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Avalanche Forecast

Archived

Feb 9th, 2019–Feb 10th, 2019

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

Regions

South Rockies.

Check out the AvCan South Rockies blog for advice on managing the persistent slab problem affecting the region. (Link Here)A Special Public Avalanche Warning is in effect in this region.

Confidence

Moderate -

Weather Forecast

Cold, dry, arctic air continues to dominate the weather pattern for the foreseeable future.SATURDAY NIGHT: Freezing level at valley bottom, around -25 C in the alpine, light variable northerly wind at valley bottom, light southerly wind at ridgetop, no significant snowfall expected.SUNDAY: Clear skies at dawn with cloud cover beginning to increase around lunch, freezing level at valley bottom, around -20 C in the alpine, light southerly wind at valley bottom, moderate southwest wind at ridgetop, no significant snowfall expectedMONDAY: Scattered cloud cover, freezing level at valley bottom, around -20 C in the alpine, light southerly wind at valley bottom, moderate southwest wind at ridgetop, no significant snowfall expected. A few centimeters of snow possible Monday night.TUESDAY: Scattered cloud cover, freezing level at valley bottom, around -15 C in the alpine, light variable wind at most elevations with moderate to strong southwest wind at ridgetop, a few cm of snow possible.

Avalanche Summary

A social media post from the Marten area of Elk Valley on Thursday describes touchy persistent slab conditions, with lots of smaller slabs releasing over the mid-January surface hoar layer. Check out the post here. Of note is the fact that this area was previously untracked, leaving the mid-January layer undisturbed. This is something to bear in mind as dry conditions persist and the motivation to step out of well-traveled terrain increases. Areas where this layer is undisturbed are far more likely to hold reactive persistent slabs.

Snowpack Summary

Above 1700 m, 25 to 35 cm of recent snow overlies a variety of surfaces, including feathery surface hoar crystals in shaded and sheltered areas, wind-affected snow in exposed terrain, and a melt-freeze crust on southerly aspects. Recent winds continue to redistribute loose snow and develop wind slabs. Below 1700 m, expect to find around 5-10 cm of low-density snow on a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 35 to 45 cm deep. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m but has been found up to 2200 m. The melt-freeze crust is found on south aspects at all elevations. This layer is the subject of our Special Public Avalanche Warning. A social media post from the Elk Valley Snow Shepherds from Wednesday does a great job of highlighting the issue. Check the link here.The middle of the snowpack is generally consolidated. The bottom half of the snowpack is unconsolidated and composed of weak and sugary faceted grains. The basal snowpack is becoming even weaker under prolonged cold temperatures, especially in thin snowpack areas.

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.

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.