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Avalanche Forecast

Archived

Apr 20th, 2021–Apr 21st, 2021

Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.
Alpine
Below Threshold.
Treeline
Below Threshold.
Below Treeline
Below Threshold.

Regions

Little Yoho.

Good travel conditions exist right now with dry snow on high north aspects. Start and finish your trips early to take advantage of lower avalanche danger in the mornings

Weather Forecast

Wednesday looks like another beautiful day to be in the mountains. Clear skies, a good freeze and slightly warmer than Tuesday. Winds are forecast to increase to moderate from the NW throughout the day and bring some clouds by afternoon. Thursday and Friday are looking to be cool with light snow and light winds.

Snowpack Summary

Dry snow exists above 2200 m on north aspects, but has been cooked by the sun on solar aspects where multiple crusts exist in the snowpack. Persistent layers in the mid and lower snowpack were re-activated in a few instances during the heating last week producing large avalanches with large loads (cornice failures and explosives).

Avalanche Summary

Some loose wet activity was observed as the day warmed up, but overall, much less than during last weeks warmup.

Confidence

Problems

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.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.