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Avalanche Forecast

Archived

Apr 19th, 2014–Apr 20th, 2014

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

Regions

Northwest Coastal.

This bulletin was created using very limited field data. If you are out in the mountains, please send your observations to [email protected]

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Light precipitation is expected for the north coast on Sunday. Unsettled conditions are expected for Monday and Tuesday resulting in light scattered showers and a mix of sun and cloud. Overnight freezing levels will vary depending on local cloud cover.Sunday/Sun. Night: Precipitation 5-8mm, freezing level am: 900m pm: 12000m, ridgetop wind: moderate-strong S-SWMonday: A mix of sun and cloud, light scattered precipitation, freezing level am: 800m pm: 1200m, ridgetop wind: light SE-STuesday: A mix of sun and cloud, light scattered precipitation, freezing level am: 800m pm: 1100m, ridgetop wind: light SW-W

Avalanche Summary

Reports from Friday of sluffing from steep sun exposed terrain features and isolated slabs releasing from leeward features on ridgecrests.

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 is 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 can be found. Recent strong S through W winds have scoured windward slopes and created wind slabs in leeward slopes. In wind sheltered areas, the new storm snow has formed a storm slab which typically sits on a firm crust. 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 layer causing very large, destructive avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.