Avalanche Forecast

Issued: Apr 22nd, 2014 9:14AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Loose Wet and Deep Persistent Slabs.

rbuhler, Avalanche Canada

Northwest Coastal.

Avalanche danger can rise quickly with afternoon warming and solar radiation. Deeply buried persistent weak layers may re-awaken during these periods.For more insight into spring danger ratings, check out this blog post.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

On Wednesday, the south of the region is expected to be mostly dry and sunny, and the north of the region is expected to be cloudy with scattered precipitation. Thursday should be mostly dry and sunny across the region with convective flurries. Warm temperatures with no overnight recovery are expected Wednesday and Thursday nights. There is the possibility of a weak storm system for parts of the region on Friday but it is uncertain.Wednesday: Clear in the south, cloudy in the north, scattered precipitation 0-4mm, freezing level am: 600m pm: 1200m, ridgetop wind: light variableThursday: Mostly sunny, freezing level am: 1200m pm: 1700m, ridgetop wind: moderate SEFriday: Unsettled conditions, freezing level am: 1300m pm: 1400m, ridgetop wind: moderate SE

Avalanche Summary

We received a report of a very large natural deep-slab avalanche east of Terrace on Monday. This avalanche occurred on a NW aspect at 1800m. The crown appears to be 1-2m deep meaning it likely released on the early-Feb weak layer. We are no longer receiving professional daily reports for the region so public observations are really appreciated right now. If you are out in the mountains, send your observations to forecaster@avalanche.ca

Snowpack Summary

Highly variable spring conditions are being reported in the region. At lower below-treeline elevations the snowpack is typically wet and isothermal. It has not been refreezing overnight and is melting quickly. Between roughly 1000 and 1500m, the snowpack has been undergoing daily melt-freeze cycles. The same conditions can be expected on sun-exposed slopes all the way to mountain-top. On higher elevation north-facing slopes, dry snow likely still exists. Recent strong S through W winds have scoured windward slopes and created wind slabs in leeward slopes. The early February crust/facet layer is typically down 1.5 to 2.5m. A smaller avalanche or a cornice fall may still have the potential to step down to this layer causing very large, destructive avalanches, especially during warm sunny periods.

Problems

Wind Slabs

Wind slabs from the weekend storm may still be sensitive to human-triggering. These formed in leeward alpine features from strong S-SW winds.

Use caution in lee areas in the alpine. Recent wind loading have created wind slabs.>Be cautious as you transition into wind affected terrain.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Loose Wet

Loose wet activity can be expected from steep features during periods of solar warming or rain. Isolated wet slabs may be possible under the same conditions where the recent storm snow is poorly bonded to the underlying crust.

Be cautious of sluffing in steep terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Deep Persistent Slabs

A deeply buried persistent weak layer still has the potential to produce very large avalanches and could be triggered by heavy triggers such as cornice falls or smaller avalanches stepping-down.

There is potential for large, deep avalanches due to the presence of buried facets and surface hoar.>Conditions have improved, but be mindful that deep instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 23rd, 2014 2:00PM