Avalanche Forecast

Issued: Mar 26th, 2018 9:00AM

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

VIAC Bill Phipps, VIAC

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Vancouver Island.

Summary

Confidence

High - Weather models in agreement and good field data

Travel & Terrain Advice

Travel in avalanche terrain is not recommended when the avalanche hazard is posted as high. Significant quantities of dense new snow are forecast to fall on a widespread weak layer from last weekend (surface hoar). Give avalanche paths and their runouts a wide berth as they have the potential to run further than one may expect during this forecast period even into paths that stretch down into lower elevation bands. Cornices will be additionally loaded and travel above and below then should be avoided. Dense low angled forests would be the place to be if you are heading out to play.

Avalanche Summary

Friday - Mt Washington avalanche control produced numerous soft slab avalanches up to size 1.5 on N-NE asp at treeline and below. Sunday - Ski cutting was still producing easy loose dry avalanches on steep N treeline terrain down approx 10 cm.

Snowpack Summary

Cold new snow fell Friday. The weekend saw small amounts of new snow with some isolated convective activity producing some graupel. The big story was widespread surface hoar that developed over Saturday night and remained intact at the end of Sunday on all aspects at treeline and below. Early Monday morning the next snow fall began over the entire forecast region, with greater quantities falling to the north (Mt Cain region).

Snowpack Details

Surface:

New snow over a suspected weak layer (surface hoar). Upper: Recent storm snow from last week, bonding moderate to the March 22 crust. Mid: Well settled. Lower: Well settled.

Past Weather

Nice new snow for folks fell Friday. The Weekend was a mixed bag of conditions with a little bit of new snow, large temperature fluctuations between day and night (-8 to +3 at times) and even a little convective activity and graupel. Winds were general light to moderate form the SW.

Weather Forecast

Significant new snow fall (potential mixed precip at lower elevations) with warm temperatures and strong SW winds Monday into Tuesday. Monday: 9 to 40 mm of new precip, winds moderate rising to strong SW, temps -3 to +2, freezing level 1200 rising to 2300 m overnight. Tuesday: 6 to 17mm of new precip, winds strong SW dropping to L W, temps +2 dropping to -3, freezing level 2300 dropping to 1000m. Wednesday: trace to new new precip, winds light to moderate N-W, temps -1 to -6, freezing level 700 to 1000 m.

Problems

Storm Slabs

An icon showing Storm Slabs
Significant quantities of new snow will fall on a suspect weak layer (surface hoar). Strong winds from the SW and warming temperatures will accompany this storm, increase the avalanche hazard significantly. Expect avalanches hazard to exist on all aspect in the alpine, treeline and also open below treeline features (especially N-E asp and crossloaded features where wind loading magnifies quantities). Triggering is likely to initiate naturally and is very likely with human activity up to size 3.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 3

Cornices

An icon showing Cornices
Additional load from the coming warm storm (Monday into Tuesday) will apply more weight to already large and fragile cornice features. Triggering has the potential to happen naturally and is very likely with human activity. Give these monsters a wide berth, both on top of and below, as they have the bulk to produce avalanches up to size 2-3 on N-E asp in the alpine and treeline zones.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

2 - 3

Valid until: Mar 28th, 2018 9:00AM

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