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Avalanche Forecast

Archived

Apr 22nd, 2014–Apr 23rd, 2014

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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.

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 [email protected]

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 Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.