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Avalanche Forecast

Archived

Dec 27th, 2013–Dec 28th, 2013

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

Regions

Northwest Inland.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Saturday: Cloudy with flurries or periods of snow developing later in the day – 5-10 cm. The freezing level is at valley bottom and winds are light to moderate from the west-southwest. Sunday: Mainly cloudy with a chance of flurries. The freezing level is near valley bottom but there is a chance of an above freezing layer near 1500 m. Winds are light from the W-SW. Monday: Periods of snow. The freezing level is near valley bottom and winds are light to moderate from the SW.

Avalanche Summary

No new avalanches have been reported, but observations are very limited. Areas with heavier recent snowfall likely experienced a natural avalanche cycle on Thursday. Rider triggering remains a concern in steeper terrain and wind loaded features, primarily at and above treeline.

Snowpack Summary

Storm snow totals in the region are around 40-50 cm, with moist or wet snow below treeline. Periods of moderate to strong W-SW winds were likely over the past couple days. Expect dense wind slabs in exposed lee terrain and cross-loaded features. Between 40 and 80 cm of snow sits on a crust that extends up to treeline and possibly beyond. This interface was "popping" under easy loads in snowpack tests a few days ago. A new surface rain crust will probably form at lower elevations as temperatures cool tonight. Deeper in the snow pack a layer of facets/surface hoar formed in early December can be found in the top 100cm in the Ashman. The mid and lower snowpack is still structurally weak and faceted. Depth hoar and an early season crust exist near the ground.

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.