Avalanche Forecast

Archived

Mar 6th, 2019–Mar 7th, 2019

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.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Cariboos.

Convective snow showers may bring higher than forecast snowfall amounts to some areas. In areas that receive 20 cm or more, consider the danger rating to be MODERATE at all elevation bands.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Convective snow showers on Thursday could mean that some areas receive higher than forecast snowfall amounts.WEDNESDAY NIGHT - Mainly cloudy with flurries, up to 5 cm / southeast winds 10-20 km/h / alpine low temperature near -8THURSDAY - Mainly cloudy with flurries, 5 cm. / southwest winds 25-40 km/h / alpine high temperature near -8FRIDAY - Mainly cloudy with flurries, 3-5 cm / west winds 10-30 km/h / alpine high temperature near -10SATURDAY - A mix of sun and cloud / west winds, 15-30 km/h / alpine high temperature near -9

Avalanche Summary

No new avalanches have been reported in the region over the past few days, but observations in neighbouring regions have shown regular, generally small (size 1) wind slabs reacting to skier traffic at upper elevations. Avalanche activity on the mid January persistent weak layer has tapered off, however test results still suggest that this layer could be triggered by humans in specific locations. When persistent weak layers stop producing regular avalanches, they can become very difficult to manage. This weak layer has become a low likelihood/high consequence avalanche problem. Check out a recent MIN report from Allen Creek here that illustrates this.

Snowpack Summary

5-10 cm of snow is expected to fall overnight Wednesday and through Thursday. Some convective snow showers could mean that some areas see up to 20 cm.The new snow will sit mainly on wind slabs and facets (sugary snow) and a crust on sun exposed slopes. The wind slabs are also sitting on facets and they may continue to be reactive. At lower elevations, a weak layer buried in mid January can be found approximately 50-60 cm deep. This layer consists of surface hoar (feathery crystals) and facets, and may be combined with a crust on south facing slopes. This layer has been most reactive at treeline and below treeline. The lower snowpack is generally considered to be strong, except for shallow, rocky areas where cold temperatures continue to facet (weaken) the snowpack.

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.

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.