Avalanche Forecast

Issued: Dec 4th, 2018 3:00PM

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

ghelgeson, Avalanche Canada

Lizard-Flathead.

Strong to extreme northwest wind Tuesday night is expected to create fresh wind slabs in the alpine which may continue to fail naturally Wednesday. Wind slab avalanches in motion may step down to deeply buried weak layers producing large avalanches.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

The high amplitude ridge sitting off the BC Coast is expected to deflect any potential storm systems away from the province this week. The forecast period is marked by cooler temps, clear skies and no significant precipitation with no change expected for the foreseeable future.TUESDAY NIGHT: Freezing level at valley bottom, light southerly wind at most elevations, strong to extreme northwest wind at ridgetop, no significant precipitation expected. WEDNESDAY: Broken cloud cover, freezing level at valley bottom, light variable wind, no significant precipitation expected. THURSDAY: Clear sky, freezing level at valley bottom, light variable wind, no significant precipitation expected.FRIDAY: Clear sky, freezing level at valley bottom, light southwest wind at low elevations, moderate northwest wind at ridgetop, no significant precipitation expected.

Avalanche Summary

No new avalanche activity to report from Monday. On Sunday a human triggered avalanche was reported in Cornice Bowl. We received some updated information about the size of the avalanche. It's been determined that the northwest facing feature at 2300 m produced a size 2 avalanche that ran on the early November crust. The crown was 30 to 40 cm deep, approximately 20 m wide and 300 m in length. Check out the initial report here. Explosive control also triggered a few storm slabs up to size 2 from northeasterly aspects 1800-2000 m. If you're in the backcountry and have observations to share, please post to the Mountain Information Network.

Snowpack Summary

Up to 55 cm of recent snow sits on a combination of crust and surface hoar. The crust is most prevalent at and above treeline and is likely most problematic on north facing features, especially those that are large and planar in nature.The surface hoar is tricky to pin down because it is quite spotty in distribution, but it appears to be most prevalent on sheltered slopes at and above treeline. At the bottom of the snowpack lies another crust with weak sugary facets around it. There is a great MIN Report here that provides a good visual representation of the current snowpack.At treeline the average snowpack depth is 80 cm, with only thin coverage at lower elevation.

Problems

Wind Slabs

Strong to extreme winds in the alpine Tuesday night are expected to create fresh wind slabs. Wind speed is expected to diminish overnight, but wind slabs will likely remain sensitive to human triggering Wednesday.

Use caution in lee areas. Recent wind loading have created wind slabs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Persistent Slabs

55 cm of recent storm snow is consolidating into a slab above buried weak layers. Human triggering likely remains possible, especially in steep unsupported terrain.

Be aware of the potential for large avalanches due to the presence of a persistent slab.Back off if you encounter signs of instability like whumphing, shooting cracks or recent avalanches.Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 5th, 2018 2:00PM