Avalanche Forecast

Issued: Feb 23rd, 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 and Wind Slabs.

tim haggarty, Parks Canada

Jasper.

A firm slab, sitting over several persistent weak layers, is found throughout the forecast region and remains a high consequence concern for human triggering. Continue to travel conservatively especially in the low alpine and around treeline areas.

Summary

Weather Forecast

A series of minor disturbances are tracking N- S against the west side of the Rockies through midweek. One of these systems is passing Friday, the next Saturday night. Small amounts of precip, temps rising to -10 at treeline Saturday and Sunday and increased westerly winds are likely. Cooling again on Monday before another system slides past.

Snowpack Summary

Previous Strong winds from W and N directions have left wind slabs and wind effect in open areas. The upper snowpack has settled to form a cohesive stiff slab that is sitting on three persistent weak layers mid-pack (down 50 to 80cm) which can be found throughout the forecast region, and have produced many large avalanches that have run full path.

Avalanche Summary

Minimal evidence of recent activity exists: mainly small windslabs in the S and W facing alpine. Widespread wind effect is evident. An extensive cycle was seen as the persistent slab became overloaded with successive storms. Avalanches to sz 3.5 were observed from most aspects and most elevations with the majority of the action seen around 21-2500m

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Persistent Slabs

A stiff slab 50 to 80cm thick, sits over: Sun Crusts (south and west aspects), Surface Hoar (at, and just above treeline) and weak Faceted Crystals (very developed in shallow snowpack features) This is a dangerous problem that is difficult to avoid.

Use conservative route selection, stick to supported terrain features, avoid overhead hazards.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3.5

Wind Slabs

Expect hardslabs in the alpine and a few softer slabs at treeline. The cold has kept these in check and helped these settle well over the last few days but some caution is still warranted with the expected warming and increased wind this weekend.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.The best powder will be found in sheltered locations at or below treeline.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 24th, 2018 4:00PM