Avalanche Forecast

Issued: Mar 3rd, 2016 7:30AM

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

pmarshall, Avalanche Canada

South Columbia.

Storm slabs are highly reactive to human-triggering and conservative terrain selection remains critical for the next few days. Extra caution is required on south-facing slopes in the afternoon if the sun pokes out.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY: Cloudy with sunny breaks and light precipitation starting late in the day. Freezing levels reaching 1600 m late in the day with moderate to strong southwesterly ridgetop winds. SATURDAY: Periods of snow bringing another 5-15cm. Freezing levels steady around 2000-2200 m with strong southwesterly ridgetop winds. SUNDAY: Periods of snow. The freezing level is around 1600-1800 m and ridge winds ease to light and variable.

Avalanche Summary

Continued natural and rider-triggered avalanche activity up to size 2 was reported throughout the region on Wednesday. These slides occurred on all aspects, at all elevations, and were generally 30-60 cm deep. Reports from Tuesday include more of the same plus evidence of a widespread natural avalanche cycle that occurred early Monday, primarily in the Monashee Mountains, with avalanches up to Size 3 running on surface hoar buried late February.

Snowpack Summary

40-60 cm thick storm slabs are bonding poorly to on a crust on previously sun-exposed slopes and surface hoar on shady and sheltered slopes. Thicker and touchier wind slabs are lurking throughout exposed terrain at and above treeline. A weak layer of surface hoar and/or a sun crust buried February 21 is now close to a metre below the surface. Where it exists, this layer may become reactive to human triggers as the overlying slab develops. The surface hoar and/or crust layer buried February 10 is likely down over a metre. This layer was less reactive over the weekend with cooler temperatures, but remains a concern for large triggers like cornice falls or a smaller avalanches stepping down. Cornices are large and potentially weak and should be avoided where possible.

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.

Choose well supported terrain without convexities.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

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 metre.

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.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Cornices

Warm temperatures, strong winds, and possible sunny breaks are all factors that could weaken large droopy cornices.

Cornices become weak with daytime heating. >Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 4th, 2016 2:00PM