Avalanche Forecast

Issued: Jan 12th, 2018 4:00PM

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

tim haggarty, Parks Canada

Jasper.

Be on your game for the weekend. Persistent slabs in exposed areas make it difficult to travel with confidence. Watch for increasing west winds that may further develop windslabs and rising temperatures that may allow for easier triggering.

Summary

Weather Forecast

A ridge will reach the coast Friday and bring warmer, moist air to the Jasper region through the weekend. Alpine temperatures will be inverted and reach -6C on Saturday with a chance of a few flurries in the AM, watch for West winds to increase to 15km/h. An increase in the freezing levels to 2200m is called for Sunday as West winds to 20km/h.

Snowpack Summary

10-15cm of recent snow has blown into thin windslabs TL and above. Old slabs 10-30cm deeper sit on a weak layer of facets or surface hoar TL and above. In sheltered areas this new snow sits a faceted upper snowpack at all elevations. A strong mid snowpack crust is providing strength but is weakening. The lower snowpack continues to lose strength.

Avalanche Summary

Yesterday, besides a few small windslabs and sluffs from alpine terrain, a sz 2 slab 20cm deep and 50m wide likely failed on the Dec 18 persistent layer. This shallow slab ran a few meters before stepping down another 40 cm (likely through weak facets to the November 27 midpack crust). All of this ran 70m to a cliff triggering a small slab below.

Confidence

Due to the number of field observations on Friday

Problems

Persistent Slabs

New snow covers pockets of old slab sitting on weak, faceted snow that lacks strength, and may fail, to mid-pack depths. Treat all wind exposed areas with care but approach larger, uniform features and thin areas with caution.

Avoid shallow snowpack areas where triggering is more likely.Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

The new snow has already formed thin, spotty slabs even with the limited amount of wind we have seen so far. These slabs sit on freshly buried, weak facets and surface hoar in some areas. Watch for these slabs to develop with more wind Saturday.

Watch for surface cracking and stiffer surface layers of snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Dry

New snow covers a facetted/weak upper snowpack in sheltered areas. Be cautious in very steep terrain and in confined features where a small sluff could build mass. Even light winds were triggering these events along alpine ridges Thursday.

Use caution above ledges and cliffs where small avalanches may have severe consequences.The shallow, weakening snowpack makes for difficult trail breaking at low elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 13th, 2018 4:00PM