Avalanche Forecast

Issued: Mar 19th, 2021 4:00PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Email

Potentially touchy wind slabs may form throughout the weekend on upper elevation north, northeast & east facing slopes. These fresh slabs may rest on a thin layer of surface hoar. Convective flurries could produce locally heavy snowfall, watch for rapidly changing conditions. 

Summary

Confidence

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

Weather Forecast

Looks like it’s back to winter for the next few days.

FRIDAY NIGHT: Freezing level lowering to about 600 m, moderate southwest wind with potential for strong gusts, 1 to 5 cm of snow possible with convection possibly delivering as much as 10 cm to favoured locations. 

SATURDAY: Broken cloud cover with potential for some clearing in the early evening, freezing level rising to about 1500 m, moderate southwest wind, 2 to 6 cm of snow expected in most locations. Convective flurries could produce 10+ cm in favoured locations.

SUNDAY: Overcast, freezing level beginning near valley bottom rising to about 1400 m, light to moderate southwest wind, 4 to 10 cm of snow possible during the day with potential for 5 to 10 cm Sunday night.

MONDAY: Broken cloud cover, freezing level beginning near valley bottom rising to about 1500 m, light variable wind, no significant snowfall expected.

Avalanche Summary

Avalanche activity on Thursday was limited to two glide slabs to size 2.5 releasing around 1750 m on steep south facing slopes.

No new avalanche reports on Wednesday, however, there were a few reports of lower elevation (below treeline) that showed evidence of wet slab and loose wet avalanches up to size 2. They proved to be a few days old. 

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. 

On Monday, numerous natural loose wet avalanches were reported from southerly aspects above 1900 m.

Snowpack Summary

Isolated wind slabs may form just below ridgelines with new snow and strong wind this weekend. New snow comes to rest on a variety of old surfaces including surface hoar up to 10 mm in size that exists at treeline and above. Sunny skies and warm temperatures have formed sun crusts on solar aspects at all elevations. A crust exists up to about 2000 m on polar aspects too. 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. 

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Cornices become weak with daytime heating or solar exposure.
  • Rocks will heat up with daytime warming and may become trigger points for loose wet avalanches

Problems

Wind Slabs

An icon showing Wind Slabs

The best riding conditions and the highest hazard will overlap this weekend. High elevation north, northeast and east facing slopes may have a thin layer of surface hoar in place and continued southwest winds are expected to build fresh slabs above this surface hoar. Carefully assess your line for touchy wind slabs before committing. This problem is expected to increase in sensitivity over the next few days as new snow and wind continue to build the slab. Steep, convex slopes below alpine ridge tops are the most likely places to trigger these slabs. 

If the sun pokes out it may have enough punch to initiate the recent snow as loose wet or dry avalanches from steep terrain features. 

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

An icon showing Cornices

Periods of sunshine breaking through the clouds could pack enough punch to increase the likelihood of cornice failures. Recently a cornice fall triggered a very large slab avalanche on the slope below. These events are fairly unpredictable so the best way to mitigate the risk is to minimize your exposure, especially when solar radiation is strong.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Mar 20th, 2021 4:00PM