Avalanche Forecast

Archived

Mar 1st, 2022–Mar 2nd, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

North Columbia.

Triggering storm slab avalanches is a concern in steep terrain as the new snow needs more time to strengthen.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

TUESDAY NIGHT: Cloudy with isolated flurries bringing up to 5 cm of snow, moderate wind from the southwest, treeline temperatures drop to -5 C.

WEDNESDAY: Mostly cloudy skies with some convective flurries bringing localized accumulations of 5-10 cm, light wind from the south with moderate gusts during flurries, treeline temperatures reach -2 C with freezing level reaching 1500 m.

THURSDAY: Mostly cloudy with isolated flurries bringing up to 5 cm of snow, light wind from the northeast, treeline temperatures around -5 C.

FRIDAY: Mostly sunny, light wind from the northeast, treeline temperatures around -8 C.

Avalanche Summary

Storm slabs were reactive on Monday with numerous small (size 1) human triggered avalanches at treeline elevations and a few reports of larger (size 2) natural avalanches in the alpine. These avalanches occurred in the top 20 to 30 cm of new snow. We suspect storm slabs were also touchy on Tuesday, but will gradually stabilize over the coming days.

The last report of a persistent slab avalanche was on Feb 20, which was a size 2.5 avalanche triggered by a cornice. While persistent slab activity has declined, we are uncertain about how persistent weak layers will react to warming and the weight of the recent snow.

Snowpack Summary

Recent storm snow has likely settled into 20 to 30 cm of heavy powder at upper elevations and wet/crusty snow below 2000 m. Reactive slabs remain possible on wind loaded slopes and perhaps some isolated areas where this snow sits above sun crusts or feathery surface hoar. Two potential weak layers exist within the upper snowpack: the mid-February layer (down 40 to 60 cm) and the late-January layer (down 100 cm). They both consist of surface hoar and/or melt-freeze crusts. The reactivity of these layers has declined over the past week.

Terrain and Travel

Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
Choose slopes that are well supported and have limited consequence.
Stay off recently wind loaded slopes until they have had a chance to stabilize.
Caution around convexities or sharp changes in terrain.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.