Avalanche Forecast

Issued: Mar 26th, 2018 4:31PM

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

conrad janzen, Parks Canada

Banff Yoho Kootenay.

Things will start to get touchy as the new snow arrives with strong W winds. Minimize overhead hazard and avoid steep confined terrain until things have a chance to settle. Sheltered areas at lower elevations may provide the best skiing.

Summary

Weather Forecast

Temperatures will remain below freezing on Tuesday as 10 to 20 cm of new snow arrives with moderate to strong west winds. Precipitation will drop off on Wednesday but expect the winds to remain in the moderate to strong range for the next few days.

Snowpack Summary

Moderate to strong SW winds are creating wind slabs in alpine and treeline areas and beginning to over load cornices. 10-20 cm of recent snow sits over a melt freeze crust on solar aspects with some facets at the crust interface. In shallow snowpack areas the basal facets remain quite weak and may be susceptible to triggering with large loads.

Avalanche Summary

Three size 2-2.5 natural cornice triggered avalanches were observed today with crowns ranging from 20 to 120 cm deep. Two were observed on Helen Ridge and one was seen on Jimmy Junior near Mt Jimmy Simpson. Some whumphing on the buried crust from March 15 was also experienced in the Cirque Peak area.

Confidence

Intensity of incoming weather systems is uncertain on Tuesday

Problems

Wind Slabs

Wind slabs and wind effect will increase on Tuesday with the arrival of new snow and continued W winds. We expect to see increased natural avalanche activity, especially as cornices get over loaded and fail, and human triggering will be likely.

Pay attention to overhead hazards like cornices which could trigger slabs.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Persistent Slabs

As the new snow increases the load over the March 15 crust on solar aspects we may start to see avalanche activity on this layer. If the facets below the crust also fail, larger propagations will be possible.

Watch for signs of instability such as whumpfing, or cracking. The recent snow may be more sensitive to human triggering on solar aspects where it sits on sun crust

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2.5

Valid until: Mar 27th, 2018 4:00PM