Archived

Avalanche Forecast

Jan 20th, 2016–Jan 21st, 2016

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

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

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: Northwest Coastal.

Thursday's storm could be enough trigger a widespread natural avalanche cycle. We could see surprising avalanches in "safer" area like lower angle and forested slopes. Keep your guard up.

Confidence

High

Weather Forecast

Tonight and Thursday: 15-25 cm of snow. The freezing level is 600-1000 m. Winds are strong from the South. Friday: Cloudy with flurries. The freezing level is near 600-800 m and winds are moderate from the SW. Saturday: Mainly cloudy. The freezing level is near valley bottom (or 500 m) and winds ease to light.

Avalanche Summary

Numerous avalanches were reported in the region on Monday and Tuesday. Reports included widespread activity up to size 2 north of Stewart and a natural avalanche cycle up to size 3.5 northwest of Terrace. Several skier triggered avalanches and remotely or sympathetically triggered avalanches up to size 2 were also reported. Most recent avalanches released on the Jan 9 surface hoar layer down 30-80cm. The majority of these avalanches were reported on north aspects, but there were avalanches on all aspects and elevation bands.

Snowpack Summary

Recent storm snow amounts have been variable across the region, but generally 40-60cm have accumulated since January 9th when the most recent surface hoar was buried. Below that is another surface hoar layer down 60-80cm. Remote triggering, whumpfing, and sudden "pops" shears are all indications that both these layers could propagate well if triggered. Deeper persistent weaknesses buried in December have the potential to wake-up to heavy loading, rapid warming, or avalanches stepping-down. Recent strong southeast winds have loaded leeward features on west through north aspect slopes, and scoured leeward slopes.

Avalanche Problems

Wind Slabs

New snow and strong southerly winds should combine to create deep pockets of wind slabs in lee and cross-loaded terrain. Once moving, these wind slabs could step down to persistent weaknesses in the upper snowpack.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Minimize overhead exposure; avalanches triggered by windloading may run further than expected.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Persistent Slabs

Incoming snow on Thursday could be enough to tip the scales and produce a large avalanche cycle on the January 9th surface hoar interface. Some slides may step down to deeper weaknesses.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Be careful with low angle slopes that may not normally be a concern.>Stick to simple terrain and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 2 - 6