Avalanche Forecast

Issued: Mar 13th, 2017 4:22PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Persistent Slabs.

mgrist, Avalanche Canada

Cariboos.

Snow, strong wind and warming are a recipe for elevated danger. Conservative terrain use at all elevations is essential this week. Avoid overhead hazard!

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

We'll see warmer temperatures with strong winds and significant precipitation through the forecast period. TUESDAY: Snow (5-15cm) with STRONG southwest winds. Freezing levels near 1700m. WEDNESDAY: Another 15-25cm of fresh snow throughout the day accompanied by moderate south winds. Freezing levels remain at 1700m. THURSDAY: Flurries with another 5cm accompanied by moderate southwest winds. Freezing levels dropping to 1100m.

Avalanche Summary

A widespread natural avalanche cycle to Size 2.5 was reported below treeline on Monday afternoon as temperatures warmed up. On Friday morning, skiers were able to trigger a Size 1.5 storm slab (with good propagation) in a cross loaded slope near a shallow rocky area. Aspect was north/northeast. See here for their great MIN report.

Snowpack Summary

Warming temperatures on Monday afternoon destabilized the snowpack resulting in a widespread natural avalanche cycle below treeline. Use extra caution for the time being in what is normally a 'safer' elevation band. We've had 5-15cm of fresh snow (with moderate to strong southerly winds) each of the past four days. Touchy storm slabs can be found at all elevations with weaknesses within and under this recent snow. Recent moderate to strong southerly winds have created reactive wind slabs at treeline and above. All this recent snow is bonding slowly to faceted snow, thin sun crust on steep southerly aspects, as well as surface hoar in sheltered areas in some parts of the region.About 80-120 cm below the surface you'll likely find the mid-February persistent weakness, which is composed of a thick rain crust up to about 1700 m, sun crusts on steep solar aspects, and spotty surface hoar on shaded aspects. Professionals in the region have also warned that a 'threshold load' has been reached above this interface, particularly where it presents as a crust.Deep persistent weaknesses (over 1.5 metres down) still have the potential to react to human triggers or smaller slab avalanches.

Problems

Storm Slabs

Weaknesses within and below the recent storm snow are susceptible to human triggering. These storm slabs are particularly deep and touchy on slopes loaded by southerly winds and have the potential to step down to deeper persistent weaknesses.

If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Persistent weakness layered throughout the snowpack create the potential for very large step-down avalanches. The risk of triggering a deeper weak layer will be heightened while overlying storm slabs remain sensitive to human triggering.

Avoid or use extreme caution around thin snowpack areas.Avoid lingering in runout zones.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Mar 14th, 2017 2:00PM