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Avalanche Forecast

Archived

Jan 12th, 2018–Jan 13th, 2018

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

Jasper.

Be on your game for the weekend. Persistent slabs in exposed areas make it difficult to travel with confidence. Watch for increasing west winds that may further develop windslabs and rising temperatures that may allow for easier triggering.

Weather Forecast

A ridge will reach the coast Friday and bring warmer, moist air to the  Jasper region through the weekend. Alpine temperatures will be inverted and reach -6C on Saturday with a chance of a few flurries in the AM, watch for West winds to increase to 15km/h. An increase in the freezing levels to 2200m is called for Sunday as West winds to 20km/h.

Snowpack Summary

10-15cm of recent snow has blown into thin windslabs TL and above. Old slabs 10-30cm deeper sit on a weak layer of facets or surface hoar TL and above. In sheltered areas this new snow sits a faceted upper snowpack at all elevations. A strong mid snowpack crust is providing strength but is weakening. The lower snowpack continues to lose strength.

Avalanche Summary

Yesterday, besides a few small windslabs and sluffs from alpine terrain, a sz 2 slab 20cm deep and 50m wide likely failed on the Dec 18 persistent layer. This shallow slab ran a few meters before stepping down another 40 cm (likely through weak facets to the November 27 midpack crust). All of this ran 70m to a cliff triggering a small slab below.

Confidence

Due to the number of field observations on Friday

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.

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.