Avalanche Forecast
Regions: Coquihalla, Harrison-Fraser, Manning, Skagit.
The March sun packs a punch and can quickly destabilize the snowpack. Be suspect of sunny slopes or overhead hazards like cornices during the heat of the day.
Confidence
Moderate
Avalanche Summary
On Thursday, loose wet avalanches to size 1.5 were observed in steep, solar terrain.
On Tuesday, a natural size 2 wind slab and size 3 glide slab were reported both around 1300 -1500 m. A skier-triggered storm slab was also reported on Zoa. The slab was a size 1.5 and was triggered near the top of the slope with no involvement. It was 40 cm deep and slid clean on the underlying old snow surface. Check out the MIN HERE. Thanks for the report and happy to hear everyone was ok.
A natural persistent slab size 3 was reported on Tuesday but it's suspected that it failed Monday during the storm. This avalanche happened on a shady aspect at 1800 m, with the failure plane unknown but suspect an early March interface.
Natural and human-triggered avalanche activity may occur through the weekend with rising freezing levels and solar radiation.
Snowpack Summary
Daytime warming and solar radiation will promote moist snow surfaces, destabilizing the upper snowpack on all aspects upwards of 1700 m and to ridgetop on solar slopes. Strong southwest winds may have formed reactive wind slabs at higher elevations and cornices loom over ridgelines.
The recent 40 cm of storm snow overlies a variety of old snow surfaces, including a sun crust on solar aspects, a melt-freeze crust at lower elevations and a spotty surface hoar in sheltered locations. Reports indicate that the slab may poor bond to the underlying crust, especially around 1500 to 1800 m.
Additionally several crusts in the mid/lower snowpack. Their depth ranges from 150 to 250 cm. The mid and lower pack is generally settled and bonded in thicker snowpack areas, with a lingering concern for these deeper buried interfaces in shallower snowpack areas.
Weather Summary
Friday night
Scattered clouds and starry breaks. Treeline low temperatures -5. South wind 10-20 km/hr. Freezing level dropping to 1300 m, inversion developing.
Saturday
Mix of sun and cloud. South wind 10-20 km/hr. Treeline high temperature +3. Freezing level 1900 m.
SundayIncreasing cloudiness. Southeast wind 10-30 km/hr. Treeline high temperature +2. Freezing level 1600 m.
MondayWet flurries, 5 mm. South wind 15-30 km/hr. Treeline high temperature +1. Freezing level 1200 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Wind slabs may be poorly bonded to the underlying crust.
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Avalanche Problems
Loose Wet
Strong solar radiation and rising freezing levels will weaken the surface snow creating wet loose avalanches on all aspects up to 1600 m and to ridgetop on steep solar slopes. Be mindful of overhead hazards like cornices.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 1.5
Wind Slabs
Where cold, dry snow prevails, recent moderate to strong southwest winds and 40 cm of storm snow formed wind slabs on lee slopes at treeline and above.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1.5
Persistent Slabs
There are several crusts in the mid-snowpack. Their depth ranges from 50-150+ cm and most likely found in thin snowpack areas or reloaded bed surfaces. A large trigger, such as a cornice fall or a smaller avalanche in motion, could trigger a very large avalanche on one of these deeply buried weak layers.
Glide slabs are unpredictable and may release during the warming.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 2 - 3