Archived

Avalanche Forecast

Dec 7th, 2015–Dec 8th, 2015

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

4: High

The avalanche danger rating below treeline will be high

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Regions: Kootenay Boundary.

Rapidly rising temperatures, heavy snowfall transitioning to rain at upper elevations and strong to extreme SW winds should make for dismal riding conditions, but if you do head into the backcountry it's time to avoid all avalanche terrain.

Confidence

Low - Due to the number of field observations

Weather Forecast

Tuesday morning delivers a strong warm front that is expected to push the freezing level as high as 2500m. This warm and moist subtropical air should also deliver heavy precipitation. The rain/snow line is expected to start near 1000m and then steadily rise through the day. We should be back to more seasonal temperatures by Wednesday afternoon. TUESDAY: 5 to 30mm of precipitation expected. Freezing level starting at 1000m, rising to 2500m. Strong to extreme SW winds expected. TUESDAY NIGHT: 20 to 50mm of precipitation, freezing level holding at 2500m. WEDNESDAY: 4 to 10cm of snow. Freezing level lowering to 1500m. Strong W/SW winds. THURSDAY: 2 to 5cm of snow. Freezing level beginning near 1000m, rising to 1500m. Moderate W/SW winds.

Avalanche Summary

On Saturday natural storm slab avalanches to size 2 were reported on East, North, and Northwest facing features between 1900 and 2100m. These were likely running on the early December surface hoar. On Sunday control work in the region produced numerous avalanches to size 2 on SW, S and SE facing aspects between 1900 and 2000m. Late Sunday we received a report from the Rossland range where a group of skiers triggered a size 2.5 avalanche on a north facing piece of terrain at 1700m. The avalanche initially failed at the Mid-November crust before stepping down to the ground. Thankfully, it sounds like everyone involved will be okay.

Snowpack Summary

Total snow depth in the region is between 100 and 175cm. Since Thursday December 3rd the storms have been impacting the region one after another. Total snowfall from these storms is between 30 and 70cm. This storm snow rests on a variety of old surface including loose faceted snow, the well advertised early-December surface hoar in sheltered locations at and below treeline, and a crust at upper elevations (especially on southerly aspects). The mid-November crust is just under the new storm snow and quite robust. It's been reported as being 1 to 8cm in thickness. A human triggered avalanche Sunday ran on this crust and we suspect it's just starting to wake up. The next few days should tell us a lot about this interface.

Avalanche Problems

Storm Slabs

Rapidly rising temperatures, heavy snowfall transitioning to rain and strong SW winds should make for a tricky Tuesday. Rapid settlement of the recent storm snow will likely result in a widespread avalanche cycle at all elevations.

The areas we usually consider safe at treeline may be some of the most volatile right now, as this is where the surface hoar is best preserved.>Avoid all avalanche terrain.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be aware of the potential for large, deep avalanches as the snowpack is saturated by rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5