Bulletin d’avalanche

Long Range Mountains

Feb 18 – 21, 2023Avalanche Canada
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Archivé · expiré 4 years ago

Danger d’avalanche

Mon
Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
Sans niveau
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Points saillants

Dramatic changes in weather and avalanche danger this week.

Be aware of wind loaded features on Sunday, squalls may rapidly build wind slabs in localised terrain.

Avoid avalanche terrain on Monday afternoon, heavy rain and snow is expected to produce natural avalanche activity. By Tuesday morning expect a refrozen surface crust making travel difficult.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Expect small pockets of wind slab where loose snow is available for transport (think areas unaffected by Wednesday's rain, and where there is fresh snowfall).

    Where wind loading sits over a crust, expect slabs to be smaller but possibly more reactive. Where the crust is not present, loading will build over older and larger wind slabs that are more stubborn to rider triggers, likely found on many aspects.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely - Certain
    Taille
    1–2.5

    Heavy rain, wet snow and warm temperatures on Monday afternoon will rapidly increase avalanche danger.

    Wet avalanches may only involve the surface snow initially, but as rainfall continues to saturate the snowpack expect larger avalanches. Avoid avalanche terrain, wet or slushy surface snow will quickly lose cohesion.

Confidence

Moderate

Avalanche Summary

Small natural and rider triggered avalanches are expected in wind affected features with new snow and wind from Friday and Saturday. Slab avalanches have been reported over the last week, naturally triggered and ranged from size 1-2.5. Check out these MINS for more details: near Glenburnie, Gros Morne, Western Brook Gorge.

A widespread natural avalanche cycle is expected in the afternoon on Monday and overnight, as rainfall saturates the snowpack.

Snowpack Summary

By Sunday morning up to 15 cm of dry snow can be found, likely redistributed into deposits on south and east facing slopes by northwest winds. This sits over dense wind affected snow at higher elevations, and over a melt freeze crust at lower elevations. This crust varies throughout the region (likely more prominent in the south) and may form a good bed surface for avalanche activity. Highly variable amounts of wind affected snow make up the rest of the upper snowpack.

Heavy rain and warm temperatures forecast overnight Monday will saturate the upper snowpack and likely refreeze by Tuesday morning creating a thick surface crust.

A hard melt freeze crust sits in the middle to lower snowpack. Depending on wind loading, this crust is anywhere from 10 cm to over 100cm deep. A weaker layer of faceting crystals sits immediately above this crust, thought to be bonding well. Avalanche activity is possible on this layer where a weaker bond exists, more likely in shallow snowpack areas. The snowpack below this crust is dense and well bonded from previous rainfall.

Weather Summary

Saturday Night

Mostly cloudy. Flurries begin around midnight delivering 2-5 cm by morning. North-west winds 50 km/hr.

Sunday

Mostly cloudy with flurries possible bringing up to 3 cm. Squalls are possible, delivering up to 10 cm to affected terrain features. Winds 50km/hr from the west. High temperatures around -9 °C.

Monday

Strong southerly winds reach 120 km/hr, and freezing levels rise gradually over the day. Cloudy with snowfall beginning around midday. 10-15 cm of snow is likely, before snow turns to rain in the early afternoon with another 15 mm possible before evening.

Freezing levels rise toward 1000-1500 m and a further 20-30 mm of rain is expected overnight, heaviest in the south.

Tuesday

Freezing levels rapidly fall back to valley bottom over the morning. Winds shift to 50 km/hr westerly. Flurries are possible.

Outlook

Temperatures remain cold this week a mix of sun and cloud. Light snowfall possible on Thursday.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Keep in mind that wet avalanches can be destructive due to their high density.
  • Avoid avalanche terrain during periods of heavy rain.

Régions couvertes