Sunny and warm for Thursday, which will produce a daily melt-freeze cycle. Avalanche danger ratings reflect the highest danger for the day. The snowpack in Banff, Yoho and Kootenay remains weak, despite the onset of spring, and we remain suspicious of all steep alpine terrain on shaded aspects where no crusts exist.
5-10 cm from Tuesday night with WSW wind has formed thin windslabs on alpine lee features reactive to ski cuts by ski hill snow safety teams.
A slab up to 80 cm thick 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.
Thursday looks like a sunny day, which will inevitably cause loose wet avalanches to release. Be wary in gullies or near rock bands which absorb the heat.
The local ski areas continue to mitigate size 1 windslabs and small cornice buildup in leeward, alpine areas and on Tuesday, HWY 93 road patrol, one size 2 recent cornice failure on Crowfoot mountain, scrubbing to the ground in extreme terrain.
Surface crusts are found in most locations except north-facing alpine zones. The integrity of the snowpack is based mostly upon the strength of the surface crust when it refreezes overnight (or doesn't). In areas with no surface crust, concern remains due to the weak basal facets, which have plagued the mid and base of the snowpack all winter. This makes most steep, alpine terrain in the shallow snowpack areas of BYK suspect, and we have low confidence in this snowpack.
Wednesday evening looks clear, giving a good possibility of a freeze for Thursday morning.
Thursday and Friday look like sunny days, with valley bottom highs of +10 and freezing levels reaching 2500 m on Thursday. Slow cooling will follow into the weekend, with classic spring weather - mostly clear but some rain and snow flurries but no significant accumulation (~5 cm).
