Spring-like diurnal conditions exist and the rating reflects the highest hazard level anticipated during the day with warming. Pay attention to steep south facing slopes as they heat up in the afternoon and 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 thin 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 +2 and freezing levels 2000 m. Ridgetop wind strong from the southwest.
Friday: Mostly cloudy with 5 cm of new snow. Alpine temperatures near -2 and freezing levels 1500 m. Ridgetop wind moderate from the southwest.
Saturday: Cloudy with snow 5-10 cm. Alpine temperatures near -3 and freezing levels 1300 m. Ridgetop wind moderate from the southwest.
Avalanche Summary
On Tuesday, a size 3.5 deep slab avalanche was reported from the Northern Monashees. It was triggered by cornice fall on an east-southeast aspect above 2200 m. Additionally, a natural glide slab size 2.5 was reported from a West aspect at 1500 m and numerous loose wet to size 2 in steep southerly terrain.Â
On Monday, numerous natural loose wet avalanches were reported from southerly aspects above 1900 m.
Isolated loose wet avalanches and cornice failures may continue with warming Thursday.
Snowpack Summary
Snow surfaces vary at the moment. Surface hoar up to 10 mm in size exists at treeline and above. Sunny skies and warm temperatures formed sun crusts on solar aspects and at all elevations and up to 2000 m on polar aspects. Dry snow still exists on north aspects at upper elevations. Large cornices loom over alpine ridgetops.
Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have recently been unreactive and no recent avalanches have been reported on these layers.Â
Terrain and Travel
- Cornices become weak with daytime heating or solar exposure.
- Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
- Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
- Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches
Problems
Cornices
Warm temperatures and sunny skies can increase the likelihood of cornice failures. Recently a cornice fall triggered a very- large slab avalanche from the slope below. These events are fairly unpredictable so the best way to mitigate the risk is to minimize your exposure, especially during the heat of the day.
Aspects: North, North East, East, South East, North West.
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 like moist or wet snow, snowballing or natural avalanche activity. Steep slopes and around rocks will be most susceptible to natural avalanche activity.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 18th, 2021 4:00PM
