North Columbia

Avoid wind loaded features especially near ridgelines, and watch for strong sunshine affecting south facing slopes - reactivity may increase if skies clear.

Deep persistent weak layers continue to be a concern in this region, avoid thin and rocky areas and check out the latest Forecasters' Blog.

Human and naturally triggered slab avalanches were mostly reported to size 2 throughout the region on Thursday, isolated size 3 avalanches were reported from heavily wind loaded features.

Avalanche activity has been consistent throughout the week, as storm totals rose. This included storm slabs, wind slabs in wind loaded features and loose dry avalanches from steep sheltered terrain.

Most avalanches involved the storm snow or ran on the old snow surface. Some activity occurred on the buried facets and surface hoar layers.

Deep persistent slab avalanche reports continue to trickle in over the week. In Glacier National Park a size 2.5 occurred on Monday, and a size 3 occurred in the northwest Purcells on Wednesday triggered by a cornice fall. Large human triggered deep persistent slab avalanche activity continues to occur in the east Purcells, including a fatal size 3 avalanche near Invermere on Wednesday, which is directly adjacent to this forecast region.

These avalanches have been occurring on all aspects and generally between 2200 m and 2800 m in elevation. They are evidence that the low probability but very high consequence weak basal snowpack is still triggerable. Riders should continue to avoid thin and rocky snowpack areas, which are often found near ridgelines or below headwalls.

Storm totals have reached 40-70 cm for most of the central Columbias. Recent winds have redistributed this into deeper deposits on north and east facing aspects. This storm snow sits over wind effected surfaces, a thin sun crust on steep south facing slopes.

Below this interface, around 50-90 cm deep, a layer of small surface hoar from exists in lower elevation sheltered areas and more widespread faceted (sugary) snow and heavy wind effect from the late February Arctic blast. Reports suggest this interface is beginning to bond and strengthen.

Another small layer of surface hoar is buried 70-130 cm deep, from mid February. This layer is most likely found around treeline elevations in areas sheltered from the wind. The remainder of the mid-snowpack is generally strong.

A layer of large and weak facets that formed in November is deeply buried. Found near the base of the snowpack it is very slow to gain strength. The likelihood of human triggering this layer is currently low given its depth. However deep persistent slab avalanches continue to be reported in the interior, confirming it is still best to avoid steep, thin, rocky slopes at alpine and upper treeline elevations.

Friday Night

Cloudy with light snowfall easing overnight, up to 5 cm for the South Columbia's and trace amounts for the north. Light southeast winds. Freezing levels below valley bottom.

Saturday

A mix of sun and cloud. Light to moderate east winds. Freezing levels around 500 m in the north and rising to 1000 m in the far south, alpine high of -5 °C. Possible flurries.

Sunday

Mostly sunny with cloudy periods. Light to moderate east winds. Freezing levels below 500 m, alpine high of -8 °C.

Monday

Mostly cloudy. Light to moderate southerly winds. Freezing levels around 800 m, alpine high of -7°C. Light snowfall possible.

More details can be found in the Mountain Weather Forecast.

• Continue to make conservative terrain choices while the storm snow settles and stabilizes.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Minimize exposure to sun-exposed slopes when the solar radiation is strong.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.