Avalanche forecast

Northwest Coastal

Apr 3 – 4, 2016Avalanche Canada
View on map
Archived · expired 10 years ago

Avalanche danger

Tue
Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
Open full map

Highlights

The weather over the next  few days will deliver an interesting mix of winter and spring-like conditions. Brief periods of solar radiation may continue to wreak havoc on Monday, so make sure your travel plans allow for changing conditions.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    Large cornices loom over alpine bowls and remain a concern, especially during periods of solar radiation. A cornice fall may be the heavy trigger required to reactivate deeper persistent weaknesses.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Wind speeds and snowfall amounts are uncertain for Monday. I'd be on the look-out for developing storm slabs, especially in wind-loaded terrain. If the sun comes out, loose wet avalanches will be a concern on sun-exposed slopes

Confidence

Moderate - Wind speed and direction is uncertain on Monday

Weather Forecast

10-15cm of new snow is expected between Sunday night and Monday morning. On Monday, expect mainly cloudy skies, light snowfall and the odd sunny break. Heavy mixed rain and snow (up to 40mm each day) is forecast for Tuesday and Wednesday. Ridgetop winds should be moderate from the southwest on Monday, and then become strong with Tuesday and Wednesday's storm. Freezing levels will yo-yo from 1500m on Sunday night to about 1200m by Monday afternoon and Tuesday morning. From there, the freezing level will gradually spike to about 1750m by Wednesday evening.

Avalanche Summary

Over the past week, loose wet avalanches, cornice failures, and deeper persistent slab avalanches to size 3 were observed failing naturally in response to warming and solar radiation. With forecast snow and wind, we are shifting back to a general pattern of storm slab avalanche activity. That said, spring-like loose wet avalanches, isolated persistent slab avalanches and cornice failures will still be possible at elevations where precipitation falls as rain or during periods of warming and solar radiation.

Snowpack Summary

By Monday morning, light to locally moderate amounts of new snow are expected to overlie a widespread melt-freeze crust. Below about 1300m, light rain is expected to further saturate the snowpack keeping the snow loose and unconsolidated. The warm temperatures and sun over the last week woke-up deeply buried weak layers within the snowpack. These includes a weak crust/surface hoar layer which was buried down 30-40cm in the north of the region, a widespread crust/facet layer buried in early February down around 1m, a lingering surface hoar layer from January down over a meter, and weak basal facets at the bottom of the snowpack. Cooling should dramatically limit the reactivity of these old layers; however, they may come back to life during future periods of warming, heavy rain or solar radiation.

Regions covered