Archived

Avalanche Forecast

Apr 21st, 2018–Apr 22nd, 2018

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

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: Sea To Sky.

Warming and solar radiation will drive the avalanche danger in the coming days. Watch for conditions that change throughout the day, and be cautious of overhead hazards.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A ridge of high pressure will develop for the forecast period bringing clear skies and light ridgetop winds. The freezing level will hover around 1800m on Sunday and then rise to about 2600m for Monday and Tuesday.

Avalanche Summary

No new avalanches were reported at the time of publishing this bulletin, although I'm sure there was a round of wind slab activity on Saturday in response to new snow and strong overnight winds. Loose wet avalanches and cornice falls are expected to become problematic with warming and solar radiation forecast for Sunday and Monday. Warming also has the potential to wake-up the late March crust interface with the possibility of surprisingly large and destructive avalanches.

Snowpack Summary

New snow and wind on Saturday formed fresh wind slabs in upper elevation lee terrain. The new snow overlies settled storm snow on shaded aspects above 2000m and a melt-freeze crust in most other areas.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 140 cm below the surface. This layer is spotty in its distribution and has recently produced large and destructive avalanches. It is most likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. Professionals are treating this layer very cautiously and avoiding steep, unsupported terrain. Read Conditions report here.The mid and lower snowpack are well-settled and strong.

Avalanche Problems

Loose Wet

Warming and solar radiation are expected to trigger loose wet avalanches, especially in steep, sun-exposed terrain. Loose wet avalanches can be pushy and entrain mass quickly. Warming may also trigger destructive cornice failures.

Use caution above cliffs and terrain traps where small avalanches may have severe consequences.Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 2.5

Persistent Slabs

Professionals are traveling cautiously in shaded upper treeline and alpine terrain due to a weak layer buried 60 to 140 cm below the surface. Forecast warming and cornice failures will likely re-activate this destructive interface in isolated terrain

Be aware of the potential for wide propagation due to the presence of buried weak layers.Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3.5

Wind Slabs

New snow and strong winds from Friday night have formed new wind slabs in upper elevation lee terrain. Although they're likely to gain strength quickly, I'd remain cautious around ridge crests and in gullies.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2