Avalanche Forecast
Issued: Feb 8th, 2018 5:11PM
The alpine rating is Storm Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
High -
Weather Forecast
Friday: Mainly sunny. Light north winds. Alpine high temperatures of -11 with a temperature inversion building over the day.Saturday: Mainly sunny. Light west winds. Alpine high temperatures around -8 with cooler temperatures at lower elevations due to a temperature inversion.Sunday: Mainly sunny. Light northwest winds. Alpine high temperatures back to around -11 as the temperature inversion breaks down overnight.
Avalanche Summary
No new avalanches were observed on Tuesday or Wednesday, however stormy weather is certain to have obscured visibility. Monday's observations showed further evidence of a natural avalanche cycle from Friday to Sunday. Many slabs were observed, which were expected to have released during the storm. This includes many wind, storm, and persistent slab avalanches, from small to very large (size 1 to 3). The slabs were 30 to 200 cm deep, on all aspects, and most often at upper below treeline, treeline and alpine elevations. Many of the releases propagated far and were highly destructive, such as this one, highlighting the consequences if an avalanche is triggered.Looking forward, dangerous snowpack conditions will persist on Friday as . This trend will likely continue until a more stable weather pattern governs and we see a decrease in avalanche observations. All of our buried weak layers (described in the section below) continue to produce large destructive avalanches from natural and human triggers. Storm and wind slabs have the potential to step down to deeper weak layers, which could produce very large avalanches with high consequences.
Snowpack Summary
Around 30-40 cm of new snow fell during Wednesday's storm. This adds to 50-100 cm of storm snow from the past two weeks that has formed a slab over an unstable snowpack. There are four active weak layers that we are monitoring:1) Around 80 to 140 cm deep, you'll find a layer of crust and/or surface hoar that was buried in mid-January. The surface hoar is found at all elevation bands, and has been especially reactive on north through east aspects between 1900-2600 m. 2) Deeper in the snowpack, the early-January surface hoar layer is found 90 to 160 cm below the surface. 3) Another weak layer buried mid-December consists of a facet/surface hoar/crust combination, which is 120 to 200 cm deep. It has been most problematic at and below tree line.4) A crust/facet layer from late November is yet another weak layer lingering near the base of the snowpack.Each of the above layers have maintained a trend of producing notable avalanche activity and concerning snowpack test results for the past couple of weeks. The wide distribution and ongoing reactivity of these layers suggests that choosing simple terrain is the best avoidance strategy.
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: Feb 9th, 2018 2:00PM