Avalanche Forecast

Issued: Mar 29th, 2021 2:00AM

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

Ryan Shelly, VIAC

Vancouver Island.

Small Loose wet avalanches reported on steep solar facing terrain as daytime air temps rise up into Treeline elevation band.

Summary

Past Weather

Generally mild air temperatures and day time highs raised the freezing levels to Treeline over the past several days. The generally warm air temps have promoted a great deal of consolidation to the upper 1M to 2M of the Vancouver Island mountain snowpack. A returned cooling trend returns for the next 24hrs to 48hours.

Weather Forecast

A major storm and wind event on Sunday has redistributed snow and created a dynamic avalanche risk management problem as Extreme winds shifted from South to North throughout the storm event. Expect a returned cooling trend to return for the next 24hrs to 48hours. Monday: No snow expected throughout forecast area, Winds Moderate and gusting to Strong from the NW, Freezing level 850MTuesday: No snow expected throughout forecast area, Winds Moderate (gusting to Strong) from the NW, Freezing level 1,000M (except mid-North Island where Freezing Level will rise to 1300M)Wednesday: No snow expected throughout forecast area, Winds Light from the SW, Freezing level 1,550M

Terrain Advice

Wind slabs will be primary hazard for the next 24 to 48 hours.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 events (particularly Wednesday).

Snowpack Summary

Loading in the form of new snow and extreme winds has promoted wind slab development on North and South downwind terrain. The new snow rests on a generally well settled and firm snowpack.

Snowpack Details

Surface: 5cm to 25cm of soft new powder snow
Upper: Well bonded and dense moisture laden snowpack.
Mid: Well settled due to melt freeze cycle snowpack has undergone.
Lower: Well settled and dense.

Confidence

Moderate - Weather models in agreement. Limited public observations submitted to VIACS and/or MIN at Avalanche.ca

Problems

Cornices

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 as deeper instabilities. Expect the new growth to be fragile and when freezing levels rise they will become suspect trigger points for large avalanche events. Location: Many aspects at ridge top in the Alpine and Tree line. Possibility: Triggering of this avalanche problem is possible to likely from light loads such as skiers/snowmobilers. Natural avalanches are unlikely to possible. 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

Loose Wet

Loose wet avalanches could become a factor on Wednesday as air temperatures will rise to the Alpine for the first time in over 72hours. A good deal of light dry powder snow will begin to undergo a melting trend for the first time on Wednesday which could result in naturally occurring loose wet avalanches on steep terrain. Location: Steep unsupported Terrain at Alpine and Tree line. Possibility: Triggering of this avalanche problem is possible to likely from light loads such as skiers/snowmobilers. Natural avalanches are unlikely to possible. Size: If triggered expect these avalanches to be large size 1, on isolated terrain features large, size 2 .

Likelihood

Possible

Expected Size

1 - 1

Wind Slabs

Wind slabs could become a factor Monday and into Tuesday in areas where precipitation arrived Sunday in excess of 20cm coupled with Extreme winds and a lower freezing level. Found predominantly on downwind aspects, the location of the wind slab will be found on Northerly and Southerly facing terrain due to extreme winds and reverse loading on the weekend. Moving into the early portion of the week, consistently Strong North flowing wind will promote wind slab development on Southerly facing terrain. This avalanche problem overlies a variety of snow surfaces, mostly a wet upper snowpack surface or a firm melt freeze crust (depending on elevation and aspect). Location: North and South facing aspects, by Tuesday, expect Southerly aspects to become a more likely area for triggering of wind slabs. The wind slabs will be found in both the Alpine and Tree line elevation bands. Possibility: Triggering of this avalanche problem is possible to likely from light loads such as skiers/snowmobilers. Natural avalanches are unlikely to possible. 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

Valid until: Mar 30th, 2021 2:00AM