotty early season facet layer deep in the snowpack could return as a problem later in the season.

Remember that cornices along ridgelines are large at this time of year and always have the possibility of failing naturally or from the weight of a human.

Terrain and Travel

  • Carefully evaluate steep lines for wind slabs.
  • Minimize exposure to sun-exposed slopes 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.