Avalanche Forecast
Issued: Jan 27th, 2018 4:43PM
The alpine rating is Storm Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Sunday: 5-10 cm snow. Moderate south-westerly winds. Alpine temperature near -7.Monday: 15-20 cm snow. Moderate to strong south-westerly winds. Alpine temperature warming to near -3.Tuesday: Light snow (5cm possible). Light to moderate southerly winds. Alpine temperature -4. More information can be found in the Mountain Weather Forecast.
Avalanche Summary
Avalanche activity slowed on Thursday and Friday, but a few size 2.5-3 naturally and explosive-triggered slabs have been reported. These were around 120 cm deep and are suspected to have failed on the early January persistent weak layer. On Monday, there was evidence of a widespread natural avalanche cycle with very large avalanches being released (up to size 3.5). This occurred on all aspects, at all elevations, with depths of 40 to 100 cm, and generally occurring on the mid-January weak layer but sometimes on the mid-December layer. Also, a large (size 2.5) persistent slab avalanche was triggered by a skier at treeline, which stepped down to the mid-December weak layer. The slab was 65 cm deep and slid on a 30 to 35 degree north-facing slope.Although natural avalanche activity has diminished, there's still a good chance of triggering a surprisingly large avalanche with the weight of a person.
Snowpack Summary
The current snowpack is complex, with three active weak layers that professionals are monitoring. Recent storm snow has been shifted by winds to form wind slabs and cornices.Down about 30-70 cm is a crust and/or surface hoar layer buried mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The surface hoar is up to 10 mm is size and has been reported at all elevation bands.Deeper in the snowpack, the early-January persistent weak layer is found 40 to 120 cm below the surface. It is composed of surface hoar on sheltered slopes and sun crust on steep solar aspects and found at all elevation bands. Snowpack tests show sudden fracture characters with easy to moderate loads and high propagation potential, as well as whumpfs and cracking with skier traffic. Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 40 to 100 cm deep. It is most problematic at and below tree line.A rain crust buried in November is 100 to 150 cm deep and is likely dormant for the time being.See here for a good summary of snowpack test results.
Problems
Storm Slabs
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 28th, 2018 2:00PM