Avalanche Forecast

Issued: Apr 9th, 2015 8:34AM

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.

Watch for clues of changing conditions as there is potential for fresh wind slab formation on alpine features Friday.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

FRIDAY: Freezing level holding at 1800m. Strong south winds at treeline, strong to extreme SW winds at ridge-top. Clear skies at dawn building to overcast by lunch. No significant precipitation expected during the day. 2 to 5mm of precipitation expected Friday night, less than 10cm total snowfall expected.SATURDAY: Freezing level hovering around 1500m. Scattered flurries, less than 5cm of snow expected. Moderate W/SW winds at treeline, strong W winds at ridge-top. Overcast.SUNDAY: Freezing level rising to 1500m. Moderate W winds at treeline, strong W/SW winds at ridge-top. Overcast skies, no significant precipitation expected.

Avalanche Summary

A few natural cornice failures were observed Wednesday, 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 current surface consists of surface facets and surface hoar. Below this is the 15-30cm of new snow that fell last weekend. This snow remains dry on high elevation polar aspects but has turned moist on east and west facing aspects. South facing features are moving into the spring corn cycle. Moist snow exists underneath this most recent storm snow in most of the region.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

After a few days of very little air movement, strong S/SW winds are expected to ramp up Friday morning. While there isn't a lot of snow available for transport, I expect that wind slabs will be most problematic immediately lee of ridge-crest.

Be cautious as you transition into wind affected terrain.>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

Expected Size

1 - 3

Cornices

Increased winds Friday should add 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.

When traveling in the alpine, be SURE you're on the ridge, and not on a cornice.>Extra caution needed on slopes that are exposed to cornices overhead.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Apr 10th, 2015 2:00PM