Avalanche Forecast

Archived

Apr 10th, 2023–Apr 11th, 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 unlikely, human triggered possible.

Regions

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

The storm pulse on Sunday produced less than forecasted precipitation. An additional 15-25mm is expected Tuesday through Wednesday with increasing southwesterly winds mid day Tuesday. Increased wind slab avalanche activity is expected in the alpine and exposed tree line over the next couple of days. Travel below 1800m will likely remain heinous until we receive a good overnight freeze.

Confidence

Moderate

Avalanche Summary

Explosive control Sunday on a large road side cut bank at 1800m produced several wet loose avalanches up to size 2.5 - isothermal running on the basal facets. One size 2 from a northeast alpine feature on Mt Saskatchewan also observed - suspect wind slab.

Patrol on 93 Monday observed 3 size 2 wind slabs variable aspects in the alpine showing descent propagation.

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

Snowpack Summary

Up to 7mm precipitation from Sunday's storm pulse fell as mixed snow/rain below 2000m. Snow in the alpine was accompanied by strong southwest winds creating new wind slab lee and cross loaded features. Snowpack below 1800m is in a diurnal isothermal freeze thaw. The mid pack above this elevation consists of multiple layers of dense wind effected snow in open areas, sun crusts on solar aspects, and facets. Depth hoar and basal facets make up the base of the snowpack.

Weather Summary

A stalling low pressure system will bring continued light to moderate precipitation Tuesday and Wednesday - models vary showing 15-25mm possible. Freezing level will rise to 1900m Tuesday, valley bottom overnight and 1600m on Wednesday. Rain is possible at lower elevations. SW winds will increase to moderate values Tuesday pm.

Terrain and Travel Advice

Minimize exposure during periods of heavy loading from new snow, wind or rain.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.

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.