Avalanche Forecast

Issued: Mar 24th, 2018 4:33PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Wind Slabs and Loose Wet.

mgrist, Avalanche Canada

Purcells.

The 'first kiss of the sun' on fresh snow can rapidly destabilize the surface snow layers. Be vigilant to warming effects and also lingering wind slabs at higher elevations.

Summary

Confidence

Low - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

We're looking at unsettled weather, sunny breaks and the chance of convective flurries throughout the forecast period. SUNDAY: Sunny with cloudy breaks. Light southwest winds 10-20 Km/hr. Freezing level to 1300 metres with alpine high temperatures around -5.MONDAY: Cloudy with isolated flurries (5 cm possible). Moderate southwest winds. Freezing level to 1400 metres with alpine high temperatures of -4.TUESDAY: Occasional flurries (5cm). Moderate to strong west winds, Freezing level to 1700 metres with alpine high temperatures around -2.

Avalanche Summary

On Saturday, skiers were able to cut a size 1.5 wind slab on a north west aspect (crown height 10-15cm) in the east of the region. Thursday's reports included a couple of smaller (size 1-1.5) wind slabs as well as several natural size 1 loose wet releases on south aspects. The slabs were skier triggered and ski cut on north to northwest aspects in the alpine.Looking forward, newly formed wind slabs are likely to remain reactive to human triggering over the near term. Watch for intervals of solar exposure to destabilize slabs as well as promote loose wet avalanche conditions on steeper, sun-exposed slopes.

Snowpack Summary

Convective snowfall coupled with strong southerly winds brought a wind-affected 10-20 cm of new snow to the region since Thursday night. The new snow has buried a couple of recent layers of storm snow that are separated by temperature and sun crusts at lower elevations and on south aspects. Surface hoar layers have been reported between these storm snow layers on shaded aspects at higher elevations and can likely now be found at approximately 20 and 40 cm below the surface.New snow amounts taper with elevation and below about 1900 m, reduced accumulations have buried a supportive crust on all aspects. Deeper persistent weak layers from mid-late February (down 40 -100 cm deep) as well as January and December layers are generally considered dormant, but could wake up with a surface avalanche stepping down, cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets also linger at the base of the snowpack.

Problems

Wind Slabs

Strong winds blew new snow into wind slabs that are likely to remain reactive to human triggering on Saturday. High north aspects are a special concern for the presence of buried surface hoar that could lead to easier triggering and deeper releases.

Give cornices a wide berth when travelling on or below ridges.Use extra caution around high, sheltered north aspects where slabs may overlie surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

The sun's direct effect could rapidly destabilize the snowpack. It's best to stick to north facing terrain if the sun comes out in full force.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 25th, 2018 2:00PM