Avalanche forecast

Northwest Inland

Apr 3 – 4, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

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

Avalanche problems

  • Wind Slabs

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

  • 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.

Confidence

Moderate - Forecast snowfall amounts are 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. Moderate mixed rain and snow (up to 15mm each day) is forecast for Tuesday and Wednesday. Ridgetop winds should be strong from the southwest on Monday, and the become extreme and southwesterly on Tuesday and Wednesday. 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 1800m 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 snow and wind expected throughout the forecast period, 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, 5-15 cm of new snow is 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. This includes a weak crust/surface hoar layer which was buried down 20-30cm in the north of the region, a widespread crust/facet layer buried in early February down up to 1m, a lingering surface hoar layer from January down around 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