Avalanche Forecast
Issued: Jan 26th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
CB,
Avalanche Canada
Warm temps, fresh storm snow and gusty winds are a perfect combo for building reactive slabs.
Watch for signs of instability, such as recent avalanches, shooting cracks, hollow sounds and whumphing.
Summary
Confidence
Moderate
Avalanche Summary
Thursday: Small cycle of natural activity along the highway corridor, up to size 2.5, primarily in steep N facing terrain off Mt. Macdonald. Triggered by consistent moderate winds.
Wednesday: Skier accidental from McGill shoulder, triggered on the surface hoar down 50cm. Parks Canada staff triggered soft slabs, up to size 1, down 30-40cm on a sun crust at treeline. And sluffing in steep terrain.
Wednesday: small natural cycle, size 2-2.5, along the highway corridor from south facing terrain. Triggered by wind loading and sun effect midday.
On Monday, both natural and skier triggered avalanches were observed on wind slabs.
Snowpack Summary
Wind slabs in the alpine and treeline on lee features. Warm storm snow is building a slab with moist snow/crusts below 1700m and sun crusts on steep, solar facing terrain. This sits on top a Jan 21 sun/temperature crust down ~30-40cm.
The Jan 3 surface hoar, which most likely to be rider triggered at treeline, is down 50-70cm.
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
A final cold front moving over the region will bring snow through Friday. A cold, dry arctic air mass will arrive on the weekend.
Tonight: Snow, 5-10 cm, Alp Low -6*C, 1000m Freeze Level, Light to Mod W winds.
Fri: Cloudy w/flurries, Alp high -5*C, 1200m FZL, Light to Mod N winds
Sat: Sunny, Alp high -17*C, FZL, Valley Bottom, Light NE wind.
Terrain and Travel Advice
- Watch for newly formed and reactive wind slabs 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
Wind Slabs
Southerly winds are building wind slabs at ridge-lines, lee areas, and cross loaded features. Watch for reactive wind slabs in this terrain. A thin crust down 30-50 cm could increase the likelihood of triggering.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
The depth and warm storm slab overlying this layer, makes perfect conditions for triggering this layer where it persists. It is most reactive at ridgeline or in open lee features where new wind slab has formed on top of it. 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 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 27th, 2023 4:00PM
