Avalanche Forecast Banff Yoho & Kootenay National Park

Friday 1st February 2019

Avalanche Danger Ratings Fri 1st Feb 4:20PM Danger Ratings Alpine: Considerable Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Moderate Storm Slabs Storm Slabs Deep Persistent Slabs Deep Persistent Slabs

Parks Canada Forecaster: conrad janzen

Date Issued:

Valid Until:

The avalanche hazard will rise overnight and into Saturday with additional snow and wind. Northern areas will receive the greatest amounts. Stick to more conservative lines and avoid steep overhead terrain until the new snow has a chance to bond.

Weather Forecast

Snow through Saturday with forecast amounts from 10-25 cm at treeline. Northern areas will see the highest amounts. Winds remain in the moderate range with strong gusts out of the SE to SW depending on how the cold front behaves.  Temperatures remain in the -5 to -15 range before plummeting Saturday night. Flurries and very cold temps on Sunday.

Snowpack Summary

15-25 cm of new snow with moderate SW-SE winds is building slabs in lee areas of the alpine. The mid-pack is quite dense above the Dec 10 interface down 70-140 cm. In shallower snowpack areas weak facets exist below the Dec 10 interface, with moderate-hard test results in the facets. In deeper snowpack this basal weaknesses is less pronounced

Avalanche Summary

Local ski hills reported ski cutting small loose dry and wind slabs up to size 1.5 on Friday in steep lee areas. No reports or avalanche observations from the back-country, but we expect an increase in avalanche activity over the next 36 hrs.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Saturday

Storm Slabs Storm Slabs

Likelihood

Likely

Expected Size

1 - 2

We expect 20-40 cm of storm snow by Sunday with moderate-strong SW-SE winds. Storm slabs will form in many areas. Natural avalanches are expected in extreme terrain and human triggering will be likely in deeper storm snow or wind loaded areas.

Use caution in lee areas in the alpine and treeline. Storm snow is forming reactive slabs.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

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Deep Persistent Slabs Deep Persistent Slabs

Likelihood

Possible

Expected Size

1 - 3

The new snow load may start waking up the Dec 10th deep persistent facet weakness down 60-140 cm. This is of greatest  concern in shallow snowpack areas where the basal facets are weakest.

Avoid thin, rocky or unsupported slopes.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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