Archived

Avalanche Forecast

Mar 16th, 2016–Mar 17th, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

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

2: Moderate

The avalanche danger rating at treeline will be moderate

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

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

Strong sunshine will increase avalanche danger during the day. Plan your route to minimize exposure to big sun-drenched slopes in the afternoon.

Confidence

High

Weather Forecast

THURSDAY: A mix of sun and cloud. The freezing level is around 1000-1200 m. Ridge winds are light to moderate from the E-SE. FRIDAY: A mix of sun and cloud. The freezing level should jump to around 1700-1900 m and ridge winds are moderate from the E-SE. SATURDAY: Increasing cloud with a chance of flurries. The freezing level is around 1300 m and winds should be light.

Avalanche Summary

Recent avalanche activity has mainly involved natural and explosive-triggered cornice falls. In the far north of the region, a natural cornice release triggered a size 2.5 persistent slab avalanche on the early March surface hoar layer on Monday, and a size 2 cornice triggered persistent slab was also observed on Tuesday. Cornices and lingering slabs may become weak, and could even fail naturally during periods of strong sunshine. Loose wet sluffing is also expected from steep sun exposed slopes.

Snowpack Summary

20-30cm of new snow has accumulated over the last couple days in sheltered areas. Strong southerly winds have redistributed the surface snow forming wind slabs and adding mass to cornices. On south aspects, the recent storm snow may have buried a sun crust. Lower elevations are going through daily melt-freeze cycles. A layer of surface hoar or melt-freeze crust buried on March 3 is down 70-100cm and has been recently reactive in the areas north of Stewart. An older crust/facet layer buried in early February can now be found down over a meter but this layer has been dormant for several weeks.

Avalanche Problems

Wind Slabs

We could some reverse loading and fresh wind slab formation from moderate East-Northeast winds on Thursday. Loose wet sluffing is also likely on steep sunny slopes.

Be cautious as you transition into wind affected terrain. >Minimize exposure to sun exposed slopes when the solar radiation is strong. >

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Cornices

Cornices are reported to be large and weak. Natural cornice releases are possible with sun exposure and warming.

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

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 5

Persistent Slabs

A layer of buried surface hoar, down 70-100 cm, has recently been reactive around Stewart and north. An old weak crust layer down over 1m remains an isolated concern in the south of the region.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >Dig down to find and test weak layers before committing to a big slope. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6