Avalanche Forecast
Issued: Mar 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Wet and Cornices.
swerner,
Avalanche Canada
New snow and strong wind may form isolated pockets of fresh wind slab.
The region will mostly see cloud cover on Thursday, however; if the sun pokes through it could heat slopes quickly. Pay attention to steep South facing slopes and back off them if they heat up.
Summary
Confidence
Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
A Pacific frontal system approaching the coast on Thursday will start to force some upper-level cloud cover to the Interior Mountain Ranges. Freezing levels will be between 1500-1800 m. By Friday the system will bring unsettled weather with new snow and cloudy skies.
Thursday: Mix of sun and cloud with snow up to 5 cm. Alpine temperatures near -5 and freezing levels 1800 m. Ridgetop wind light from the South.
Friday: Mostly cloudy with another 5 cm of new snow. Alpine temperatures near -5 and freezing levels 1400 m. Ridgetop wind moderate from the South.
Saturday: Cloudy with sunny periods and flurries. Alpine temperatures near -11 and freezing levels 1200 m. Ridgetop wind moderate from the southwest.
Avalanche Summary
No additional avalanche observations reported Tuesday.Â
Wind slabs may be reactive on Thursday in areas that receive some fresh snow and strong wind. These will likely be isolated to the immediate lee of ridgetop features. Daytime warming combined with solar radiation may pack enough punch to trigger loose wet avalanches, especially on sunny aspects. Large looming cornices may also become weak and fragile with warming.Â
Snowpack Summary
Strong ridgetop wind accompanied by 5-10 cm of new snow is expected for Thursday. This may form fresh wind slabs below alpine ridgetops. Dry snow can be found on north aspects and crusty snow surfaces exist on solar aspects. Large cornices loom over alpine ridges and become weak with afternoon warming.
A persistent weak layer made up of surface hoar at treeline elevations and a crust with facets in the alpine on solar aspects can be found down 50-150 cm in some parts of the region. Only one recent avalanche has been reported on a deeper layer and this involved a very heavy trigger (a cornice).
Terrain and Travel
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Problems
Wind Slabs
Increasing winds on Thursday accompanied by 5-10 cm of new snow may form wind slabs in isolated alpine locations. Steep, convex slopes below alpine ridgetops are the most likely places to trigger these slabs.
If the sun pokes out it may have enough punch to initiate the recent snow as loose wet or dry avalanches from steep terrain features.
Aspects: North, North East, East.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Loose wet avalanches may occur during the heat of the day and primarily on solar aspects. Watch for changing snow surfaces while traveling like moist or wet snow, snowballing, or natural avalanche activity. Steep slopes and around rocks will be most susceptible to natural avalanche activity.
This may only become a problem when the sun is out.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Where cornices exist they pose a threat both from the potential for them to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. If anything can trigger the more stubborn persistent weak layers it's a large falling cornice. They are most likely to fail during the heat of the day.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 18th, 2021 4:00PM
