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Archived

Avalanche Forecast

Mar 26th, 2013–Mar 27th, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: 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.

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

Avalanche 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