Avalanche Forecast

Issued: Mar 2nd, 2016 8:22AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. 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

High

Weather Forecast

THURSDAY: Periods of snow with a few centimeters of accumulation expected overnight Wednesday and throughout the day Thursday. Freezing levels reaching 1800m with light to moderate southwesterly ridgetop winds. FRIDAY: A mix of sun and cloud in the morning with light precipitation starting late in the day. Freezing levels reaching 2000m with light to moderate southwesterly ridgetop winds. SATURDAY: Cloudy with flurries bringing another 3-5cm. Freezing levels steady around 1800m and moderate to strong southwesterly ridgetop winds.

Avalanche Summary

Reports from Tuesday include a few explosives triggered storm slab avalanches up to Size 2 and isolated small skier triggered wind slabs and sluffs in steep terrain. 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

5-10cm of fresh snow adds to the 5-15 cm of recent storm snow bonding poorly to a melt-freeze crust on previously sun-exposed slopes and lower elevation terrain, and/or a layer of surface hoar on shady and sheltered slopes at treeline elevations. Thicker and touchier fresh wind slabs are 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.

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

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 a 60cm.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 3rd, 2016 2:00PM