Avalanche Forecast

Issued: Mar 17th, 2023 4:00PM

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

Avalanche Canada dsaly, Avalanche Canada

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The March sun packs a punch and can quickly destabilize the snowpack. Be suspect of sunny slopes or overhead hazards like cornices during the heat of the day.

Summary

Confidence

Moderate

Avalanche Summary

On Thursday, relative wind slabs were reported around Whistler-Blackcomb including a size 1.5 in the Poop Chutes and a size 1.5 in S Turn (Wayne Flann Blog).

On Wednesday, skiers triggered a size 1 storm slab on a convex rollover with a crown 10-30 cm deep near Rainbow Mountain. Additionally, a few natural wind slabs were reported up to size 1 and explosive control produced several cornice falls up to size 2.5 and wind slabs to size 1.

In the northernmost end of the forecast region (near the Homathko Icefield), skiers found a reactive layer of surface hoar buried 65 cm deep below the recent storm snow, and observed natural avalanches to size 3.

On Tuesday, a few human-triggered storm and wind slab avalanches were reported up to size 2. Natural cornice failures and dry loose avalanches were also seen to size 1.

Natural and human triggered avalanche activity is possible throughout the weekend with rising freezing levels and solar radiation.

Snowpack Summary

Surface snow will likely become moist to ridgetop on solar aspects by the afternoon. Cornices loom over ridgelines and may become weak during periods of solar radiation and warming.

Up to 40 cm of recent storm snow seems to be settling and bonding to the old buried snow surfaces which consist of crusts on solars and faceted snow on polar aspects. However, at upper elevations shady, sheltered aspects may still host fairly unconsolidated loose snow. Recent southwest wind formed reactive wind slabs on lee slopes at treeline and in the alpine.

Deeper in the mid-pack a couple of crusts with facets sitting above them can be found at treeline and above down 90 to 200 cm.

The remainder of the mid and lower snowpack is well-settled and strong.

Weather Summary

Friday night

Scattered clouds and starry breaks. Treeline low temperatures -6. Southeast wind 10-20 km/hr. Freezing level 1000 m.

Saturday

Mix of sun and cloud. South wind 10-25 km/hr. Treeline high temperature +4. Freezing level 1700 m.

Sunday

Flurries start late in the afternoon. Southeast wind increasing to 20-30 km/hr. Treeline high temperature +2. Freezing level 1600 m.

Monday

Flurries, up to 10 cm. South wind gusting to 30 km/hr. Treeline high temperature 0. Freezing level 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Closely monitor how the new snow is bonding to the crust.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

Wind Slabs

An icon showing Wind Slabs

Recent southwest winds have formed wind slabs on lee slopes at treeline and above and may remain reactive to human triggering. In wind-sheltered terrain, the recent storm snow may have a poor bond to the underlying crust.

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

An icon showing Loose Wet

Strong solar radiation and rising freezing levels may weaken the surface snow creating wet loose avalanches from steep solar slopes.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 1.5

Cornices

An icon showing Cornices

Large looming cornices exist along ridgelines. Cornices become weak with daytime warming and sun exposure. Give cornices a wide berth while traveling ridgelines and avoid slopes below them.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Mar 18th, 2023 4:00PM

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