Avalanche Forecast

Archived

Jan 13th, 2022–Jan 14th, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

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, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

South Rockies.

The hazard will be most pronounced at upper elevations in the alpine, where sunshine and warm temperatures may destabilize the snowpack.

Confidence

Moderate - Uncertainty is due to rapidly fluctuating freezing levels. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Weather Forecast

Thursday night: Gradually increasing cloud. Freezing level falling to around 1200 m.

Friday: Cloudy up to around 2200 m elevation, which may be thick enough to give some very light precipitation. An above freezing layer of warm air will exist above around 2500 m. Winds light in the morning, increasing to moderate westerly in the afternoon.

Saturday: Snow flurries possible, otherwise cloudy. Moderate southwesterly winds. Treeline high around -2 °C, freezing level around 1500 m.

Sunday: Mostly dry with some clear spells. Moderate southwesterly winds. Freezing level around 1300 m.

Avalanche Summary

On Thursday, three very large avalanches were reported from this region. These avalanches failed on the early December crust and showed wide propagation. They occurred on southwest to southeast aspects and were naturally triggered in response to rising temperatures and solar radiation.

On Wednesday, one very large (size 3) and several smaller (size 1-2) wind slab avalanches were reported on mostly north to east aspects in the alpine. A large cornice fall (size 3) was also reported.

The broader area including the South Rockies and neighbouring regions has been experiencing a sporadic pattern of very large avalanches over the last couple of weeks.

Snowpack Summary

Recent new snow has settled fast and become dense due to warm temperatures. This snow sits on a variety of old surfaces, including soft snow in sheltered areas and wind slabs in exposed and open areas which formed over the past few days.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now typically down 80-150 cm. In the neighbouring Lizard-Flathead region, three very large avalanches were reported on this layer on Jan 13. This layer has created a tricky low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.

Terrain and Travel

Be aware of the potential for large avalanches due to the presence of a persistent slab.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Avoid freshly wind loaded terrain features.

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.

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.