An avalanche cycle is underway, evidenced by today's avalanche control results and observations of natural avalanches. Avalanche control is planned for Thursday, February 9 on Hwy 93S (Mt Whymper, Vermillion Peak & Simpson) so no access to these areas on Thursday. We expect this current peak in avalanche danger to last for a few days while the snowpack adjusts. Human triggering is likely avalanche starting zones.
Sustained SW 40 km/hr winds with gusts to 75 km/hr over the past 48 hours have moved significant amounts of new snow into leewards and cross-loaded areas. These slabs are sensitive and can be easily triggered by humans. Natural activity may subside over the next few days but remain very careful for human-triggered windslabs.
The recent new snow and wind have added enough load to reawaken the deep persistent slab problem and we have observed several avalanches failing on the ground facets. Step back for a few days while the snowpack adjusts to this new load as we are likely to still see some unusual or large avalanches for the next few days.
Lots of avalanches were observed today, both natural and explosive triggered. Field teams observed widespread activity up to size 3 on the Icefields Parkway with propagations up to 300 meters. Avalanche control on the Sunshine road produced excellent results up to size 3 and the Emerald Lake Slide path has a size 2 near the summit.
Regional snowfall totals since Feb 1: Bow Summit 43 cm, Bosworth 37 cm, Sunshine 34 cm, Simpson 31 cm, Stanley 22 cm.
Strong winds have moved this new snow into widespread, reactive windslabs at higher elevations, confirmed by today's avalanche control. Two crusts are buried within the upper snowpack and the November facets remain near the base. These buried weak layers are now producing avalanches, including a wake-up of the November facets. Minimal reactivity has been observed below treeline.
After a short clearing on Wednesday, another system crosses the area starting Thursday afternoon and evening. This next system brings only 5 cm of snow, but with 50-60 km/hr winds and temperatures remaining in the -5 to -10 range for alpine areas. Longer term, the systems keep coming, but no significant snowfall amounts are predicted for the next week.
More details can be found in the Mountain Weather Forecast.
