Avalanche Forecast

Issued: Mar 13th, 2017 4:07PM

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

cgarritty, Avalanche Canada

South Coast.

Tuesday's danger hinges on the snow line. Rain is expected all the way to treeline, so you'll need to increase the rating by one step if you encounter more than 20 cm of new snow at treeline.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Tuesday: Periods of rain and wet snow bringing around 60mm to lower elevations and 50-60 cm of new snow to high alpine elevations. Strong southwest winds. Freezing level to 1700 metres with alpine temperatures around 0 to -1. Wednesday: 15mm of rain below about 800 metres, with around 15 cm of new snow above. Moderate southwest winds. Freezing level to 1200 metres with alpine temperatures of -1. Thursday: Flurries bringing 10 cm of new snow. Moderate southwest winds. Freezing level to 900 metres with alpine temperatures of around -2.

Avalanche Summary

No new avalanches have been reported, but it should be noted that the warm, stormy weather has been discouraging some backcountry travel and obscuring visibility into alpine terrain.Looking forward, the primary hazard will exist where new snow is accumulating instead of rain. This will become increasingly relevant as you reach upper treeline elevations or if you are exposed to alpine slopes overhead. As rain continues to fall, ongoing potential also exists for loose wet avalanche activity, especially on steeper slopes. Ongoing rain and snow at higher elevations will also maintain the risk of large avalanches releasing over the late February interface. Large, open terrain features and avalanche paths should be avoided while this potential exists.

Snowpack Summary

Heavy rain has saturated the upper snowpack at all but high alpine elevations after roughly 50mm of precipitation fell over Sunday night and Monday morning. Any new snow that may have accumulated at high alpine elevations is likely to remain reactive to human triggering over the short term. At higher elevations, lingering potential may exist for loading from rain or snow to promote reactivity at the late February interface, roughly 1.5 metres deep. This layer is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. An avalanche on this layer would be large and very destructive. No concerns exist below this interface and the snowpack at treeline and below is generally well settled and strong.

Problems

Storm Slabs

Up to 60 cm of new snow over Monday night and Tuesday will form thick storm slabs on the surface in the alpine. These slabs will be primed for human triggering. Expect stability to deteriorate as you gain elevation and as snow continues to fall.

Be alert to overhead hazards and to danger increasing with elevation.Use extra caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Very Likely

Expected Size

1 - 2

Loose Wet

A natural loose wet avalanche cycle has already occurred, but up to 60 mm of rain in the forecast will sustain the potential for further loose wet avalanche activity at lower elevations on Tuesday.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.Be cautious of sluffing in steep terrain.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Storm snow from the past week sits over a buried persistent weak layer. Thick storm slabs in the alpine may have enough mass to step down to this layer while sustained rainfall may be enough to reawaken it at lower elevations.

Avoid traveling in large avalanche paths at all elevations.Be aware of the potential for very large avalanches due to deeply buried weak layers.Be alert to more dangerous conditions at alpine elevations.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

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