Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
Solar heating has already exerted significant impacts on the snowpack this week. A bigger punch is forecast to arrive Saturday which may have the biggest effect yet.
While the dry snow on higher, north slopes will draw travelers this weekend, be warned that this is also where the risk of triggering the persistent slab is the greatest.
Confidence
Moderate
Avalanche Summary
Lake Louise avalanche control triggered a size 2 deep persistent slab with explosives in a piece of north-facing terrain above Lipalian 3 just above treeline Thursday.
Snowpack Summary
Surface crusts on solar aspects up to ~2800 m. Up to 30 cm of dry snow on north slopes at higher elevations. On southerly aspects, this 30cm contains several crusts.
Below this, a prominent rain crust (Mar 27) is found everywhere up to at least 2300m. The strength and extent of this crust varies area to area.
Below this, a 70 cm slab of dense snow overlies another 70 cm of weak facets. This is the main problem in the snowpack and is of particular concern when the crusts above it are weak
Weather Summary
Solar heating is the most important input right now.
A ridge brings light to moderate west winds under clear skies through Sunday night.
Overnight lows Friday night near treeline will be near -10C with the freezing level climbing to near 2500m Saturday afternoon.
While the winds may be enough to discourage the effects of solar inputs in higher, open areas, expect moist snow on sheltered steep slopes
Terrain and Travel Advice
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
- Avoid steep, sun-exposed slopes when the air temperature is warm or when solar radiation is strong.
- Start your day early and be out of avalanche terrain during the heat of the day.
- Avalanche danger will increase as the surface crust breaks down.
Avalanche Problems
Persistent Slabs
Below the recent snow, a 50-90 cm slab sits on the weak lower snowpack. On all but high north aspects, recent sun crusts and the March 27 rain crust cap this slab, providing some security. Use extreme caution in higher, thinner areas or when these superficial crusts are weak or are breaking down.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1.5 - 3
Loose Wet
While there are crusts almost everywhere on solar aspects, solar inputs will still affect steep and / or rocky areas. As heating develops, higher and partially shaded slopes will be affected as well. Sluffing off of steep rocky faces should be expected and cornice failures are more likely
Aspects: North East, East, South East, South, South West, West, North West.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 2