Avalanche Forecast
Regions: Banff, Banff Yoho Kootenay, East Side 93N, Field, Kootenay, LLSA, Lake Louise, Sunshine, West Side 93N.
Cooler, cloudy weather with light precipitation is expected on Sunday. Freezing levels will rise to around treeline.
Avalanche hazard will be lower in the morning, and will depend on the quality of the overnight refreeze and the amount of daytime warming. Start and finish early.
Click the link for more info on spring conditions.
Confidence
High
Avalanche Summary
Solar heating contributed to increased loose wet avalanche activity on E-S-W aspects on Saturday, beginning on steep solar aspects by noon. By mid afternoon, we were seeing the crust break down which resulted in a loose wet avalanche cycle to size 2.
We also received reports of recent cornice releases in the afternoon over the past couple of days.
Snowpack Summary
Surface crusts exist to ridgetops in the morning on solar aspects, and on all aspects at treeline and below. The top 10-20 cm of snow on solar aspects was getting moist by noon on Saturday.
North alpine slopes hold 5-15 cm of dry snow over firm surfaces. The March 27 crust is 30-70 cm deep and extends to about 2500 m on North slopes, reaching the ridgetop on solar aspects.
Below the settled mid-pack, weak facets and depth hoar remain.
Weather Summary
On Sunday, cloud cover will increase, accompanied by light precipitation as a low-pressure system moves into the forecast region. Treeline temperatures will be between -1°C and +3°C with light SW winds.
Terrain and Travel Advice
- A moist or wet snow surface, pinwheeling, and natural avalanches are all indicators of a weakening snowpack.
- Start your day early and be out of avalanche terrain during the heat of the day.
Avalanche Problems
Loose Wet
Monitor the overnight crust refreeze, daytime temperatures and solar inputs. The likelihood of loose wet avalanches will increase with warmer temperatures as the day progresses. Start and finish your tour early to avoid this problem.
Aspects: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
An 80 cm thick midpack slab sits over a weaker, facetted base. On most slopes, recent sun crusts and a buried March 27 rain crust cap this slab, adding strength as long as it is frozen. We suspect it would take a large trigger, like a cornice or intense solar input, to trigger these deeper layers.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3