Avalanche Forecast

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

THURSDAY NIGHT: Flurries, 5-10 cm accumulation by Friday morning / moderate southerly wind / alpine temperature low -8 / freezing level valley bottom

FRIDAY: Snow and flurries, 5-15 cm through the day / moderate southwesterly wind / alpine temperature high -4 / freezing level about 700 m

SATURDAY: Flurries, 5 cm / moderate southwesterly wind / alpine temperature high -4 / freezing level around 700 m

SUNDAY: Snow, 20-50 cm / strong southerly wind / ridgeline temperature high +1 / freezing level rising above 1400 m

Flurries and loose snow with fresh wind is encouraging new slabs to form.

On Wednesday skiers triggered size 1-1.5 wind slabs on southerly slopes with 20-40 cm crowns in the Whistler/Blackcomb backcountry. A handful of small (size 1) wet-loose avalanches were also reported.

On Tuesday, sluffing and thin soft slabs were reactive to skiers on north and east aspects, and pinwheeling and loose-dry avalanches were observed in steep and solar features.

A bout of strong northerly winds last Thursday (Feb 11) caused conditions in the region to change rapidly, with new, touchy, and large wind slabs forming in unusual places. Hard, reactive were triggered by skiers resulting in a string of recent serious avalanche accidents. The wind slabs, which were most problematic on southeast, south and southwest facing slopes have decreased in reactivity through the week, however with another pulse of moisture this weekend, new loading could still stress the interface below old, stiff slabs.

On Monday. A size 2 persistent avalanche was triggered by a skier on the west side of Blackcomb Peak, the crown ranged from 5-90 cm and failed on facets. A size 1.5 windslab was remote triggered on the northwest face of Oboe. Additionally, numerous dry-loose avalanches were observed up to size 2, many running far and entraining large amounts of snow. Wet-loose avalanches failed naturally and were reactive to skiers Monday afternoon.

Sunday was a much quieter day for avalanche activity. Avalanche control work produced very small avalanches with the exception being a single size 2.

A fatal avalanche occurred in the region on Saturday in the Brandywine valley. The person caught was carried several hundred meters over steep, rugged terrain and through treed slopes below. The avalanche is described as a size 1 (small) wind slab on a southwest aspect at 1700 m. The incident report can be seen here.

On Friday, a large (size 2.5), fatal avalanche was triggered by skiers at 2200 m on a west-facing slope on Phalanx Mountain. The avalanche is described as a wind slab that formed to the lee of recent strong east winds. Two people out of a group of three were involved in the avalanche and one person was killed. The incident report can be seen here. A second, smaller (size 1.5) wind slab was triggered by skiers on a nearby slope, again causing injury to the person involved.

Thursday, two skiers were involved in an avalanche in the Supercouloir feature of Mamquam Mountain. This avalanche was a natural wind slab release and again resulted in serious injuries and an urgent evacuation by helicopter 

Surface hoar growth was noted on Wednesday and Thursday morning following cool, clear nights. This could be quite a reactive weak layer with new snow, especially where it sits on a crust.

10-30 cm fresh flurries and loose snow sits over over a variety of wind affected surfaces and facets in the alpine and into treeline, and a crust on solar features. Isolated wind slabs from recent outflow winds are now burried 20-40 cm. Fresh southerly winds are impacting loose snow, forming thin new windslabs and hiding those older, stiffer slabs. Below 1800m, a crust is under the new flurries.

Below the evolving surface, 50-100 cm of settled storm snow sits on a persistent weak layer from late January that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1900 m, and a sun crust on south-facing slopes. There could be more than 100 cm on this layer in wind loaded areas. Although this structure is suspect, we have no recent reports of avalanches failing at this interface within the region.

A crust from early December, currently considered dormant, may be found around 200+ cm deep in the snowpack.

• Recent new snow may be hiding windslabs that were easily visible before the snow fell.
• Recent wind has varied in direction so watch for wind slabs on all aspects.
• Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
• Closely monitor how the new snow is bonding to the crust.
• Watch for fresh storm slabs building throughout the day.