Avalanche Forecast

Issued: Apr 4th, 2013 4:19PM

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

rupert wedgwood, Parks Canada

Jasper.

Up to 20cm of new snow has been forecast over the next 24 hours. There will be good skiing in sheltered treeline locations.

Summary

Weather Forecast

Starting this evening light rainfall will transition into snow. Amounts will be greatest at upper elevations where over the next 24 hours 20cm may fall.Â Winds willÂ be light out of the NE at lower elevations and moderate SW near ridge tops gusting strong. The overnight temperatures may not allow for good crust formation at mid treeline elevations.

Snowpack Summary

Below Treeline a supportive 15cm melt freeze crust provides temporary stability above a wet and unconsolidated snowpack. The crust thins with elevation and on slopes which are not South facing. By mid afternoon, or earlier on very hot days, this crust will melt and the avalanche danger will elevate considerably. The base of the snowpack is weak.

Avalanche Summary

Evening rain may see a short lived spike in wet avalanches at lower elevations this evening. The falling temperatures will put a stop to this as the rain transitions to snow. Ridge top winds will produce soft slabs with the new snow and where this happens to fall on an established melt freeze crust bonding will likely be poor, at least initially.

Confidence

Track of incoming weather systems is uncertain

Problems

Storm Slabs

With up to 20cm of new snow due tonight and tomorrow along with moderate SW winds we are anticipating soft storm slabs to be forming at upper elevations. Slab bonding is expected to be touchy on the current sun and temperature crusts.

The new snow will require several days to settle and stabilize.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

These heavy and unstable features can fall unexpectedly triggering deep large avalanches. With snow and SW winds forecast the significants and impact of these features should not be overlooked.

Extra caution needed around cornices with current conditions.Avoid steep slopes below cornices.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Loose Wet

Cooling temperatures have reduced the magnitude, frequency and distribution of these events. Pay close attention to the increasing air temperature and the thickness of the melt freeze crust. Rain events will increase the elevation range and aspect.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Travel early on frozen crusts before the heat of the day.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 5th, 2013 4:00PM