Avalanche Forecast

Archived

Apr 16th, 2023–Apr 17th, 2023

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, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Heightened avalanche conditions exist on wind-affected slopes where there could be deep deposits of new snow.

Confidence

Moderate

Avalanche Summary

No new avalanches were reported over the weekend (at the time of publishing), however, some wind slab avalanches may have occurred during the peak of the storm on Sunday.

Last week, several remotely triggered storm and wind slab avalanches were reported. They typically occurred between 2000 and 2300 m and on a variety of aspects. A layer of facets and/or a crust down around 60 cm is likely responsible. Check out this MIN report for an example of these avalanches.

Snowpack Summary

The recent storm only delivered 5 to 15 cm of snow to this region, but strong southerly wind would have formed deeper and potentially reactive wind slabs on lee terrain features. This snow overlies a crust at treeline and below. In the alpine, this snow sits over a variety of layers including dry snow and wind slabs on north aspects and sun crusts and wind-pressed snow on south aspects.

A layer of facets and a crust from early April can be found down up to 60 cm at treeline and above.

The base of the snowpack remains faceted and weak. Avalanche activity has not been observed on this layer recently, but concern remains for shallow rocky snowpack areas.

Weather Summary

Sunday night

Scattered flurries with 5 cm of snow, 30 to 40 km/h southwest wind, treeline temperatures drop to -12 °C.

Monday

Clear periods in the morning, then increasing cloud in the afternoon, no significant precipitation, 20 km/h south wind, treeline temperatures warm to -6 °C.

Tuesday

2 to 4 cm of new snow overnight then mix of sun and cloud during the day, 20 km/h southwest wind, treeline temperatures around -5 °C.

Wednesday

Mix of sun and cloud, isolated flurries with trace amounts of snow, 20 km/h south wind, treeline temperatures around -4 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be carefull around freshly wind loaded features.
Use ridges or ribs to avoid areas of wind loaded snow.
Remote triggering is a concern, watch out for adjacent and overhead slopes.
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.