Avalanche danger rising in the backcountry

Warming and heavy snow will overload the snowpack and drive the danger to HIGH. Surprising avalanche results may occur given our current snowpack. Conservative terrain use is essential this week and avoid overhead hazard.

Avalanche Summary

On Monday natural storm slabs to Size 2 were reported above 2400m on south and east aspects.

On Sunday afternoon a rider-triggered Size 2.5 persistent slab avalanche was reported near Golden. Average slab depth was 50cm on a steep north facing aspect near 2300m.

Several storm and persistent slab avalanches to Size 3 were also reported on Sunday – most activity was above 2300m on a variety of aspects.

Snowpack Summary

Around 20-50cm of fresh snow in the past several days has fallen with light to moderate southwest winds. These winds have formed touchy slabs at upper elevations with multiple weaknesses within and under this recent storm snow.

Warming temperatures on Sunday into Monday has resulted in moist (read: heavy) surface snow up to 2000m in most areas, and some unstable snow below treeline.

All this snow is bonding poorly to weak faceted snow and small surface hoar on sheltered shady slopes, and/or a thin crust on southerly aspects.

The persistent weakness buried mid-February is lurking down 70-120 cm and composed of a thick rain crust as high as about 2000 m, sun crusts on steep southerly aspects, and spotty surface hoar on shaded aspects. This layer has produced easy results in recent snowpack tests and has proven especially reactive on steep southerly aspects.

Several deeper persistent weaknesses also remain a concern, including surface hoar buried early-February (around a metre deep), and mid-January (well over a metre deep primarily in the northern Purcells). The november crust and basal facets are still sensitive in shallow, rocky start zones.

COMPLETE UPDATES: http://www.avalanche.ca

Weather Forecast

Warm temperatures and high freezing levels continue with moderate winds and heavy snow on Wednesday.

WEDNESDAY: We’ll see 15-25cm of fresh snow (above 1700m), accompanied by moderate south winds. Freezing levels near 1900m.

THURSDAY: Sunny breaks with flurries (5-10cm) accompanied by moderate southwest winds. Freezing levels dropping to 1300m.

FRIDAY: Cloudy with isolated flurries (up to 5cm) with light to moderate southwest winds. Freezing levels near 1200m.

MORE WEATHER…

The Aleutian low anchored firmly over the Gulf of Alaska continues to steer south westerly flow into much of the southern BC today. A band of warm moisture originated from the tropics will bring another rainy to much of the southern BC this morning. Several disturbances are embedded in this stream of warm moistures. With the high freezing levels, snow will fall mainly at the alpine levels. Behind the first disturbance, freezing levels will drop over northern Rockies, Cariboos and northern Columbias tonight.

Another disturbance will move across BC south coast on Wednesday morning. Ahead of the disturbance, freezing levels over southern interior will remain around 1600 – 1800m for another day. Central interior and Northern Rockies will se a cooler airmass Wednesday.

The upper level trough broadens by Thursday, allowing the upper level flows over southern BC to become more zonal. Weak disturbances will bring light precipitations to the coastal regions while interior stay relatively dry for Thursday and Friday. Another organized low pressure system will approach the BC coast and deepen the upper trough on Saturday.

More wet weather forecast for southern BC this weekend…

Forecasts and graphics produced by the Meteorological Service of Canada (MSC)