Warm temperatures are expected to persist into Monday, limiting the overnight refreeze of the upper snowpack. Monitor local conditions and minimize exposure to bigger terrain until things cool off.
Areas east of HWY 93N and the Lake Louise backcountry have a thinner snowpack, making it more susceptible to human-triggering.
Below the recent snow a 30-80 cm slab sits on the weak facetted lower snowpack. On all but high north aspects, recent sun crusts and the March 27 rain crust cap this slab providing some security. Use caution in higher, thin snowpack areas or where these crusts are weak or breaking down with heating.
As the surface crusts break down and temps stay warm, wet slabs, sluffing off of steep faces, and triggering deeper instabilites becomes more likely. Monitor local conditions for the overnight refreeze and minimize exposure to steep terrain if the surface snow does not freeze well on Monday.
Solar-triggered natural avalanches up to size 2 were occurring in steep terrain as the day heated up on Sat/Sun, occasionally gouging down into the lower snowpack.
A natural size 2.5 slab avalanche occurred Saturday in the early afternoon on a steep south aspect of Mt Jimmy Simpson. It was likely triggered by a sluff and failed on the January facets.
Several cornice failures have also been observed later in the day, occasionally triggering slabs up to size 2.
Light wind effect in the alpine. On alpine north aspects, 15-30 cm of dry settled snow sits over the Mar 27 crust that exists to ~2500 m. On solar aspects sun crusts are present to ridgetop with moist snow later in the day. A supportive surface crust exists in most places below treeline.
A 30-70 cm firm midpack overlies the weak January facets and basal depth hoar which remain a concern.
Treeline snowpack depths range from 100 to 150 cm.
Air temps and solar inputs are key things to pay attention to as we move into spring.
Sunday night: Becoming cloudy. Alpine temps remain near 0°C with minimal refreeze overnight. Ridge wind light to 25 km/h. Freezing level staying around 2400 m.
Monday: Mainly cloudy with light precip beginning in the late afternoon. SW winds in the moderate range. Treeline temps near +2°C with freezing levels staying around 2400 m.
