Avalanche Forecast

Issued: Apr 4th, 2016 8:26AM

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

pmarshall, Avalanche Canada

South Columbia.

Fresh snow, and potentially a fresh wind slab problem, await you if you manage to get up high in the mountains on Tuesday. However, this brief change gives way to another heat wave later in the week.

Summary

Confidence

High

Weather Forecast

TUESDAY: Mainly cloudy with a chance of showers/flurries and afternoon sunny breaks. The freezing level dips to around 1400 m overnight and rises to 1500-1600 m during the day. Winds are moderate to strong from the West. WEDNESDAY: Clearing. The freezing climbs to 2500 m and winds are light to moderate from the West. THURSDAY: Mainly sunny. The freezing level continues its ascent up to 3000 m. Winds should ease to light and variable.

Avalanche Summary

Recent soaring temperatures and strong sunshine have resulted in significant natural avalanche activity for the past several days. Slab avalanches to size 2.5 have been very common over the last few days on almost all aspects (the exception being high elevation north). Large loose wet avalanches and cornice falls have also been a common theme. Cloud cover and slight cooling might halt natural activity briefly this week.

Snowpack Summary

Recent warm temperatures, weak/non-existent overnight refreeze, and rain have moistened the upper snowpack at all elevations. Elevations above 2000 m may getting snow on Monday (10-15 cm is possible), and a cooling trend could create a crust at or near the surface down to around 1500 m. Below 1400 m, the snowpack is likely fully isothermal. The March 22nd rain crust is present to around 2000 m, but the warm temps have likely allowed the overlying 40 to 50 cm of snow to bond well. Once it freezes, this layer should not be much of a concern. The late February persistent weak layer is now down 60 to 120 cm below the surface. While it may be a concern in isolated terrain, it would probably take a large trigger like a cornice fall or surface avalanche in motion to provoke it.

Problems

Persistent Slabs

Brief and slight cooling on Tuesday could make this problem less sensitive to triggering, but keep this on your radar for later in the week when the heat and sun return.

A buried persistent weak layer (PWL) is lurking in our snowpack which means there is potential for large destructive avalanches that have the capability to run full path.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Wind Slabs

New snow and strong winds on Monday could combine to build fresh and touchy wind slabs in exposed leeward terrain. Expect any new snow to sluff off easily if the sun pokes out at all.

Be alert to conditions that change with elevation.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Cornices

Cooler temperatures and more cloud might make cornices less likely to fail naturally, but I would still give droopy overhanging cornices a wide berth.

Do your best to avoid traveling on or underneath cornices. If you have to, move quickly and only expose one person at a time.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 5th, 2016 2:00PM