Avalanche Forecast

Issued: Apr 10th, 2015 10:26AM

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

ghelgeson, Avalanche Canada

South Columbia.

If alpine storm snow totals are less than 10cm, the alpine danger rating will likely be Moderate.

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY NIGHT: 2 to 5mm of precipitation is possible, less than 10cm of total snow expected. Extreme SW winds.SATURDAY: Freezing level hovering around 1500m. 2 to 6mm precipitation resulting in 2 to 10cm of snow. Moderate SW winds at treeline, moderate to strong SW/W winds at ridge-top.SUNDAY: Freezing level starting at 1000m, rising to 1500m. Light W/SW winds treeline, Moderate W winds at ridge-top. Overcast. No significant precipitation expected.MONDAY: Freezing level hovering around 1500m. Light variable winds at treeline. Moderate SW winds at ridge-top. Overcast. No significant precipitation expected.

Avalanche Summary

In two separate incidents Thursday cornice fall triggered deep persistent slabs when it impacted slopes below. Both incidents were on north facing alpine features. Loose wet avalanches to size 2 were also observed from south through west facing terrain.

Snowpack Summary

The current surface consists of surface facets and surface hoar. Below this is the 10 to 45cm of snow that fell last weekend. This snow remains dry on high elevation polar aspects but has turned moist on east and west facing aspects and south facing features are moving into the spring corn cycle. Just below this snow you'll the supportive late-March crust that is thought to exist up to around 2100m. Moist snow underneath the late-March crust is ubiquitous 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 140cm. Observations indicate that there is significant faceting occurring between the two crusts. While an avalanche failing at either of these interfaces is unlikely, it may still be possible on steep unsupported alpine features.

Problems

Wind Slabs

A relatively small amount of snow Friday night and Saturday accompanied by strong SW winds will likely result in the development of thin fresh wind slabs. These slabs are expected to be most sensitive immediately lee of ridge-crest.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Increased winds Friday night and Saturday will add to the already large cornices that loom over many features, potentially increasing the likelihood of failure. Cornice failure has the potential to release slabs on slopes below.

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 11th, 2015 2:00PM