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Archived

Avalanche Forecast

Apr 1st, 2018–Apr 2nd, 2018
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Sea To Sky.

Caution on shady aspects in the alpine and tree line elevation bands where a persistent weak layer may be reactive. See Friday's Forecaster Blog for more details: goo.gl/8Z83CvAvoid sunny slopes if the sun does come out in full force.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

Monday will see mixed weather before a more organized system arrives on Wednesday. Convective activity could result in locally higher accumulations. Temperatures are staying cool for this time of year. MONDAY: Mix of sun and cloud and occasional flurries in the afternoon / Light to moderate southwest wind / Alpine temperature -8 / Freezing level 1000m TUESDAY: Cloudy with flurries (2-5 cm possible) / Light to moderate south west wind / Alpine temperature -7 / Freezing level 1100m WEDNESDAY: Snow (10-20cm) / Moderate south west wind / Alpine temperature -4 / Freezing level 1300m

Avalanche Summary

On Friday a sled-triggered size 2 wind slab was reported near Grizzly Lake near Powder Mountain, on a north west aspect near 1750m. See the MIN post for more details. On Thursday several natural avalanches to size 2.5 were reported in the Tantalus Range. See the MCR for more details. On Wednesday there was a size 1 avalanche that sympathetically triggered a size 3 persistent slab avalanche resulting in a fatality. This was on a northeast aspect at 2000m, 50cm deep. Additionally there were reports of natural persistent slab avalanches size 2.5-3 on southeast through northeast aspects between 1800 and 2000m. These were reported to have happened in the previous 24-48 hours. See this MIN post for similar details.

Snowpack Summary

We've seen only trace amounts of new snow in the past four days, although convective activity on Sunday could produce local amounts of 10-15cm. Winds, however, were once again moderate to strong from the south / southwest Saturday night, keeping wind slabs in the front of our minds and further growing cornices.Sunny aspects have been through a melt-freeze cycle over the past few days, in addition to likely being wind scoured. Last week's storm snow was redistributed by moderate to strong southwest winds. This snow rests on the March 21st interface, a mix of moist grains at low elevations, crusts on solar aspects at all elevations and surface hoar/facets on north/east facing features at treeline and alpine elevations. Some west facing features may have surface hoar on top of a crust. The March 21st interface has been giving variably moderate to hard sudden planar results, typically down 50-60cm on 1-2mm facets.Deeper in the snowpack, 80 to 140 cm below the surface is a combination of facets, surface hoar, and/or crust known as the mid-February layer. This interface has not been active recently.The mid and lower snowpack are strong and well settled.

Avalanche Problems

Wind Slabs

Recent strong south / west winds have formed wind slabs in the lee of terrain features. These may be most reactive where they may be sitting on a thin and weak layer of facetted crystals on shady aspects.
Use ridges or ribs to avoid pockets of wind loaded snow.Extra caution needed around cornices with current conditions.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer of surface hoar or facetted crystals has become reactive especially where it may be sitting on a hard crust.
Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for wide propagations.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3

Loose Wet

The sun could make an appearance this weekend: if it does, it will pack a punch and weaken surface snow layers.
Avoid exposure to sunny slopes.Watch for clues, like sluffing off cliffs and pinwheeling, that the snowpack is warming up.Pay attention to overhead hazards like cornices which could trigger persistent slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1.5