Avalanche Forecast

Issued: Mar 19th, 2021 2:00AM

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

Ryan Shelly, VIAC

Vancouver Island.

One avalanche reported in the Beauforts on Northerly terrain. No additional avalanches reported at this time.

Summary

Past Weather

A week long spring diurnal cycle ended with the arrival of Thursday's storm cycle which should hold Vancouver Island mountain ranges in a winter pattern for the next several days.

Weather Forecast

Friday: 20cm Snow to 40 cm Snow, (10cm Snow to 15cm Snow for North Island) Winds Strong from the SE (with Extreme SE wind gusts), Freezing level 900M Saturday: Less than 5cm snow throughout forecast area, Winds Light to Moderate from the WSW, Freezing level 850MSunday: 15cm snow to 30cm Snow. Winds Strong from the SSW (gusting to Extreme), Freezing level steady at 900M and spiking in late afternoon to 1,100M.

Terrain Advice

The spring melt freeze cycle is taking a break and we are returning to winter for a few days. By all indications, according to weather models, it looks to be quite a snowy weekend in store for Vancouver Island.Practice patience and allow time for new storm instabilities to stabilize prior to committing to any steep terrain.Plan routes and choose terrain that is low angle and supportive as you begin to venture into unmodified and uncontrolled snowpack and terrain.Identify and avoid travel either above or below cornice features.Adjust travel plans to ensure avoidance of slopes during warming and where rain events may occur at the Below Treeline elevation band over weekend.

Snowpack Summary

Storm snow and upper snowpack instabilities will be a priority hazard to manage over the storm cycle that won't let up until next week. Generally speaking, the midpack and lower snowpack are well settled despite several layers distributed throughout which are providing results to testing however showing limited actual reactivity in the field by ski/snowmobile traffic.

Snowpack Details

Surface: Fresh storm snow sitting on a variety of surfaces including melt freeze sun crust and soft snow on North aspects
Upper: Last weekends storm snow interface with old snowpack is bonding but showing reactivity in unsupported terrain
Mid: Well settled due to melt freeze cycle snowpack has undergone. Does include a melt freeze crust/small facet interface down 70cm
Lower: Well settled and dense. Does include a basal melt freeze crust/ facet interface down 120cm

Confidence

High - Dangerous avalanche conditions in areas that receive more than 20cm of snow, likely at higher elevations over the weekend. Thank you CMSilver90 for your Beaufort MIN Report!

Problems

Cornices

Very large cornices exist and continued snowfall, wind and high humidity continue to promote cornice growth. Cornice failures have the potential to over load the snowpack and trigger both new snow instabilities as well deeper instabilities. Expect the new growth to be fragile and when temperatures and freezing levels rise become suspected triggers in bigger avalanche events. Location: Many aspects at ridge top in the Alpine and Tree line. Possibility: Triggering of this avalanche problem is likely to very likely from light loads such as skiers/snowmobilers. Natural avalanches are possible to likely. Size: If triggered expect these avalanches to be large size 2, on isolated terrain features very large, size 3

Likelihood

Possible

Expected Size

1 - 1

Wind Slabs

Wind slabs will become a factor Friday in areas where precipitation arrives in excess of 20cm coupled with strong winds. The wind slab issue will become increasingly unstable on Sunday as an additional 20cm of snow to 30cms of snow is expected to arrive with strong winds. Found on predominantly Northerly and downwind aspects. This avalanche problem will overlie a variety of snow surfaces, including surface hoar in isolated areas and/or a firm melt freeze crust. Location: Many aspects and found in both the Alpine and Tree line. Winds are shifting direction over weekend which will contribute to reverse loading and essentially complicate terrain management due to availability of new light dry snow being relocated to many downwind aspects. Possibility: Triggering of this avalanche problem is likely to very likely from light loads such as skiers/snowmobilers. Natural avalanches are possible to likely. Size: If triggered expect these avalanches to be large size 2, on isolated terrain features very large, size 3 .

Likelihood

Possible

Expected Size

1 - 1

Storm Slabs

This new avalanche problem will develop Friday in areas that receive snow in excess of 20cm- sensitivity to triggering will increase over the course of the storm event. On isolated Alpine terrain expect this new snow to overly buried surface hoar. On solar aspects, expect the storm snow to overlie a melt freeze crust. Location: All aspects, Alpine and Tree line. Below tree line hazard is from above. Possibility: Triggering of this avalanche problem is likely to very likely from light loads such as skiers/snowmobilers. Natural avalanches are possible to likely. Size: If triggered expect these avalanches to be large size 2 (by Friday), on isolated terrain features very large, size 3.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Mar 20th, 2021 2:00AM