Avalanche Forecast

Issued: Mar 26th, 2013 8:06AM

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

sylvia forest, Parks Canada

Glacier.

Spring conditions: cold nights, warm days, crusts and cornices. High elevations and north aspects will likely remain cool, but conditions will change rapidly at lower elevations and throughout the day.

Summary

Weather Forecast

A ridge of high pressure remains over the area today, bringing mainly sunny skies, freezing levels to 1500m, light winds, and potentially intense solar radiation. A disturbance will move through tonight. Wednesday will see a mix of sun and cloud.

Snowpack Summary

Solar aspects have a series of buried sun crusts, some of which have surface hoar on top, creating potential for wide avalanche propagation with the right trigger. These aspects also tend to be windward (SW) so the snowpack is thinner there, and may be more easily triggered by skiers. Strong daytime warming will weaken the snow.

Avalanche Summary

A few very large avalanches were observed in the Selkirks yesterday. Most of these were triggered by cornice failures. One size 3 was observed from MacDonald into the highway corridor - quite impressive. Skiers triggered an avalanche two days ago on a west aspect, in a thin snowpack area. It failed on a suncrust with surface hoar on top.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Cornices

Cornices are large and unsupported. Wide fluctuations in diurnal temperatures is likely increasing their fragility. Ski tracks on the Sifton Traverse yesterday passed within arms reach of van-sized cornice chunks, with densities of ice. Yikes!

Cornices become weak with daytime heating, so travel early on exposed slopes.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 4

Persistent Slabs

Slopes receiving direct sun become more reactive during the day with warming. This is especially likely on steep solar aspects where buried crusts exist. Solar triggered avalanches are most likely around exposed rocks and may trigger deeper slabs.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Wet

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 27th, 2013 8:00AM