Avalanche Forecast

Issued: Apr 23rd, 2021 2:00AM

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

Ryan Shelly, VIAC

Vancouver Island.

No new avalanches reported or observed.

Summary

Past Weather

Double digit air temperatures persisted up to the Alpine elevation band furthering the overall reduction in snow volume across Vancouver Island. Daytime heating and limited overnight cooling have formed a very moisture laden snowpack.

Weather Forecast

Friday: less 1cm Snow and up to 5cm Snow for North end of Forecast region, Winds light from the South, Freezing level 1,700 meters Temps at 1500 meters begin at +3 and drop to 0 degrees late afternoon.Saturday: 5cm Snow to 10cm Snow, Winds light from the South, Freezing level 1,350 meters. Temps at 1500 meters up to -1 degrees.Sunday: 10cm Snow to 15cm Snow (less than 5cm Snow for South end forecast region), Winds light from the ESE, Freezing level 1,400 meters. Temps at 1500 meters -1 degrees.

Terrain Advice

Please respect the current closures at Mount Washington, no access is permitted at anytime on the ski areas slopes or terrain.Avoid travelling both above and below cornices.

Snowpack Summary

Vancouver Islands mountain ranges have been subjected to a great deal of heating. Weather stations are reporting between 30cm to 40cm of snow volume reduction over the past week at the "near" Treeline elevation band. While melting is ongoing, the cooling trend over the next several days will "bridge" and consolidate the water laden upper snowpack. The question remains, to what extent the cooling refreezes these layers as the freezing level sits around the 1,500M elevation band through the weekend.

Snowpack Details

Surface: Firm upper snowpack surface softening mid-day with air temperature increase (Northern portion of forecast region may receive 5cm Snow and 5mm Rain at below treeline elevation band)
Upper: Firm/moisture laden snowpack that contains several near isothermal (water laden) layers/interfaces (should begin to refreeze over cooling period these next several days)
Mid: Well bonded midpack that includes several ice crust layers
Lower: Well settled and dense.

Confidence

Moderate - Cooling and "barely" below zero degree air temps return to mountain top. Is it enough to refreeze the water laden layers? Remain aware and conduct appropriate assessments prior to "stepping out" into large terrain features.

Problems

Cornices

Expect Cornices to remain highly unstable as they continue to collapse and fall with major (above zero degrees ) air temperatures. The probability of natural cornice failures occurring during the day are near certain. Location: Predominantly north aspects at ridge top in the Alpine and Tree line. Possibility: Triggering of this avalanche problem is possible. Natural avalanches are unlikely. Size: If triggered expect these avalanches to be small size 1, on isolated terrain features large, size 2

Likelihood

Possible

Expected Size

1 - 1

Loose Wet

The loose wet avalanche problem will remain an issue as overnight temperatures will remain above zero degrees up to treeline elevation, expect south facing terrain to become rapidly unconsolidated earlier in the day as temps rise and the sun begins to directly radiate onto solar surfaces. Location: South Aspects at all elevations Possibility: Triggering of this avalanche problem is possible from light loads such as skiers, particularly in areas that receive Rain instead of Snow (e.g. Below Treeline Elevation band). Natural avalanches are unlikely. Size: If triggered expect these avalanches to be small size 1, on isolated or extreme terrain features up to Size 2.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Apr 24th, 2021 2:00AM