Avalanche Forecast
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/8Z83Cv
Avoid sunny slopes if the sun does come out in full force.
Avalanche Problem 1: Wind Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
Travel and Terrain Advice
- Use ridges or ribs to avoid pockets of wind loaded snow.
- Extra caution needed around cornices with current conditions.
Avalanche Problem 2: Persistent Slabs
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
A weak layer of surface hoar or facetted crystals has become reactive especially where it may be sitting on a hard crust.
Travel and Terrain Advice
- Avoid steep convexities or areas with a thin or variable snowpack.
- Be aware of the potential for wide propagations.
Avalanche Problem 3: Loose Wet
What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?
The sun could make an appearance this weekend: if it does, it will pack a punch and weaken surface snow layers.
Travel and Terrain Advice
- 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.
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.
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
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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.