Avalanche Forecast

Issued: Apr 20th, 2018 4:12PM

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.

jlammers, Avalanche Canada

South Coast Inland.

Forecast snowfall amounts are extremely variable throughout the region. Pay close attention to how much snow falls in your riding area and be prepared to back-off to simple terrain.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Saturday: 10-20cm of new snow / Strong southwest winds / Freezing level at 1800mSunday: Clear skies / Light and variable winds / Freezing level at 1900mMonday: Clear skies / Light and variable winds / Freezing level at 2400m

Avalanche Summary

Explosive control work in the Duffey Lake area on Wednesday produced a size 3 persistent slab avalanche that propagated over 200 m wide, failing on the late March weak layer. This result was on a west to southwest aspect between 2100-2200 m. No new avalanches were reported on Thursday. I would expect expect a new round of wind slab activity on Saturday in response to new snow and wind. Naturally triggered loose wet avalanches, cornice falls and intermittent persistent slabs should be on your radar with warming and solar radiation forecast for Sunday and Monday.

Snowpack Summary

New snow and wind on Saturday are expected to form fresh wind slabs in upper elevation lee terrain. The new snow is expected to overlie settled storm snow on shaded aspects above 2000m and a melt-freeze crust in most other areas.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 50 to 100 cm. This layer is spotty in its distribution and has recently produced large and destructive avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.The mid and lower snowpack are well-settled and strong.

Problems

Wind Slabs

New snow and wind will promote new wind slab development in upper elevation lee terrain. Watch for triggering behind ridge crests and in gullies.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

Professionals are traveling cautiously due to a weak layer buried 50 to 100 cm. The layer is found in upper treeline and alpine terrain on shady aspects. Recent large avalanches have been reported in the north of the region on this layer.

Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep convexities or areas with a thin or variable snowpack.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Apr 21st, 2018 2:00PM