Archived

Avalanche Forecast

Apr 11th, 2014–Apr 12th, 2014

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Coast.

Avalanche danger can rise very quickly with warming and solar radiation. Be aware of changing conditions and overhead hazards. Terrain choices and timing can be critical.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Overview: A ridge of high pressure will dominate the coast by Saturday morning bringing mainly sunny skies and rising freezing levels for the forecast period.Saturday: Mostly clear skies / Moderate northerly winds / Freezing level at about 1600mSunday: Clear skies / Light northerly winds / Freezing level at about 1700mMonday: Mostly clear skies with increased cloud late in the day / Light southwest winds / Freezing level rising to about 2600m

Avalanche Summary

Cornices have started to fail up to size 2.5 with warmer temperatures and sunny skies. Of the cornice fall observed, none triggered deeper slabs on the slopes below. Numerous loose wet avalanches occurred up to size 2 on steeper solar aspects, and are expected to continue with forecast warming. Also, in recent days a very large (unknown size) persistent slab avalanche was observed on the northwest face of Mt Matier. The trigger is unknown; however, it demonstrates the potential for destructive persistent slab avalanches. See Wayne Flann's Avalanche Blog for a photo.

Snowpack Summary

Up to 20 cm of recent snow sits above a solid melt freeze crust. The new snow seems to be bonding with help from the warmer temperatures; however, isolated wind slabs may still exist. Surface snow is seeing daily a melt-freeze cycle on all aspects below 2000m, and to mountain top on southerly aspects.Surface hoar growth has been noted on shady slopes at higher elevations, and large sagging cornices are becoming weak with daytime warming.A couple persistent weak layers exist deeper in the snowpack. The early March crust layer is down 60 - 100cm and the February crust/facet layer is now deeply buried down 150 250 cm. These layers are mostly inactive at this time, but could re-awaken with extended warming, solar influence and large triggers like cornice fall.

Avalanche Problems

Loose Wet

Watch for loose wet avalanches with daytime warming on steep, sun-exposed slopes. Loose wet avalanches can be pushy and entrain mass quickly.

Avoid slopes when temperatures rise and the surface snow becomes moist or wet. Signs of instability are pinwheels and natural avalanches. >Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Cornices

With forecast warming and intense solar radiation the likelihood of triggering a large cornice fall will increase dramatically. A cornice fall may also be what it takes to "wake-up" deep and destructive weaknesses which formed earlier in the season.

Extra caution needed around cornices with current conditions.>Cornices become weak with daytime heating. >

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 4

Deep Persistent Slabs

Although unlikely, deep persistent avalanches would be very large and highly destructive. Possible triggers include cornice fall, a surface avalanche in motion, warming and intense solar radiation.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Large triggers like cornice fall could initiate a deep persistent slab.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 3 - 6