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
- Extra caution needed around cornices with current conditions.
- Use ridges or ribs to avoid pockets of wind loaded snow.
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
- Be aware of the potential for wide propagations.
- Avoid steep convexities or areas with a thin or variable snowpack.
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
- Pay attention to overhead hazards like cornices which could trigger persistent slabs.
- Watch for clues, like sluffing off cliffs and pinwheeling, that the snowpack is warming up.
- Avoid exposure to sunny slopes.
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 three days. Winds, however, were moderate to strong from the south through to Friday, building fresh wind slabs and further growing cornices.
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
We're looking at a series of weak weather systems for the next few days. Convective activity could result in locally higher accumulations. Temperatures are staying cool for this time of year.
SUNDAY: A mix of sun and cloud with isolated flurries (3-10cm, more possible in the north) / Light to moderate west wind / Alpine temperature -7 / Freezing level decreasing to 1000m
MONDAY: Mix of sun and cloud and occasional flurries / Light to moderate southwest wind / Alpine temperature -7 / Freezing level 1000m
TUESDAY: Cloudy with flurries / Light to moderate west wind / Alpine temperature -5 / Freezing level 1400m
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Recent strong 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.