Avalanche Forecast
Issued: Jan 20th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Deep Persistent Slabs.
JH,
Avalanche Canada
New snow and wind will continue to add to the load over the early January surface hoar layer. Be extra cautious in windloaded lee terrain, where this layer may be getting buried deeply enough to produce large avalanches.
Summary
Confidence
Moderate
Avalanche Summary
On Friday, we received a report of a skier triggered size 1.5 windslab at the entrance to Nicky's notch.
On Thursday, there was a report of a size 1 skier triggered slab avalanche near the Dome Col, which was was suspected to have failed on one of the surface hoar layers in the upper snowpack.
On Wednesday, a field team today triggered a couple of size 1.0 slab avalanches on small convex rolls at treeline - one of these failed on the Jan 3rd surface hoar layer down 35cm. There was also a MIN report of a skier triggering a similar size 1.0 slab on the Jan 3rd layer on McGill shoulder.
In neighboring areas there are continued reports of isolated human triggering of the recently buried surface hoar layers, as well as natural/explosive triggering of the deep persistent facet layer.
Snowpack Summary
New snow and wind will continue to build the slab over the early January surface hoar layers. These two surface hoar (SH) layers, present in the upper 40cm, have been reactive to human triggering recently.
Recent warm temperatures have left a melt-freeze crust at or near the surface below ~1600m.
The mid-pack facets are slowly rounding and gaining strength, while the basal facets and Nov 17 facet/SH/crust weakness are still reactive when isolated in snowpack tests.
Weather Summary
We're going to get a minor blip of snow (up to 10cm) and gusty SW winds on Saturday, with the passage of a cold front. After that ground hog day continues well into next week, with the same old mixed bag of mostly cloudy skies, isolated flurries, seasonal temps (-10 to -15*C) and light winds.
Terrain and Travel Advice
- Be especially cautious as you transition into wind affected terrain.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Persistent Slabs
Expect renewed reactivity as wind and new snow continue to add to the load on the Jan 3 surface hoar (5-10mm). This layer is buried ~40cm and will be most reactive at ridgeline or in open lee features, where wind has stiffened the surface. If triggered, this slab has the potential to step down to the deep persistent layer.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov 17 layer, which consists of a faceted crust and decomposing surface hoar, highlights a weak basal snowpack. Be particularly cautious in steep, rocky areas with thin snow coverage, where the majority of the snowpack is weak and faceted.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 21st, 2023 4:00PM
