Avalanche Forecast

Issued: Mar 12th, 2017 4:39PM

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.

A warm storm will bring rain, snow, and a range of avalanche hazards on Monday. Be aware of hazards changing and increasing as you gain elevation.

Summary

Confidence

Moderate - Freezing levels are uncertain

Weather Forecast

Sunday night: Periods of snow bringing 20 cm of new snow to higher elevations. Rain below about 1000 metres. Moderate to strong southwest winds. Monday: Continuing snowfall with 30 cm accumulating at higher elevations. Rain below about 1300 metres. Moderate southwest winds. Freezing level rising to 1700 metres by afternoon. Alpine temperatures around 0. Tuesday: Flurries bringing 5 cm of new snow to alpine elevations and intensifying overnight. Rain below about 1400 metres. Light to moderate south winds increasing over the day. Freezing level to 1800 metres and rising overnight. Alpine temperatures around 0 to +1. Wednesday: Continuing flurries bringing up to 10 cm of new snow. Moderate to strong southwest wind. Freezing level dropping from 2000 metres to 700 metres over the day. Alpine temperatures around 0 to -1.

Avalanche Summary

No new avalanches have been reported, but it should be noted that stormy weather has been discouraging some backcountry travel and obscuring visibility into alpine terrain.Looking forward, expect a change in avalanche hazards as you transition to higher elevations. Thick, reactive storm slabs can be expected at higher elevations, which increases the need for awareness of overhead hazards. Heavy rain will increase danger from loose wet avalanches at lower elevations. Large persistent slab avalanches may also remain sensitive to human triggering or to smaller avalanches in isolated areas of the alpine.

Snowpack Summary

Up to 50 cm of new snow can be expected to accumulate into touchy storm slabs on the surface at higher elevations by Monday afternoon. Below the surface, last week's stormy weather brought 130-200 cm of recent snow to the South Coast mountains. Below all the recent storm snow, you'll find the late-February interface. This layer is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. Our supportive surface crust is likely to prevent triggering this layer at treeline and below, but this interface may remain reactive at alpine elevations. Although triggering this layer may be unlikely, doing so would produce a very large and destructive avalanche. Substantial snowfall and warming in the forecast are two factors that may promote reactivity at this interface on Monday. Below this interface, the mid and lower snowpack appear to be well settled and strong.

Problems

Storm Slabs

Another pulse of snow and wind over Sunday night and Monday will leave fresh storm slabs on the surface at higher elevations. Expect stability to deteriorate as you gain elevation and as snow continues to fall.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2

Loose Wet

A natural loose wet avalanche cycle has already occurred, but up to 50 mm of rain in the forecast will reawaken the potential for further loose wet avalanche activity at lower elevations on Monday.

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

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 and very large avalanches may still be possible in isolated alpine terrain. A supportive crust is likely to prevent human triggering this layer at lower elevations.

Be alert to more dangerous conditions at alpine elevations.Be aware of the potential for very large avalanches due to deeply buried weak layers.If triggered, storm slabs may step down to deeper layers resulting in very large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Mar 13th, 2017 2:00PM