Avalanche Forecast

Issued: Mar 15th, 2019 5:28PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Loose Wet.

cgarritty, Avalanche Canada

Sea To Sky.

The first big warm up of spring is underway. Loose wet avalanches will be an increasing concern on Saturday. Rising temperatures and weak overnight cooling will bring our most recent weak layer back into the spotlight early next week.

Summary

Confidence

Moderate -

Weather Forecast

Friday night: Mainly cloudy. Light south winds. Freezing level remaining near 1000 metres.Saturday: Mainly cloudy with a chance of isolated wet flurries, or rain below about 1500 metres. Light south or southwest winds. Alpine high temperatures around 0 with freezing levels rising to 1900 metres, remaining elevated overnight.Sunday: A mix of sun and cloud with cloud decreasing over the day. Light east winds. Alpine high temperatures around +4 with freezing levels rising to 2500 metres by end of day, increasing overnight.Monday: Sunny. Light southeast winds. Alpine high temperatures around +8 with freezing levels reaching 3300 metres, remaining elevated overnight.

Avalanche Summary

This MIN report from Thursday describes southwest winds promoting wind slab formation in the Whistler area, with ski cuts easily producing small 20-40 cm-deep slab releases on steeper slopes. Wednesday was an active day for avalanche activity. Loose wet releases were common on steep solar aspects to size 2. This MIN from Decker Meadows does a great job of showing just how quickly the very strong spring sun can produce avalanches with some great photos and a positive outcome. We suspect activity like that described in this MIN will probably pick up over the next few days as the region warms considerably. A size 2 natural wind slab avalanche was reported from a north facing feature at 1900 m. A size 1 remote triggered storm slab avalanche was also reported from a north facing feature between 2200 and 2000 m.Small loose wet avalanches were reported on Tuesday on south-facing slopes. There was also a size 1.5 remote-triggered avalanche reported at 1400 m.During the previous storm, there was an avalanche cycle to size 2.5. Operators noted some avalanches showed wide propagations.

Snowpack Summary

Another 15-20 cm new snow added to previous amounts to give storm totals in the range of 30-50 cm. Towards the end of the storm, winds shifted to the north, potentially creating some unusual wind slabs on south-facing slopes. Beneath the recent snow you may find hard wind-affected snow at higher elevations, soft faceted snow in shaded and sheltered areas, and crusts on steep southerly slopes. The middle and lower snowpack is well-settled.

Problems

Wind Slabs

Winds shifted to the north at the end of the last storm, building wind slabs on south-facing slopes. These wind slabs have proven susceptible to human triggering and the increasingly strong spring sun is capable of producing natural avalanches too.

Be careful with wind slabs that recently formed in steep, unsupported and/or convex terrain featuresApproach lee and cross-loaded slopes with caution.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Weak overnight cooling and steadily increasing temperatures will be increasing the chances of loose wet avalanches over the coming days. Loose wet avalanches may occur naturally or with a human trigger as heat destabilizes surface snow.

Loose avalanches may start small but they can grow and push you into dangerous terrain.Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.Back off slopes that become moist or wet with rising temperatures.

Aspects: East, South East, South, South West, West.

Elevations: Treeline, Below Treeline.

Likelihood

Likely

Expected Size

1 - 1.5

Valid until: Mar 16th, 2019 2:00PM