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Avalanche Forecast

Archived

Apr 18th, 2021–Apr 19th, 2021

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

Regions

Sea To Sky.

Start (and finish) your day early to avoid exposure to sun-exposed avalanche terrain. Steer clear of cornices overhead and plan your egress route carefully.

Confidence

High - Confidence is due to a stable weather pattern; little change is expected for several days.

Weather Forecast

Sunday night - Clear / light to moderate northeast wind / alpine low temperature 0 / freezing level dropping to 2500 m. Areas further inland like Whistler may see freezing levels drop to 1200 m overnight.

Monday - Sunny / light wind / alpine high temperature near 0 / freezing level 2300 m

Tuesday - Sunny / light wind / alpine high temperature near +1 / freezing level 2500 m

Wednesday - Sunny / light wind / alpine high temperature near +2 / freezing level 2600 m

Avalanche Summary

Over the weekend, multiple large to very large wet slab avalanches were observed near Whistler, size 2-4. Many of these involved the full depth of the snowpack, running to valley bottom.

 

Solar triggered wet loose avalanches have been reported each day over the past week up to size 2.5. There have also been a number of cornice failures reported over the past week.

Snowpack Summary

Radiant cooling and (finally) a slight dip in freezing levels overnight have likely formed a thin surface crust in many areas. It should quickly soften during they day with sunshine and warm temperatures. Steep north aspects at the highest elevations may still hold dry snow.

Cornices are large and looming along ridgelines. Sun and warm temperatures will increase the chances of cornice failures, especially when temperatures remain above zero overnight.

Terrain and Travel

  • Avalanche hazard is expected to to increase througout the day, think carefully about your egress.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Keep in mind that wet avalanches can be destructive due to their high density.
  • Avoid lingering or regrouping in runout zones.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.