Archived

Avalanche Forecast

Mar 18th, 2016–Mar 19th, 2016

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

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 Inland.

Lurking persistent weaknesses and mild spring-like weather make me reluctant to drop avalanche danger any lower. Continue to approach large alpine slopes with caution, especially with cornices perched above.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SATURDAY: Increasing cloud. The freezing level is around 1100-1300 m. Winds should be moderate from the SW-SE. SUNDAY: Cloudy with a chance of flurries. The freezing level is near 1200 m and winds are light to moderate from the southeast. MONDAY: Cloudy with light snow. The freezing level is around 1200 m and winds are light from the east.

Avalanche Summary

On Thursday there were reports of loose wet sluffs up to size 1.5 on solar aspects in the afternoon. A larger loose wet cycle with wind slab activity (to size 2.5) was observed in the previous 24 hours. In the far north of the region, natural cornice falls continue to trigger size 2-3.5 persistent slab avalanches, primarily on north-facing alpine slopes.

Snowpack Summary

In sheltered areas at higher elevations, 20-30cm of low density facetting snow can be found. Recent southerly winds have redistributed the surface snow in exposed terrain formed wind slabs and cornices in leeward terrain. South facing slopes could be capped a sun crust or moist snow depending on the time of day. A layer of surface hoar from early March can be found down 60-80cm but only seems to be a problem for the northern half of the region. Professional operators are still tracking two deep weak layers from early-January and early-February which can be found down about 1m or more. These layers have been dormant for a couple weeks but could wake up with heavy storm loading, substantial warming, or a heavy trigger like a cornice fall. In the far north of the region, there is an isolated weakness at the base of the snowpack that has been responsible for some very large and destructive avalanches.

Avalanche Problems

Wind Slabs

Wind slabs may still be lurking on a variety of aspects in exposed terrain. Also, watch for pockets of wind slab in cross-loaded gullies.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

Cornices

Mild temperatures and periods of sunshine could weaken large overhanging cornices causing them to fail naturally.

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: 2 - 5

Deep Persistent Slabs

Three buried weaknesses remain a concern, mainly in the north of the region (see snowpack discussion for details). Isolated very large avalanches remain a possibility, especially with a heavy trigger like a falling cornice.

Be aware of thin areas that may propagate to deeper instabilites. >Be aware of the potential for full depth avalanches due to deeply buried weak layers. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6