Avalanche Forecast

Issued: Feb 26th, 2018 5:35PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

ghelgeson, Avalanche Canada

Sea To Sky.

Wind slabs formed on Sunday may remain sensitive to human triggering and west/northwest wind Tuesday could form fresh shallow wind slabs. Seek out wind sheltered terrain and avoid slopes with cornices hanging over them.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

A weak upper trough Tuesday should deliver a trace of snow and a shot of wind. A vigorous low makes landfall on Wednesday which has potential to bring significant precipitation. Unfortunately the weather models have not yet agreed on a solution with regard to track and intensity, but there will likely be less uncertainty as we get closer to Wednesday. Stay tuned for more details. TUESDAY: Broken cloud cover, freezing level around 750 m, moderate to strong west/northwest wind, 1 to 3 cm of snow.WEDNESDAY: Overcast, freezing level around 750 m, potentially strong to extreme south/southwest wind, latest model run shows about 10 cm of snow. Stay tuned for more details. THURSDAY: Scattered cloud cover, freezing level around 1000 m, light southeast wind, trace of snow possible.

Avalanche Summary

A lot of avalanche activity was reported on Sunday as the 25 to 40 cm of recent storm snow ran on the February 22nd weak layer. Control work produced numerous loose dry storm and wind slab avalanches to size 1.5 on a variety of aspects. A size 1.5 storm slab failed naturally on a steep roll on a northeast facing slope at 1600 m while a size 2.5 natural avalanche was reported from a southeast aspect of the Miller glacier at 2250 m.

Snowpack Summary

Storm totals from the weekend are between 25 and 55 cm. This snow was subject to strong to extreme winds out of the southeast, south and southwest on Sunday which formed fresh wind slabs that extend down to treeline. The new snow rests on the February 22nd interface which consists of old wind slabs, spotty surface hoar, facets and a sun crust on solar aspects. Recent testing has shown resistant planar shears at this interface which makes sense given the activity listed above. Beneath the February 22nd interface the snowpack is well settled and strong. Variable winds in the past month have produced cornices on all aspects. They will become touchier as they grow in size, as temperatures rise, and when they are subject to the strong late-winter sun on clear days.

Problems

Wind Slabs

Strong wind has formed wind slabs that may remain sensitive to human triggering and west/northwest wind Tuesday will likely create fresh wind slabs. Seek out wind sheltered terrain where you can avoid wind slabs and find the best riding conditions.

Avoid both lee and cross loaded slopes at treeline and in the alpine.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Cornices

Large cornices have formed along ridgelines. Cornices are inherently unstable, unpredictable, and demand respect, especially when the sun is out.

Give cornices a wide berth when traveling on or below ridges.Firm cornices may pull back into flat terrain at ridgetop if they fail.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Feb 27th, 2018 2:00PM