Spring-like diurnal conditions exist and the rating reflects the highest hazard level anticipated during the day. Pay attention to steep south facing slopes as they heat up in the afternoon and possibly destabilize. Give looming cornices a wide berth from above and below.
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 1500-2000 m. By Friday the system will bring unsettled weather with new snow and cloudy skies.
Thursday: Mix of sun and cloud. Alpine temperatures near 0 and freezing levels 2000 m. Ridgetop wind strong from the South.
Friday: Mostly cloudy with 5 cm of new snow. Alpine temperatures near -1 and freezing levels 1800 m. Ridgetop wind moderate from the southwest.
Saturday: Mix of sun and cloud. Alpine temperatures near -6 and freezing levels 1500 m. Ridgetop wind moderate from the southwest.
Avalanche Summary
On Tuesday, natural cornice falls were seen. Reports indicated that they did not pull a slab on the slope below. Sunshine and daytime warming may initiate loose wet avalanches on steep solar slopes and continue to weaken cornices on Thursday.
Snowpack Summary
Surface hoar crystals can be found on Northerly aspects above 1800 m combined with dry wintery snow. On solar aspects and at lower elevations expect crusty snow in the morning and soft, moist snow in the afternoon. Large cornices may still pose a hazard close to alpine ridgelines, especially when it's warm and sunny.
A persistent weak layer of facets 40-60 cm deep that was buried in mid-February was reactive in the north of the region earlier this month but since the first week of March, only a couple of avalanches have been reported on this layer resulting from large triggers such as cornice fall. There are several other weak layers deeper in the snowpack composed of old surface hoar, facets and/or crusts, all of which have been recently unreactive.
Terrain and Travel
- A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Avoid exposure to slopes that have cornices overhead.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
Problems
Cornices
Where cornices exist they pose a threat both from the potential 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.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Slopes that face the sun will become unstable as they warm during the day, especially if they are steep.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 18th, 2021 4:00PM
