Avalanche Forecast

Issued: Mar 1st, 2016 8:36AM

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

ccampbell, Avalanche Canada

Purcells.

Touchy and growing storm slabs will keep avalanche danger elevated this week. Riding should be great, but a conservative approach is recommended. Stick to simple terrain.

Summary

Confidence

Moderate - Wind speed and direction is uncertain on Thursday

Weather Forecast

WEDNESDAY: After 10-15cm overnight, aÂ relatively dry day is expected with another few cm of accumulation before tapering off late in the day. Freezing levels are expected to reach 1600m with light southwesterly ridgetop winds. THURSDAY: Periods of snow with 3-5cm of accumulation expected throughout the day. Freezing levels reaching 1800m with light to moderate southwesterly ridgetop winds. FRIDAY: Another 3-5cm of accumulation expected throughout the day. Freezing levels reaching 2000m with light to moderate southwesterly ridgetop winds.

Avalanche Summary

Reports from Monday several natural and human triggered relatively harmless wind slab and dry loose snow avalanches. Wind and storm slabs should increase in size and likelihood throughout the week with continued light snow and moderate ridge winds. Late last week there were a couple reports of failing cornices triggering persistent slabs up to 60 cm deep on slopes below.

Snowpack Summary

5-15 cm of new snow overlies a melt-freeze crust on previously sun-exposed slopes and lower elevation terrain, and might be covering a layer of surface hoar on shady and sheltered slopes at treeline and in the alpine. Fresh wind slabs are likely lurking in exposed lee and cross-loaded terrain. The surface hoar and/or crust layer buried in mid-February is now down 40-70cm. This layer was less reactive over the weekend with cooler temperatures. Large weak cornices remain concerning and have recently triggered persistent slabs on slopes below. The early January surface hoar/facet layer is typically down 70-120cm. Triggering an avalanche on this layer has become unlikely but it still has isolated potential to produce very large avalanches with a heavy trigger. In general, the lower snowpack is well settled and strong, apart from some thin snowpack areas where basal facets exist.

Problems

Storm Slabs

Fresh storm slabs are primed for human triggering. Particularly touchy wind slabs are lurking below ridge crests, behind terrain features and in cross loaded gullies.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Heavier triggers such as cornice falls, groups of people, or smaller avalanches stepping down, or lighter triggers (such as a person) in the wrong spot may be enough load to trigger a crust and/or surface hoar layer down around 60cm.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 2nd, 2016 2:00PM