Archived

Avalanche Forecast

Feb 15th, 2019–Feb 16th, 2019

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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: South Columbia.

There is uncertainty about how much precipitation will fall, particularly in the south of this region. If there is more than 15 cm, treeline and below treeline areas will go to considerable.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY NIGHT: Around 5 cm of low density snow expected. Mostly light winds.SATURDAY: 4-8 cm new snow. Treeline temperatures around -6C. Light northeasterly winds.SUNDAY: 2-4 cm new snow. Treeline temperatures around -8C. Light northeasterly winds.MONDAY: Flurries, with some clear spells. Treeline temperatures around -10C. Moderate northwesterly winds.

Avalanche Summary

Numerous size 1-2 wind slab, storm slab and persistent slab avalanches were reported from areas in the south of the region on Tuesday, Wednesday and Thursday. These were predominantly at treeline and in the alpine on all aspects. In the the north part of the region avalanche activity on Thursday was primarily reported as wind slabs to size 1.5, again on a variety of aspects in the alpine and at treeline.

Snowpack Summary

Relatively light amounts of low density snow have been accumulating above old surfaces that include previously wind-affected slopes, sugary facets and/or feathery surface hoar. In the south of the region, amounts since Tuesday are approximately 35 cm, while in the north, amount are more like 15 cm. Strong northeast winds have blown this snow into wind slabs onto unusual south- to west-facing slopes. The wind slab is reported to be very touchy, since it lies directly over this upper weak layer.Lower down in the snowpack there are two additional weak layers of surface hoar, which have produced large avalanches in the region. A layer buried at the end of January is around 40 cm deep and a layer buried mid-January is between 50 and 90 cm deep. The mid-January layer may also be associated with a melt-freeze crust on southerly aspects. These layers are most prominent at treeline and below.The remainder of the snowpack is generally well-settled. However, there have been sporadic reports of very large avalanches that have released near the base of the snowpack. Most of the avalanches have been in the high alpine. There has been about one report a week for the past month.

Avalanche Problems

Wind Slabs

Northeasterly winds have set up touchy wind slabs on unusual southerly and westerly aspects. Older buried wind slabs on other aspects may still be reactive.

Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2

Persistent Slabs

Two weak layers of surface hoar crystals are buried between 30 and 90 cm in the snowpack. The layers are most prominent at treeline and below.

Be aware of the potential for wide propagation.Avoid steep, open and/or sparsely treed slopes at and below treeline.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1.5 - 2.5