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Avalanche Forecast

Archived

Mar 23rd, 2021–Mar 24th, 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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

New snow and wind forecast for Tuesday night through Wednesday morning will form fresh wind slabs at upper elevations.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

TUESDAY Night: Mainly cloudy with periods of snow, accumulation 5-15 cm, moderate west wind, treeline temperatures around -5 C, freezing level 800 m.

WEDNESDAY: Cloudy with flurries bringing 5-10 cm of new snow through the morning, moderate to strong southwest wind, treeline temperatures around -4 C, freezing level 1500 m.

THURSDAY: Mix of sun and cloud, light northwest wind, treeline temperatures around -3 C, freezing level 1600 m.

FRIDAY: Cloudy with sunny breaks, moderate northwest wind, treeline temperatures around -4 C, freezing level 1500 m.

Avalanche Summary

Reports on Monday showed several size 1.5-2 cornice releases with explosive control, as well as a few thin storm and wind slab avalanches to size 1.5 in the alpine. Loose wet and loose dry size 1 avalanches from steep terrain facing the sun were also reported in the afternoon.

Expect to see an increase in wind slab and possibly storm slab activity Wednesday with new snow and wind arriving Tuesday night.

Snowpack Summary

By Wednesday midday there may be anywhere from 10-20 cm of new snow from Tuesday night that has likely been redistributed by west and northwest winds. This adds to about 30+ cm accumulation from last 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

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Be alert to conditions that change throughout the day.
  • Be alert to conditions that change with elevation and sun exposure.
  • 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.