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Parks Canada jesse milner, Parks Canada

Jasper National Park Avalanche Forecast

May 11th, 2019 4:00PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Loose Wet, Persistent Slabs and Cornices.

To freeze or not to freeze...

Summary

Weather Forecast

Warm and convective with no overnight freezes.

Sunday: Cloudy, 2800m freezing levels and possible showers starting in the evening. Light ridge wind.

Monday: Cloudy with showers, up to 6mm Low 2, High 9. Freezing levels 3000m. Light ridge wind.

Tuesday: Cloudy with scattered showers up to 4mm. Low 3 High 10 light-moderate winds. Freezing level 3100m

Snowpack Summary

Snowpack is becoming isothermal into the alpine on shady aspects. The snowpack has transitioned rapidly from winter to a summer like snowpack. Little to no overnight freezes are forecasted.

Avalanche Summary

Since the warming trend there has been an avalanche cycle. Numerous loose wet avalanches up to size 2 have been observed in the alpine and treeline. Near Jasper townsite in shallow snowpack areas several large (size 3) slab avalanches have been observed on North to Easterly aspects in the alpine and running into valley bottoms.

Confidence

Freezing levels are uncertain

Problems

Loose Wet

An icon showing Loose Wet

Likelihood

Very Likely - Likely

Expected Size

1 - 2

Summer like temps have created an avalanche cycle. With no overnight freezes and more sunny days forecasted this problem will continue for the next while. Limited snow below treeline but one could expect it to be very isothermal and reactive.

  • If triggered loose wet sluffs may step down to deeper layers resulting in larger avalanches.

Aspects:

All aspects.

Elevations:

All elevations.

Persistent Slabs

An icon showing Persistent Slabs

Likelihood

Likely - Possible

Expected Size

1.5 - 3

Weak mid-pack facets and upper-snowpack are reactive, especially on shaded, wind-sheltered slopes. This is a Wet Slab problem on solar aspects, as water accumulates above strong crusts.

  • Minimize exposure to big slopes, especially during the heat of the day.
  • If off-trail travel is deep and punchy, avoid all avalanche terrain, including runouts.

Aspects:

All aspects.

Elevations:

Alpine, Treeline.

Cornices

An icon showing Cornices

Likelihood

Possible

Expected Size

2 - 3.5

Occasional cornice falls are expected, increasing into the weekend. some of these may trigger large slab avalanches, running well down into lower elevations.

  • Stay well to the windward side of corniced ridges.
  • Minimize exposure to overhead hazard from cornices.

Aspects:

North, North East, East, North West.

Elevations:

Alpine, Treeline.

Valid until: May 12th, 2019 4:00PM