Avalanche Forecast

Issued: May 2nd, 2014 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Deep Persistent Slabs, Loose Wet and Wind Slabs.

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Winter is back at the higher elevations with cooling temperatures and 5-10cm of new snow forecast for each of the next few days. Watch carefully for rising temperatures as any increase in freezing levels will result in an increased danger rating.

Summary

Weather Forecast

Light North winds with periods of snow and accumulations between 5-10cm are expected over the next three days. Alpine temperatures will drop to between around -5'C to -10'C overnight with day time highs hovering at or just above the freezing level. Freezing levels are forecast to remain near the 1900m level.

Snowpack Summary

Rain to tree line this morning followed by 5-10cm of wet snow with greater accumulations in the alpine. Below tree line the snowpack is mostly isothermal and rain soaked. Thin areas at tree line and above are also becoming isothermal. Avalanches are occurring on the the deep persistent weak layers of facets and depth hoar during this warm spell.

Avalanche Summary

Numerous loose wet slides to size 2.5 and deep slab avalanches to size 3 failing on the basal facets have been observed over the past 24 hours on all aspects and at all elevations. The majority of the deep slabs are occurring in thin steep rocky ground in the alpine. Several recent cornice failures up to size 2 have also been observed.

Confidence

Freezing levels are uncertain

Problems

Deep Persistent Slabs

As temperatures cool in the alpine the likelihood of triggering the deep facets layers will decrease. Tree line areas received the most rain and will take longer to cool down and heal. Avoid exposure to large avalanche paths until this cycle is over.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

This will be most prominent at lower elevations and on any solar aspects with daytime warming. Travel early when things are cool and avoid traveling in avalanche terrain later in the day.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Wind Slabs

The new moist snow will form small storm slabs and wind slabs in the alpine. This will settle out quickly but use caution in steep terrain until things cool down and the new snow has a chance to bond.

The new snow will require several days to settle and stabilize.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: May 3rd, 2014 4:00PM