Avalanche Forecast

Issued: Mar 4th, 2017 6:02PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs.

Avalanche Canada cgarritty, Avalanche Canada

Heavy snowfall and strong winds have blanketed the region with touchy storm slabs. Conditions on Sunday will be primed for human triggered avalanches.

Summary

Confidence

High -

Weather Forecast

An unsettled pattern opens the door to a string of relatively small low-pressure systems that should deliver modest snowfall to the region through the forecast period. Cold air currently in place will help to keep freezing levels low, at least through Tuesday afternoon. All bets are off Wednesday, when the weather models show an influx of moist warm air that will likely push the freezing level up towards 2000m and deliver 10 to 30mm of precipitation.SUNDAY: Overcast skies, freezing level near valley bottom rising to 500m in the afternoon, moderate SW wind, 1 to 5cm of snow.MONDAY: Overcast skies, freezing level around 500m, moderate SW wind, 1 to 5cm of snow.TUESDAY: Overcast skies, freezing level rising to about 700m in the afternoon, potentially pushing to 1500m in the evening, moderate to strong SW wind, 1 to 5mm of precipitation expected.

Avalanche Summary

Reports from Friday include several storm slab and wind slab observations from Size 1-2.5. These avalanches were triggered naturally as well as with ski cutting and explosives. All aspects seemed to share fairly equal representation and crown fractures have generally been limited to the depth of our recent storm snow.On Thursday control work produced storm slab avalanches to size 1.5 on NE, E and SE facing slopes. Reports from Wednesday include numerous natural, skier and explosive triggered storm/wind slab avalanches up to Size 2.Looking forward, we should see a decline in natural avalanche activity while the potential for human triggering at the full depth of our recent storm snow persists for a few more days.

Snowpack Summary

A wide-ranging 35 to 100cm of snow has fallen in the last week. The snowfall was initially accompanied by strong northwest winds, though these have since shifted to the SW. These winds have promoted the formation of touchy storm and wind slabs in lee areas at higher elevations. The new snow has been bonding poorly to a sun crust on previously sun-exposed slopes, as well as faceted surface snow and large surface hoar on shaded aspects. A variety of crusts and thin surface hoar layers in the upper snowpack have been an increasing concern as new snow and wind have loaded the upper snowpack. Areas with a shallow snowpack (less than around 170 cm) generally have a weak snowpack structure with a deep persistent weakness of facets near the ground. There are a number of great MIN reports from Thursday and Friday here: http://www.avalanche.ca/mountain-information-network/submissions/

Problems

Storm Slabs

An icon showing Storm Slabs
A week of stormy weather has fueled a storm slab problem that is especially touchy in wind exposed terrain. Weak layers at the previous snow surface mean that cautious terrain selection remains key while the new snow gradually bonds to the surface.
Think carefully about the increased risks involved in traveling into wind exposed terrain.Use cautious decision making and select conservative terrain this weekend.Keep in mind that human triggering potential persists as natural avalanching tapers off.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Mar 5th, 2017 2:00PM