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Avalanche Forecast

Archived

Mar 17th, 2023–Mar 18th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Spearhead.

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.

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

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.