Avalanche Forecast
Issued: Mar 15th, 2021 4:00PM
The alpine rating is Storm Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeUp to 20 cm new snow by the end of the day and strong to extreme southwest wind will form touchy wind slabs. The snowpack needs time to stabilize after the big weekend storm. Stay vigilant and watch for signs of instability like whumpfing, hollow sounds and shooting cracks.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
MONDAY NIGHT: Cloudy, 5 to 10 cm new snow, 70 km/h southwest wind, alpine low -3 C, freezing level rising to 700 m.
TUESDAY: Cloudy, 5 to 10 cm new snow, 60 km/h southwest wind, alpine high 0 C, freezing level 1000 m.
WEDNESDAY: Mostly cloudy, 10 to 15 cm new snow, 50 km/h southerly wind, alpine high 0 C, freezing level 900 m.
THURSDAY: Mostly cloudy, 5 to 10 cm new snow, 30 km/h southerly wind, alpine high 1 C, freezing level 1000 m.
Avalanche Summary
A widespread natural avalanche cycle with storm slab avalanches up to size 4 started on Friday morning and went on for the entire weekend. Most natural avalanche activity was observed on solar aspects within the storm snow. On polar aspects avalanches most likely ran on the surface hoar layer which formed last week before the storm hit the region. Explosives triggered storm slab and wind slab avalanches of size 2 to 3 in the entire region. A natural persistent slab avalanche of size 3.5 was observed east of Kitimat. In other parts of the region the persistent weak layer seemed to be unreactive. Numerous wet slab avalanches up to size 3 and wet loose avalanches of size 1 to 2 were observed as well as several glide snow avalanches up to size 2.5. On Sunday skiers triggered avalanches of size 2 at treeline on southwest and northwest aspects.Â
Several natural glide snow avalanches and loose wet avalanches up to size 2 were reported on Wednesday. Some avalanche activity was observed on southerly aspects on Tuesday during the heat of the day. A few cornices were also triggered, which did not trigger slabs on the slopes below.
Snowpack Summary
The recent storm brought up to 150 cm snow in the south of the region and about 50 cm in the north. The precipitation was combined with moderate to strong southerly wind and fell as rain below 900 m saturating the upper snowpack. The new snow may overly feathery surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects and below treeline.
Around 100 to 300 cm overlies a persistent weak layer buried in mid-February that may still be a concern in isolated parts of the region. The layer consists of feathery surface hoar crystals in areas sheltered from the wind and sugary faceted grains that formed during February's cold snap. Avalanche activity on this layer has mostly occurred west of Terrace along Highway 16 and in the Kitimat area in the past weeks.
There are currently no layers of concern in the mid and lower snowpack.
Terrain and Travel
- Start with conservative lines and watch for clues of instability.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Storm Slabs
The recent storm brought up to 150 cm snow in the southern half of the region and about 50 cm in the north. The precipitation fell as rain below 900 m and saturated the upper snowpack. The storm snow will stay reactive while it settles, especially where it sits on surface hoar on northerly aspects and in sheltered terrain features around treeline or a melt-freeze crust on southerly aspects. Skiers and riders might be able to trigger avalanches, especially on convex rolls and unsupported slopes.
Strong to extreme southwest wind will form touchy wind slabs in the alpine and at treeline where loose snow is available for transport. These slabs may be found farther down on lee slopes than expected. During the storm moderate to strong southerly wind has formed reactive wind slabs in lee terrain features. Triggered wind slabs may step down and release the entire storm snow.
The wind will contribute to cornice growth and the additional load might lead to cornice failures.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 16th, 2021 4:00PM