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Avalanche Forecast

Archived

Apr 2nd, 2018–Apr 3rd, 2018

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Sea To Sky.

Surface snow conditions are extremely variable. Be alert for rapid changes under your skis or sled, and watch for fresh pockets of wind slab.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

Unsettled weather until the next system arrives on Wednesday. Freezing levels will increase slowly & steadily.TUESDAY: Cloudy with flurries Monday overnight and into the morning (3-6 cm possible) / Light to moderate south west wind / Alpine temperature -7 / Freezing level 1000m WEDNESDAY: Snow (5-10 cm) / Moderate south west wind / Alpine temperature -4 / Freezing level 1300m THURSDAY: Snow (15-25cm) / Light to moderate southwest wind / Alpine temperature -3 / Freezing level 1600m

Avalanche Summary

On Monday, explosives control work triggered only a few size 1 wind slab avalanches in isolated terrain up in the alpine. 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

5-10 cm of new snow fell on Easter Sunday (with some locally higher amounts due to intense convective activity and gusty winds). Winds have been gusting strong, previously from the south and most recently the north.The end result is that snow conditions are wildly variable, ranging from melt freeze crusts on sunny aspects to scoured old hard wind slabs to isolated pockets of soft wind slab. See this MIN post for a good summary of conditions beyond the musical bumps. Old snow from a week ago rests on the March 21st interface, which has a very patchy distribution: 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.The mid and lower snowpack are strong and well settled.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.