Avalanche Forecast

Issued: Mar 20th, 2021 4:00PM

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

Avalanche Canada dsaly, Avalanche Canada

Email

More snow is forecasted around the region with enhanced precipitation in localized areas. Expect to find an increasingly reactive slab as snowfall accumulates and anywhere fresh snow is influenced by the wind.

Summary

Confidence

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

Weather Forecast

SATURDAY NIGHT: Flurries, 5-15 cm. Light to moderate northwest wind, alpine temperature low -6C, and freezing level dropping to valley bottom.

Weather models are showing a band of moisture moving from the Shuswap to the Purcells through the Nakusp area late Saturday evening and overnight, and may produce enhanced precipitation in localized areas of up to 25cm. 

SUNDAY: Snow and flurries, with up to 25 cm accumulating by the evening. Highest precipitation amounts are forecasted for the Monashees and southwest of Revelstoke. Moderate southwest wind, alpine high -3C, and freezing level beginning near valley bottom rising to about 1100 m.

MONDAY: Cloudy with sunny breaks and isolated flurries, up to 10 cm of snow possible. Light northwest wind, alpine high -4C, and freezing level beginning near valley bottom rising to about 1300 m.

TUESDAY: Mostly sunny with patchy clouds. Light to moderate southwest wind, alpine high +1C, and freezing level beginning near valley bottom rising above 1500 m.

Avalanche Summary

On Friday, several glide slab avalanches (size 2-3) were observed on south and east aspects around the TCH highway corridor. Loose wet avalanches up to size 2.5 were reported around the region; a natural loose-wet cycle was reported around Rogers Pass initiating with evening rainfall.

On Thursday several loose wet avalanches to size two were reported on solar alpine features. Pin wheeling was also noted on north aspects below 2000 m in the afternoon.

On Wednesday a few loose-wet avalanches were seen on steep solar aspects below treeline. 

On Tuesday, a natural 1.5 loose wet avalanche was reported from steep rocky terrain and small loose-dry sluffs were easily triggered by skier traffic on northerly aspects. 

Snowpack Summary

10-20 cm fresh snow accumulated around the region through Saturday with more forecasted through Sunday. Flurries and wind formed fresh slabs in immediate lees. 

New snow covers dry settled snow and surface hoar up to 10 cm on northerly aspects above 2000m, and crusts on solar aspects and lower 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

  • Dial back your terrain choices if you are seeing more than 25cm of new snow.
  • Closely monitor how the new snow is bonding to the old surface.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.

Problems

Storm Slabs

An icon showing Storm Slabs

Slabs will become increasingly reactive as snowfall accumulates. The deepest and most reactive deposits will be in areas affected by wind - expect to find touchier slabs around ridges and in lee features.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1.5 - 2.5

Cornices

An icon showing Cornices

Where cornices exist they pose a threat both from the potential for them to collapse under your feet (or machine) and from the potential to send large chunks of snow far down a slope. They are most likely to fail during periods of solar radiation or loading from snow/wind.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Mar 21st, 2021 4:00PM