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Avalanche Forecast

Archived

Feb 9th, 2013–Feb 10th, 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 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

Cariboos.

Intensity from the sun can make the snowpack weaken and avalanche danger rise rapidly. Be aware of this and keep travel options open to adjust with this change.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

Sunday: As the ridge shifts to the East, the region will remain under a NW flow which will keep alpine temperatures cooler but under high solar influence. However, some areas may still see high cloud cover through the day. Ridgetop winds will blow Light out of the North. Treeline temperatures around zero degrees and freezing levels rising to 1600 m.Monday: The dominating ridge will be to retreat to the South allowing a more zonal flow to set up off the coast. Ridgetop winds will switch and blow moderate from the NW. Treeline temperatures will be near -2 and freezing levels near 1100 m.Tuesday: A cold front embedded in the zonal flow will move through the region bringing moderate precipitation amounts accompanied by strong winds from the SW. Treeline temperatures will fall to -5 and freezing levels will be near 1200 m.

Avalanche Summary

Over the past couple of days a natural avalanche cycle was seen in some of the SE areas of the region. Crowns were 40-50 cm deep and avalanche size was 2-2.5. There was also a report of Natural Cornice fall triggering a slab size 2.5 on the slope below. This occurred on an East aspect and failing on the Jan. 23rd crust.

Snowpack Summary

20-40 cm of new snow is sitting on wind slabs and recently buried weak layers. Old storm snow has settled into a dense slab that sits on a persistent weak interface deeper (40-80 cm down) in the snowpack. Crusts, surface hoar and facets that were buried around January 23rd are acting as those weak interfaces. Use extra caution on large open slopes, cutblocks and convex rolls at and below treeline where buried surface hoar may be preserved.Wind slabs continue to develop and stiffen on lee slopes and behind terrain features like ridgelines and ribs. There is a lot of new snow out there available for wind transport.The mid-pack is generally well settled and strong and the average snowpack depth at treeline elevations is near 200 cm. Watch the duration and intensity of the sun in your local riding area, it may weaken the upper snowpack. Cornices have grown and could threaten the slopes below.

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.