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Avalanche Forecast

Archived

Feb 25th, 2014–Feb 26th, 2014

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

Regions

Kootenay Boundary.

Don't let the good weather lure you into terrain with consequences. The snowpack remains complex. Avalanche danger can rise rapidly with full sunshine, especially on solar aspects.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The strong arctic ridge of high pressure that has been dominating the Interior Regions will begin to retreat on Wednesday, bringing warmer temperatures and rising freezing levels. Some disturbances in this flow will bring cloudy skies later tin the forecast period.Wednesday: Sunny and 0.0 degrees expected at treeline. Ridgetop winds will be light from the NW. Freezing levels 1300 m.Thursday: Cloudy with sunny periods and 0.0 degrees at treeline. Ridgetop winds 20 km/hr from the NW. Freezing levels near 1500 m.Friday: Cloudy with sunny breaks and light flurries. Treeline temperatures -9.0 and ridgetop winds will be light from the NE.

Avalanche Summary

Skier remote triggered avalanches are continuing to surprise people up to size 2, while an explosive control mission also showed several slab avalanches up to size 2.On Sunday, a skier triggered size 2.5 was reported. Party of three with two involved. Sadly RCMP reported one fatality and the other suffered serious injuries. The crown was near 100 cm deep and released near ridgetop in storm snow and then stepping down to the persistent weak interface and running a far distance through the trees. With forecast sun, the avalanche hazard will likely increase on solar slopes.Check out the Forcaster Blog! It shows a photo of a remote triggered size 3 last Friday in the southern part of the Kootenay-Boundary.

Snowpack Summary

Changing winds from the southwest-north may build fresh wind slabs on leeward slopes and new surface hoar formation 5-10 mm has been noted. Currently there is over a metre of recent storm snow that is sitting on a weak layer comprising of facets, surface hoar, melt-freeze crusts and any combination of these. The weak layer is widespread at all elevations and aspects and continued whumpfing and easy sudden planar snowpack test results are being reported. The storm slab continues to settle and become more cohesive allowing for longer fracture propagations and remote triggering from up to 200 m away, yikes! This persistent weak layer is expected to be a concern for some time; at all elevations and aspects. Treeline and below treeline elevations is catching many people by surprise.With forecast sunny periods, solar aspects will likely see moist snow during the day, then forming a crust overnight.

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.