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Avalanche Forecast

Archived

Feb 27th, 2014–Feb 28th, 2014

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

Regions

Northwest Coastal.

Don’t let your guard down! The deeply buried weak layer may continue to be well preserved on shaded aspects. More info in the new blog post!

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

Overnight and Friday: The alpine inversion along the coast is expected to end overnight. We should see below freezing temperatures at all elevations during the day with Easterly winds in the alpine and strong Northeast outflow winds near the coast. Mostly clear with a chance of high thin cloud during the day.Saturday: Clear and cold with strong Northeast winds and alpine temperatures around -17. Very strong outflow winds near the coast.Sunday: Clear and cold with strong Easterly winds and alpine temperatures around -20.

Avalanche Summary

Moist or wet loose snow avalanches up to size 2.0 have been reported from Southerly aspects during periods of strong solar radiation. A couple of loose snow avalanches in motion triggered a 30-50 cm dry slab up to size 3.0. North aspects in the alpine continue to be the most likely slopes for triggering the February weak layer where it may be well preserved and allow for long fracture propagations resulting in very large avalanches.

Snowpack Summary

Strong solar radiation and warm temperatures have resulted in moist surface snow on all but shaded North aspects. Moist or wet loose snow has been releasing naturally from steep Southerly aspects. The early February weak layer continues to give moderate to hard sudden planar shears in snow profile tests down 50-100 cm in the North and down 100-150 cm in the South. No recent reports of whumpfing or remote triggering on this weak layer of crusts and facets. Forecast strong Northeast outflow winds may continue to develop wind slabs in areas that still have snow available for transport. Basal facets and/or depth hoar remain a concern in shallow snowpack areas in the northern part of the region. Cornices are also large and may become weak if northerly winds start to undercut them.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.