Archived

Avalanche Forecast

Jan 30th, 2015–Jan 31st, 2015

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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

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

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Sun and solar radiation may have a significant destabilizing effect on the snowpack. As freezing levels rise throughout Saturday, so will the Avalanche Danger.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Friday's storm system will dissipate on Saturday as a weak ridge develops. On Sunday and Monday, the ridge will flatten-out allowing for a series of pacific system to impact the region. Saturday: Generally clear skies with valley fog / Light northwest winds / Freezing level at 1600m Sunday: Up to 15cm of new snow / Moderate southwest winds / Freezing level at 400m Overnight Sunday and Monday: Up to 25cm of new snow / Moderate southwest winds / Freezing level at valley bottom

Avalanche Summary

At the time of publishing this bulletin, there was no new avalanche activity reported from the field. That said, I'm sure there was a healthy round of storm slab activity in response to heavy snow accumulations on Friday. Looking forward, I'd remain cautious of recently formed storm slabs, as they may remain sensitive to human triggering, especially in wind-exposed terrain. Additionally, persistent weak layers should remain on your radar as they may become reactive with the loading of the new snow, or with warming and solar radiation forecast for Saturday. Any avalanche on these deeper persistent weaknesses would be destructive in nature.

Snowpack Summary

Moderate to heavy snowfall (with rain at lower elevations) and strong southwest winds have likely built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. A rain crust and/or surface hoar layer buried mid-January can be found about 100cm below the surface, the depth varying greatly depending on whether the slope is wind-loaded or wind-scoured. The structure of this layer may have strengthened somewhat. Still, I would recommend giving this layer a little more time to bond before discounting it from the avalanche equation. The November crust/ facet combo near the bottom of the snowpack is thought to be generally well bonded. However, this deep and destructive layer is still reported to be reactive in the far north of the region.

Avalanche Problems

Storm Slabs

Storm accumulations from Friday will likely remain sensitive to human triggering. Expect increased reactivity in wind-exposed terrain. A smaller surface avalanche in motion may also trigger a larger avalanche on deeper layers.

Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Minimize exposure to sun exposed slopes when the solar radiation is strong.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Loose Wet

Watch for pushy loose wet avalanches in steep, sun-exposed terrain on Saturday. Loose wet avalanches have the potential to "step-down" to deeper, more destructive layers.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Be cautious of wet sluffing in steep terrain.>Avoid traveling on ledges and cliffs where small avalanches may have severe consequences.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

Although less likely to trigger, persistent weak layers are still capable of producing large and destructive avalanches in isolated terrain. Possible triggers include a cornice fall or intense solar radiation.

Be aware of the potential for large, deep avalanches due to the presence of buried crusts and/or 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: Possible

Expected Size: 3 - 6