Avalanche Forecast

Issued: Apr 18th, 2014 8:33AM

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

Peter, Avalanche Canada

Kootenay Boundary.

Check out this Forecasters Blog post for more info on how to manage risk during the spring. Here's a quote: "resist the urge to rely on danger ratings alone". Conditions change rapidly at this time of year and you need to stay tuned in locally.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

Saturday: Cloudy with sunny breaks and a chance of showers or flurries. The freezing level rises to around 2000 m and ridge winds are moderate to strong from the S-SW. Sunday: A mix of sun and cloud. The freezing level is around 2000 m and ridge winds are moderate from the west.Monday: Cloudy with sunny breaks and a chance of showers. The freezing level jumps up to around 2600 m. Wind are moderate from the south.

Avalanche Summary

There are no reports of recent avalanche activity, but my guess is that this is due to the lack of reporters and not the lack of activity. Expect loose wet activity in steep terrain and the possibility of storm/wind slabs in higher terrain. Last Sunday there was a report of a size 2.5 natural deep persistent slab in the Rossland Range in response to strong solar radiation and warm temperatures. This avalanche released on a steep southeast aspect at around 2100 m and likely failed on the mid February weak layer. It's a good reminder of the potential for large deep avalanches under certain conditions.

Snowpack Summary

Considerably more snow than forecast fell on Thursday and into Friday. Some areas may have received 40+ cm of snow, with a snow line somewhere around 1500-1600 m. This new snow may not initially bond well to the underlying snow surface, which is probably a hard crust in many places. Moderate southwesterly winds have likely formed new wind slabs in exposed lee and cross-loaded terrain near ridge crests. The late January/early February persistent weak layer is deeply buried but could still wake up during periods of heavy precipitation (especially rain) or significant warming and solar radiation. Cornices are large in some areas and should be given a wide berth.

Problems

Storm Slabs

Weaknesses may exist within or under the new storm snow. Triggering is more likely in steep wind loaded terrain, especially where the new snow overlies a hard crust.

Use ridges or ribs to avoid pockets of wind loaded snow.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

Expect widespread loose wet activity on steep sun exposed slopes.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

This problem is unlikely but should remain on the radar. We could see this wake up again this weekend with forecast warming and strong solar radiation.

Be aware of the potential for large, deep avalanches due to the presence of buried persistent weak layers.>Use caution on big alpine slopes, especially around thin areas that may propagate to deeper instabilities.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Apr 19th, 2014 2:00PM