Extensive avalanche control is planned in the Yoho and Highway 93 North areas on Wednesday, March 23.
Last week's slabs are 30-50cm thick but are likely to only be reactive in steep features. Sunday's new slabs are thin, soft and isolated to immediate lees but will be sensitive. Expect all of these slabs to become more reactive with warming.
Buried crust/facet layers exist in the upper snowpack on solar aspects and all aspects below 1800m. As the slabs overlying all of these crusts becomes heated, they will become much more sensitive to triggering. Wet slab activity may become possible.
As freezing levels rise, expect loose wet sluffs to become active first in lower elevation steep terrain, then progress higher. Depending on cloud cover and solar inputs, this may be intensified on steep solar slopes and solar cliffy terrain.
Wednesday will be mainly cloudy with isolated flurries and moderate winds out of the west, freezing levels could reach as high as 2500m. A cold front will arrive in the area on Wednesday evening, freezing levels will lower back to valley bottom. Thursday will be a mix of sun and cloud with alpine temps up to -6.
5-10cm of recent snow overlies old wind slabs in alpine and isolated areas at treeline. The recent snow has formed new soft wind slabs in lee alpine features. Surface snow is moist on sheltered solar aspects at all elevations, and below 1700m on all aspects. Several buried crusts exist on solar aspects and are found 30 to 80 cm deep.
Natural cornice releases up to size 2.5 on all aspects and a skier triggered size 2 wind slab on an east aspect were reported on Monday. On Sunday, Bourgeau-Left waterfall (next to Sunshine gondola) released a large natural avalanche that ran over the waterfall and hit Healy Creek. This may have been triggered by a cornice or strong solar effect.
