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Avalanche Forecast

Archived

Jan 24th, 2018–Jan 25th, 2018

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

Regions

South Rockies.

Recent storm snow and wind are adding to a snowpack with several buried weak layers. Best to stick to conservative terrain choices, avoid wind-loaded areas, and back off if you see classic warming signs like whumpfing or cracking.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Light flurries. Accumulation 1-4 cm. Ridge wind strong, southwest. Temperature -4. Freezing level lowering to valley bottom.THURSDAY: Mix of sun and cloud, flurries. Accumulation trace. Ridge wind strong, southwest. Temperature -2. Freezing level rising to 1000 m.FRIDAY: Mix of sun and cloud, light flurries. Accumulation 1-5 cm. Ridge wind strong, southwest. Temperature -4. Freezing level valley bottom.SATURDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southeast. Temperature -8. Freezing level valley bottom.

Avalanche Summary

There have been no new reports of avalanches in the region since Saturday when explosive control in the Castle area produced several Size 2-2.5 storm slabs around 40 cm deep. Ski cutting in the same area produced numerous smaller (Size 1) releases also confined to the recent storm snow.The lack of activity can most likely be attributed to a lack of observations rather than snowpack conditions.  The snowpack in the region remains suspect with several buried weak layers displaying classic signs of instability such as whumpfing and cracking.A recent video posted to the Avalanche Canada South Rockies field team Facebook page paints a pretty clear picture https://www.facebook.com/avcansouthrockies/videos/1894352117306941/.

Snowpack Summary

Up to 30 cm of recent storm snow now covers both a new layer of feathery surface hoar in sheltered areas as well as sun crust on solar aspects buried mid-January, and about 30-50 cm below the surfaces lies the early-January surface hoar layer.About 60-80 cm below the surface a weak layer of feathery surface hoar crystals and/or sun crust buried mid-December is found at treeline and below treeline elevations. Near the base of the snowpack the weak early-season layer of rain crust and sugary facets buried late-November exists. Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread. Snowpack depths are also variable across the region and typically thinner in northern areas than in areas to the south.

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.

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.