Avalanche Forecast

Archived

Mar 20th, 2023–Mar 21st, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Jasper, Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Maligne, Marmot, Miette Lake, Pyramid.

The region is trending towards spring like conditions. Start early and finish early as solar warming is having the strongest effect typically by mid-afternoon.

Wet loose avalanche activity on solar aspects has been consistently triggering the deep persistent layer at all elevations this week.

Ice climbers should choose objectives with no overhead hazard and minimal sun exposure.

Confidence

Moderate

Avalanche Summary

Several wet loose avalanches observed on Monday occurring mid to late afternoon on Sunday - all elevations southerly aspects with many stepping down to the basal weakness or triggering persistent and deep persistent slab avalanches. One size 3 deep persistent slab on Sunset peak southwest aspect propagated across half of a large alpine bowl feature. Afternoon loose wet cycle continues in the Coleman area 93N just south of Weeping Wall with avalanches reaching the ditch and some spilling onto the highway.

Don't forget to post avalanche observations to the MIN.

Snowpack Summary

Sun crust on solar aspects at all elevations breaking down by early to mid afternoon. Moderate SW winds after March 13th created pockets of wind slab on lee aspects. Approximately 20-30cm down is a buried sun crust at low elevations on steep southerly slopes and a surface facet layer in sheltered terrain. The mid-pack is 40 to 80cm of supportive facetted snow. Near the ground it is generally weak with large facets and depth hoar.

Weather Summary

A ridge of high pressure will remain the dominant weather feature through late Thursday. Tuesday will be clear skies, light northerly winds with the freezing level rising to 2000m. Desent recovery overnight with a low of -12C. Similar conditions on Wednesday with winds changing to westerly and a freezing level up to 2100m. Late Thursday the ridge will give way to a more active pattern with light precipitation forecast for Friday.

Detailed weather forecasts from Avalanche Canada: https://avalanche.ca/weather/forecast

Terrain and Travel Advice

Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Be alert to conditions that change with elevation and sun exposure.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.