Avalanche Forecast

Issued: Feb 25th, 2020 1:00AM

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

Ryan Shelly, VIAC

Vancouver Island.

Monday February 24th: 1 Skier triggered avalanche was initiated on Buck's run on NE aspect on Mt Washington backcountry on unsupported leeward terrain feature (Soft Slab on rain Crust). The fracture height was approximately a 30-40 cm and 20-25 Meters wide (therefore a size 1 to 1.5 avalanche) Equipment was lost however no complete burial and no injury. Sunday February 23rd: Mt Washington Avalanche control reported avalanche initiation of storm snow/wind loaded features (soft slab) on most recent upper rain crust layer

Summary

Past Weather

A low pressure system will deliver light and consistent precipitation to Vancouver Island over the next several days to the north east of the island has persisted but is forecast to come to an end late Friday. Saturday an expected incoming weather systems will begin to deliver snow and wind, with a subsequent stronger weather system arriving Sunday.Friday: Trace amounts of snow late in the day, Winds Moderate from the South West, Freezing levels to 1000 meters.Saturday: 5 to 10 cm of snow, Winds Strong from the South West, Freezing levels to 1000 meters.Sunday: 15 to 25 cm of snow, Winds Strong from the South West, Freezing levels 1000 meters.

Weather Forecast

A low pressure system will deliver light and consistent precipitation to Vancouver Island over the next several daysTuesday: 2 to 10 cm of snow, Winds Moderate to Strong and reducing to Moderate winds again in afternoon from the South West, Freezing levels to 1000 meters.Wednesday: 4 to 14 cm of snow, Winds Moderate from the South West, Freezing levels to 1000 meters.Thursday: 3 to 7 cm of snow (possibility of 6mm of rain at Treeline and Below Treeline elevation, Winds Moderate from the South West, Freezing levels 1400 meters.

Terrain Advice

Careful route find and snow-pack evaluation are paramount during periods of sustained moderate snowfall and strong winds.Avoid traveling both above and below cornice features.Careful and cautious route finding when entering into or over convex rolls or steep features.

Snowpack Summary

The upper snowpack contains a melt freeze crust found down anywhere from 20-40cm from the snowpack surface. This melt freeze crusts has been responsible for a number of skier triggered avalanches in the past 48hrs. Expect this layer/interface to continue to cause avalanches in the size 1-2 category which are large enough to fully bury a skier or sledder. The incoming precipitation these next 72 hours, coupled with strong winds should continue to exarcerbate this upper snowpack issue, particularly in leeward or down wind areas where snow loading will occur.

Snowpack Details

Surface: Light low density snow
Upper: A supportive and reactive melt freeze crust down from 15 to 30 cm
Mid: A variety of old crusts can be found.
Lower: well settled and dense

Confidence

High - Weather models in agreement, Moderate field data available, insufficient Weather station data.

Problems

Loose Wet

Moderate Rain events at lower elevation. On Thursday Rain up to Treeline elevation bands could exacerbate new storm snow instabilities with additional rain loading of fresh snow. In addition to Rain events over Wednesday and Thursday, Daytime warming and the suns effect on surface snow may cause snow to become unconsolidated on south aspects. This avalanche problem when triggered is likely to remain small, but on isolated terrain features that are steep and direct solar, these features will promote a small avalanche to gain mass and result in a large, size 2. Expect this avalanche problem to become more prevalent once the incoming rain arrives in addition to rising air temperature (particularly Wednesday and Thursday). Location: On all south aspects and found at Below Treeline and Treeline elevations. Possibility: Triggering of this avalanche problem is possible from light loads such as skiers. Natural avalanches are unlikely. Size: If triggered expect these avalanches to be small, and on isolated terrain features large, size 2.

Likelihood

Possible

Expected Size

1 - 1

Wind Slabs

Moderate precipitation in the form of storm snow coupled with moderate winds on Tuesday into Wednesday could promote wind slab instabilities (particularly in leeward or down wind areas on Vancouver Island. Expect all Alpine environments in leeward/down wind terrain to be likely areas to trigger a wind slab avalanche on Tuesday and Wednesday.

Likelihood

Possible

Expected Size

1 - 1

Storm Slabs

New snow from incoming storm system will rapidly fall on a variety of surfaces. Expect this new avalanche problem to be initially very touchy to light triggers such as skiers. Location: All aspects and at all elevations. New Storm snow may fall as rain at the Below Treeline Elevation Band on Tuesday, Wednesday and Thursday Possibility: Triggering of this avalanche problem is very likely to likely from light loads such as skiers. Natural avalanches are possible to likely. Size: If triggered expect these avalanches to be small - large (up to size 2) OR on avalanches could appear on isolated terrain features (very large, size 3).

Likelihood

Possible

Expected Size

1 - 1

Valid until: Feb 26th, 2020 1:00AM