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RegisterDec 27th, 2019–Dec 28th, 2019
South Rockies.
Triggering large deep persistent slab avalanches remains a concern. Travel with caution and avoid steep rocky terrain.
FRIDAY NIGHT: Clear with cloudy periods, 30-50 km/h wind from the northwest, alpine temperatures drop to -15 C.
SATURDAY: Mix of sun and cloud, 30 km/h wind from the west, alpine high temperatures around -10 C.
SUNDAY: Cloudy with some light flurries and 2-8 cm of snow, light wind from the north, alpine high temperatures around -8 C.
MONDAY: Mix of sun and cloud, light wind from the northwest, alpine high temperatures around -8 C.
Avalanche activity is on the decline following the intense storm and avalanche cycle last weekend. During the storm large (size 2) storm slab and very large (2.5-3) deep persistent avalanches occurred naturally. Most notable (and concerning) were reports of deep persistent slab avalanches with 40-200 cm thick crowns. Since then, several size 2 wind slab avalanches have been triggered with explosives and cornices.
While the likelihood of triggering a deep persistent slab avalanche is on the decline, there is still a fair bit of uncertainty about this problem, and the consequences of triggering a very large avalanche are severe.
Upwards of 50-100 cm storm snow is settling around the region. At higher elevations, wind is blowing low density snow into wind slabs and cornices. At lower elevations rain saturated the snowpack up to 1600 m. The bottom 30-50 cm of the snowpack consists of weak facets and crusts, which were the failure plane for recent large (size 2-2.5) deep persistent slab avalanches. The latest forecaster blog discusses managing this complex avalanche problem (check it out here). Snowpack depths range between 80-200 cm around treeline and taper rapidly below.