Avalanche Forecast

Issued: Dec 6th, 2017 4:00PM

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

rupert wedgwood, Parks Canada

Jasper.

Warm temperatures and freezing levels to 3,500m will increase the avalanche danger at all elevations.

Summary

Weather Forecast

Thursdays freezing levels are forecasted to spike to 3,500m with alpine highs of +5 C. The effect of the temperature on the snowpack and rock faces will be increased with direct solar radiation. The avalanche danger is expected to increase as this occurs. Ridge wind NW10-20 km/h. Cooling will take place on Friday and Saturday.

Snowpack Summary

The snowpack is well settled. Wind slabs are in exposed lee features at and above treeline. A significant crust (Nov.23) can be found down 30 to 70cms. A persistent slab overlays this crust and so far the bond appears to be strengthening at this interface. The Halloween crust sits well down in the snowpack at TL locations and as high as 2700m.

Avalanche Summary

No new avalanches have been observed or reported on Wednesday. The high freezing levels on Thur is expected to wake up the weaknesses within the snowpack. Small snowballs and sections of falling cornice may trigger deeper instabilities producing large avalanches. Solar facing avalanche terrain should be avoided at treeline and above.

Confidence

The weather pattern is stable on Thursday

Problems

Deep Persistent Slabs

Although this deeply buried crust, on which this weakness beds, is widespread we think that it will be at its most reactive on solar facing slopes. Thursdays weather is abnormally warm and its effect on the snowpack will be to destabilize it.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

Wind slabs are present on lee aspects. Bond strength of these slabs to the snowpack below is uncertain. The warm temperatures on Thursday will likely trigger avalanches which will step down to deeper layers in the snowpack

Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Dec 7th, 2017 4:00PM