Avalanche Forecast

Issued: Apr 5th, 2021 4:00PM

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

Avalanche Canada swerner, Avalanche Canada

Email

Periods of sunshine can pack a punch and trigger natural avalanches and cornice fall. Give cornices a wide berth from above and below. 

Pockets of wind slab may exist on leeward features in the alpine and could be triggered by the weight of a person. 

Summary

Confidence

High -

Weather Forecast

The region will start to see the effects of the next frontal system by late Tuesday. This will bring moderate snow amounts accompanied by strong southwest wind.

Tuesday: Mix of sun and cloud with light snow up 5-10 cm. Ridgetop wind strong from the southwest. Alpine temperatures near -6 and freezing levels 1700 m. 

Wednesday: Snow 10-20 cm. Ridgetop wind moderate to strong from the southwest. Alpine temperatures -7 and freezing levels 1400 m. 

Thursday: Mix of sun and cloud with a trace of new snow. Ridgetop wind light from the southwest. Alpine temperatures near -7 and freezing lvels 1300 m. 

Avalanche Summary

On Monday, reports from our Field team in the Dore river area noted evidence of loose-wet avalanches up to size 2 and some cornice falls. One larger slab avalanche (several days old) size 2.5 was also seen on a steep East aspect in the alpine. 

Reports from Sunday noted that the recent snow (10-20 cm) was sluffing from steep terrain features and loose-wet avalanches were seen up to size 1 from solar aspects below 1800 m. The recent snow from Sundays' storm seems to be bonding to previous snow surfaces. 

Cloud cover, a bit of new snow, and strong southwest wind are expected to keep snow surfaces cool on Tuesday. Natural avalanche activity may taper. However; things can change rapidly and if the sun shines, natural avalanche activity and cornice failures may spike. 

We regret to report a fatality on Eureka Peak, east of Williams Lake on March 29. A human-triggered cornice failure resulted in a size 2.5 slab avalanche. It is important to remember to stay well back from ridgetops that might be corniced and to avoid slopes with overhead cornice exposure especially under the current conditions where recent rapid growth has made them large and fragile.

Snowpack Summary

10-20 cm of recent snow accompanied by strong southwest wind may have formed wind slabs on leeward slopes at upper elevations. Reports indicate that this recent snow is bonding to a variety of underlying surfaces which include wind-affected snow in the alpine, crust on solar aspects, and below 1900 m. Below this elevation and on solar aspects the new snow dusts crusty surfaces down to 1500 m. Below 1500 m, the moist snowpack is quickly diminishing.

Recent warm weather is expected to have helped old persistent weak layers heal, including a few crusts buried over the last month as well as a facet layer 150 cm deep from the mid-February cold snap.

Terrain and Travel

  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Cornices

An icon showing Cornices

Cornices become weak with daytime warming. Cornice falls are dangerous in their own right and they can also trigger slabs on slopes below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs

Wind slabs will be most likely be isolated to immediate lees of ridgecrests and roll-overs in wind exposed alpine terrain.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Apr 6th, 2021 4:00PM