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Avalanche Forecast

Archived

Apr 19th, 2014–Apr 20th, 2014

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

Regions

Northwest Inland.

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

Confidence

Poor - Due to the number of field observations

Weather Forecast

Generally unsettled conditions are expected for the next three days and there may a lot of variation in conditions across the region. There is also uncertainty in the weather models regarding timing and amounts of precipitation. It currently looks like Sunday should be mostly dry with light precipitation expected for Sunday night. Monday should be mostly dry before more precipitation Monday night. A ridge of high pressure looks to build late-Tuesday or Wednesday.Sunday/Sun. Night: Precipitation 1-4mm, freezing level am: 1100m pm: 1500m, ridgetop wind: moderate SE-SWMonday: A mix of sun and cloud, light scattered precipitation, freezing level am: 1000m pm: 1400m, ridgetop wind: light variableMon. Night: Precipitation 5-10mm, ridgetop wind: light SETuesday: Precipitation 1-4mm, freezing level am: 1000m pm: 1400m, ridgetop wind: light variable

Avalanche Summary

Reports from the north end of the region on Friday include sluffing from steep sun exposed slopes and isolated slab releases from leeward features on ridge crests. 

Snowpack Summary

The new snow may sit on a melt-freeze crust, old wind slabs in leeward features, or dry snow in sheltered north facing terrain at higher elevations. Recent strong S through W winds have created wind slabs in leeward features. In some areas, there may still be a weak layer below the old storm snow, down roughly 50-80cm, but triggering of this layer has become stubborn or unlikely. Cornices are also large and potentially weak, particularly during periods of warming. The early February persistent weak layer is typically down 1.5 to 2m. Triggering of this layer has become unlikely but may still be possible with heavy triggers such as cornice falls or smaller avalanches stepping-down.

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.

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.