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Avalanche Forecast

Archived

Mar 14th, 2017–Mar 15th, 2017

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

Regions

North Columbia.

Rapid loading and warm temperatures are a recipe for HIGH danger. Conservative terrain use at all elevations is essential this week. Avoid overhead hazard and choose simple terrain!

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Warm temperatures and high freezing levels continue with moderate winds and heavy snow on Wednesday. WEDNESDAY: Another 15-30cm of fresh snow (above 1700m), accompanied by moderate south winds. Freezing levels near 1900m. THURSDAY: Sunny breaks with flurries (up to 5cm) accompanied by moderate southwest winds. Freezing levels dropping to 1200m. FRIDAY: Cloudy with isolated flurries (5cm) with moderate southwest winds. Freezing levels near 1200m.

Avalanche Summary

On Monday a widespread storm slab natural avalanche cycle to Size 2.5 was reported on a range of elevations and aspects. Wet slabs and loose wet avalanches were also reported below treeline. On Sunday, several large avalanches (up to Size 4) were reported with artillery control in Glacier National Park, some running full path to valley floor.On Sunday several small natural storm slab avalanches were reported near Revelstoke below treeline. Use extra caution for the time being in what is normally a 'safer' elevation band. See here for the excellent and informative MIN post.

Snowpack Summary

Around 40-60cm of fresh snow has fallen over the past several days (with light to moderate southerly winds). Touchy storm slabs can be found at all elevations with weaknesses within and under this recent snow. Warming temperatures on Sunday into Monday has resulted in moist (read: heavy) surface snow up to 2100m in most areas, and unstable wet snow below treeline.All this new snow is bonding slowly to faceted snow as well as isolated small surface hoar in sheltered areas and a thin sun crust on steep southerly aspects.The persistent weakness buried late-February is now down 80-140 cm, and is composed of a thick rain crust as high as about 1800 m, sun crusts on steep southerly aspects, and spotty surface hoar on shaded aspects. Recent reports show the bond to this interface slowly improving.The mid and lower snowpack are well settled and stable in deeper snowpack areas, but may be weak and faceted in shallow areas. The deep mid-December facet layer still lingers in the northern part of the region near Valemount.

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.

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.