Avalanche Forecast

Archived

Mar 5th, 2022–Mar 6th, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

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.

A weak crust/facet layer remains a concern, especially in the north of the region. The layer is expected to be most reactive on shaded aspects around 1600-2000 m. Check out the recent forecaster blog for more details.

Confidence

Low - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

A ridge of high pressure brings one more day of dry and sunny conditions for Sunday before conditions change on Monday.

Saturday Night: Mainly clear, light to moderate N wind, freezing levels 600-1200 m.

Sunday: Mainly sunny, light to moderate N wind, freezing levels climbing to around 2000 m.

Monday: Mainly cloudy with flurries in the afternoon, light to moderate NW wind, freezing levels reaching around 1500 m in the afternoon.

Monday night and Tuesday: Snowfall up to 10 cm, light to moderate NW wind, freezing levels around 800 m.

Avalanche Summary

On Friday, numerous loose avalanches were observed on steep sun-exposed slopes. No new slab avalanches were reported.

On Thursday, some natural wet slabs up to size 1.5 were reported in the north of the region as well as several natural wind slabs. Natural loose avalanches were also observed on steep sun-exposed slopes. In the Coquihalla, a few glide slab avalanches were observed.

This MIN report from the north of the region on Thursday describes whumpfing and shooting cracks which suggests persistent weak layer buried late-February is reactive in this part of the region.

In the neighbouring Sea to Sky region, numerous natural and human-triggered persistent avalanches have been observed between Wednesday and Friday which failed on the February crust/facet interface. The snowpack structure is expected to be similar in the north of the Inland region and the persistent slab problem should be expected until proven otherwise.

Snowpack Summary

A surface melt-freeze crust is now expected on all aspects below around 1500 m and on sun-exposed slopes into the alpine. Dry surface snow is still expected on shaded aspects at treeline and in the alpine, and recent periods of moderate northerly wind may be redistributing this old storm snow and forming wind slabs in exposed high elevation terrain.

Two weak interfaces from February are typically down 40-60 cm in the north of the region and as deep as 80 cm in the Coquihalla. In the north of the region, these layers are expected to be very close together and may be acting as a single weak layer like the neighbouring Sea to Sky. In the south of the region, there may be 30-40 cm of snow between the layers which may have resulted in the layers being less reactive compared to the north. While the layers have not produced the same widespread avalanche activity compared to the neighbouring Sea to Sky region, a persistent slab problem still remains a major concern, especially in the north of the region where the snowpack structure is expected to be quite similar. In the Sea to Sky, the interface has been most reactive on shaded aspects between 1600 and 2000 m. There were also some avalanches on southerly aspects earlier in the week but with each subsequent day of melt-freeze conditions, the persistent problem is becoming less likely on sun-exposed slopes.

Terrain and Travel

Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Problems

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.

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.

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.