Avalanche Forecast

Issued: Apr 11th, 2015 8:17AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

ghelgeson, Avalanche Canada

Cariboos.

While it feels like spring in the valley, the alpine has returned to winter. Stay on your toes as a potentially touchy wind slab likely exists at upper elevations.

Summary

Confidence

Fair

Weather Forecast

SUNDAY: Freezing level rising to 1500m. Moderate W/SW winds at treeline, strong W/SW winds at ridge-crest. Overcast skies, no significant precipitation expected.MONDAY: Freezing level rising to 1700m. Strong south winds at all elevations. Few clouds in the morning, quickly building to overcast by lunch. No significant precipitation expected during the day, 5 to 10cm of snow possible Monday night.TUESDAY: Freezing level constant around 1400m. Moderate NW/W winds at treeline, Strong W winds at ridge-crest. Broken cloud cover, no significant precipitation.

Avalanche Summary

No new activity to report from Friday. A few natural cornice failures were observed Wednesday & Thursday, but slabs were only triggered in steep, unsupported rocky features and even then had minimal propagation. On Tuesday cornice failure triggered a size 3 avalanche on a North facing feature at 2700m.

Snowpack Summary

The region picked up around 5 cm of snow Friday night accompanied by strong SW winds burying the old surface which consists of facets, surface hoar and crust. Prior to Friday nights storm the 15 to 30cm that fell the weekend of April 4th remained dry on high elevation polar aspects but had turned moist on east and west facing aspects. South facing features were moving into the spring corn cycle. Much of the snowpack has been reported as isothermal at mid and lower elevations.Two significant persistent weak layers composed of crust and facets exist in the snowpack. Although they appear to have gone dormant for the time being, we will continue to monitor them closely. Mid-March is down 40 to 80cm below the surface and Mid-February is down 80 to 200cm. Down at the bottom of the snowpack a weak layer of basal facets exists. Large loads like cornice/ice fall or even sustained warming could initiate an avalanche on this very deeply buried weak layer.

Problems

Wind Slabs

Snowfall Friday night was accompanied by strong SW winds, and these winds are expected to continue into Sunday. Fresh wind slabs are sitting on crust, facets and/or surface hoar which may keep them touchy into early next week.

Avoid freshly wind loaded features.>Wind slabs are likely most problematic immediately lee of ridge-crest. Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Ongoing winds are adding to the already large cornices that loom over many features, possibly increasing the likelihood of failure. A large cornice failure may be able to trigger a slab release on slopes below.

Extra caution needed on slopes that are exposed to cornices overhead.>Be aware of the potential for cornice fall to trigger surprisingly deep slabs.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Apr 12th, 2015 2:00PM