Avalanche Forecast

Archived

Feb 26th, 2014–Feb 27th, 2014

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Sea To Sky.

Above freezing alpine temperatures are expected to continue. Check out the new Forecaster Blog for an update on the “Touchy Weak Layer.”

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Thursday

Weather Forecast

Overnight and Thursday: Warm air is expected to be trapped in the alpine overnight (temperature inversion), and continue to bring above freezing temperatures to the alpine on Thursday. Light Southwest winds are forecast overnight becoming Northerly when the arctic front slides down from the North. There is a chance of flurries Thursday evening depending on the timing of the cooler air.Friday: Freezing levels should drop down to valley bottoms overnight and then rise up to about 1000 metres with strong solar radiation and gusty Northeast outflow winds.Saturday: Clear and cold overnight. Gusty strong Northerly outflow winds becoming light Westerly as cloud moves into the region in the afternoon.

Avalanche Summary

Natural avalanches up to size 3.0 were reported from the Whistler backcountry on Tuesday, these avalanches were sliding on the early February persistent weak layer of facets and crusts. Suspect that loose wet snow is releasing naturally due to above freezing temperatures in the alpine and strong solar radiation.

Snowpack Summary

Strong solar radiation quickly settled the 30-50 cm of recent cold low density new snow. Solar aspects becoming moist and then developing a thin melt-freeze crust during developing cloud in the afternoon. The prominent mid-February weakness, which is primarily a facet/crust combo (with surface hoar in some areas), is now 80-160 cm deep depending on wind exposure. Recent snowpack tests give variable results on this layer, but some observers are still reporting sudden "pops or drops" shears and continue to experience whumpfs. Previous strong winds created wind slabs in exposed lee and cross-loaded terrain, which are now hidden by the dry new snow. The mid and lower snowpack are generally strong and well-settled. Basal facets and depth hoar are likely to exist in some parts of the region; however, skier triggering has become unlikely.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.