Avalanche Forecast

Issued: Mar 12th, 2015 9:32AM

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

rbuhler, Avalanche Canada

South Columbia.

"The green light is off." Unusually warm conditions with periods of strong sun and periods of rain have weakened the upper snowpack. Avoid sun-exposed slopes on Friday afternoon. Check out our blog on warming: http://goo.gl/nS6uhF

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A ridge of high pressure should bring a mix of sun and cloud for Friday. Freezing levels are expected to reach around 2500m and alpine winds are forecast to be strong from SW by the end of the day. On Saturday, a weak storm system reaches the region. Models are currently showing 10-20mm between Saturday morning and Sunday morning. Freezing levels on Saturday are expected to stay around 2000m during the day but are forecast to fall to below 1000m by Sunday morning meaning rain may switch to snow at many elevations. During the storm, alpine winds are forecast to be strong from the SW. On Sunday, the storm should exit and a mix of sun and cloud can be expected with light winds.

Avalanche Summary

On Tuesday and Wednesday, several natural avalanches were reported to have released on the ground. These were on solar aspects and the largest was a size 3. Natural and skier triggered wet sluffing was also reported up to size 2. On Friday, sunny and warm conditions could produce similar conditions. Large avalanches have isolated potential to release on deep weak layers or the ground. Sluffing is expected from steep sun-exposed slopes and the triggering of wind slabs is possible in the alpine.

Snowpack Summary

A moist snow surface is being reported to around 2500m on solar aspects and to around 2000m on north aspects. The mid-February crust is buried down 10-30 cm and there is a weak layer of facets and/or surface hoar in the sandwich above the crust. The mid pack is well settled with a couple of persistent weak layers that continue to give hard or very hard results in snow profile tests. The late-Jan crust/surface hoar layer (up to 100 cm deep) and the mid-January surface hoar (80-120 cm deep) have gained significant strength and have been dormant for several weeks but now have the potential to wake-up with the current warm temperatures.

Problems

Wind Slabs

Wind slabs have developed on various aspects in the alpine. Warm temperatures and an underlying weak layer may increase the likelihood of triggering these wind slabs.

Use caution in lee areas in the alpine. Recent wind loading has created wind slabs.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Wet

Warm temperatures and sun may result in loose wet avalanches releasing from steep terrain.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Sluffs may trigger deeper instabilities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Where enough snow overlies the mid-Feb crust/facet layer, reactive slab avalanches are possible. There is also a concern for avalanches to step-down to deeper weak layers or the ground due to the unseasonably warm temperatures.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 13th, 2015 2:00PM