Archived

Avalanche Forecast

Apr 4th, 2017–Apr 5th, 2017

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

New snow, wind, warming, and rain will increase the avalanche danger on Tuesday. It's a good time to stick to conservative terrain.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: 15-25 cm of snow, 60+ km/h south wind, freezing level up to 1200 m.WEDNESDAY: Another 5-15 cm of snow throughout the day, 60 km/h south wind, freezing level around 1000 m.THURSDAY: Linger flurries with another 5-10 cm, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.FRIDAY: Mostly cloudy with isolated flurries, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.

Avalanche Summary

On Monday, two large cornice falls were reported, one of which triggered a size 2.5 persistent slab avalanche on the February weak layer on a northeast aspect at 1600 m. Explosive control north of Stewart produced numerous size 1-2 wind slabs and cornices on north and northwest aspectsOn Wednesday, expect the new storm slabs to be touchy at higher elevations with the ongoing potential for deeper avalanches on the February weak layer.

Snowpack Summary

Strong winds and 20-40 cm of new snow will form fresh storm slabs above 1200 m. At lower elevations, rain will weaken the snow and release loose wet avalanches in steep unsupported terrain features. On shaded aspects above 1300 m, the new snow is burying 20-30 cm of old storm snow. Elsewhere, a mixture of crusts and moist snow surfaces exist from recent melt-freeze cycles. The late February persistent weak layer continues to be a concern for triggering large avalanches. This combination of crust and weak facets is now down 100-150 cm. Recent snowpack tests at the May Creek area found moderate sudden results on the layer on a east aspect around 1200 m. The layer could still be triggered by light loads in shallow weak spots.

Avalanche Problems

Storm Slabs

20-40 cm of new snow and wind speeds exceeding 60 km/h will build very touchy storm slabs.

Use caution on open slopes and convex rolls Use conservative route selection, choose moderate angled and supported terrain with low consequence.Minimize exposure during periods of heavy loading from new snow and wind.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer from February produced several large human triggered avalanches at the end of March, and may still react in shallow areas. Heavy loads such as a storm slab avalanche or a cornice fall are also possible triggers.

If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3

Loose Wet

Rain at lower elevations will cause loose wet avalanches in steep unsupported terrain features.

Be cautious of sluffing in steep terrain.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 2