Avalanche Forecast
Regions: Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Jasper, 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.
Avalanche Problems
Wind Slabs
Additional precipitation with strong SW winds will rapidly build new and add to our wind slab problem on lee and cross-loaded features. New snow could settle into storm slabs on southerly aspects depending on localized snowfall amounts and winds.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely - Very Likely
Expected Size: 1 - 2.5
Loose Wet
Weak overnight freezes, warm temperatures, and some rain / wet snow will keep this problem at the top of our list at tree line and below. Wet loose avalanches will likely step-down to our basal facets in steep terrain resulting in large avalanches
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Likely - Very Likely
Expected Size: 1 - 2.5
Deep Persistent Slabs
The bottom of the snowpack is inherently weak with well-developed Facets and Depth Hoar. Storm /Wind slabs or wet loose avalanches could trigger the deep persistent slab resulting in large avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible - Likely
Expected Size: 2 - 3.5