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Archived

Avalanche Forecast

Jan 24th, 2015–Jan 25th, 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
3: Considerable
The avalanche danger rating below treeline will be considerable
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Northwest Coastal.

Intense loading from new wind and snow will add more stress to buried weak crystals, and very large avalanches remain a real concern. Conservative terrain selection remains critical.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

A steady pacific moisture stream is aimed at the North Coast, although the track of the system suggests the bulk of the precipitation will initially fall just to the south of the region. Sunday: Up to 10cm of snow at higher elevations / Extreme southwest winds / Freezing levels at 1400m Monday: Up to 15cm of snow at higher elevations / Strong southwest winds / Freezing levels at 1300m Overnight Monday and Tuesday: 15-20cm of snow / Strong southwest winds / Freezing levels at 800m

Avalanche Summary

Very heavy loading from snow, wind, and rain has resulted in a widespread natural avalanche cycle up to size 4.0 on Thursday. Reports from Wednesday include numerous wind slab and some step-down persistent slab avalanches in the Size 2-3 range, with isolated deep persistent slab avalanches up to size 3.5 from large alpine features. Below approximately 1000m numerous wet loose snow avalanches up to Size 2.5 were observed running in steep terrain. This pattern should continue throughout the forecast period.

Snowpack Summary

Heavy snowfall (with rain below approximately 1500-1000 m) and strong southwest winds have built fresh deep and dense storm and wind slabs. The slabs are likely 'upside down' with warm temperatures dropping moist dense snow on previous dry lower-density snow. A rain crust and/or surface hoar layer buried mid-January is down around a metre. Recent reports mention that this weakness has become 'electric' with recent heavy loading and has been responsible for much of the recent large avalanche activity. The November crust near the bottom of the snowpack is generally well bonded, but may 'wake up' with intense loading this week. There is potential for isolated very large and deep avalanches.

Avalanche Problems

Storm Slabs

Recent heavy loading from snow and wind has created potent new storm slabs at higher elevations. Watch for increased reactivity in wind-exposed terrain. At lower elevations where rain has fallen, destructive wet slabs are also possible.
Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Persistent Slabs

About 100cm of recent storm snow overlies weak crystals which formed in early January. In recent days, very large avalanches were observed on these layers, and human triggering remains a very real concern.
The new snow will require several days to settle and stabilize.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 3 - 6

Loose Wet

The snowpack is saturated at elevations where rain has fallen. Pushy loose wet avalanches are a concern in steep terrain.
Be cautious of wet sluffing in steep terrain.>Even small avalanches may run a long ways under the current conditions.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3