Avalanche Forecast

Issued: Apr 22nd, 2013 4:00PM

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

rupert wedgwood, Parks Canada

Jasper.

Solar radiation and day time heating will rapidly and dramatically increase the avalanche danger. Pay close attention to the effects of sun on the snowpack as the afternoon approaches. Start your trip early and finish early if its a warm afternoon.

Summary

Weather Forecast

Cool air from the north will remain over the area on Tuesday with the possibility of up to 5cm of fresh show. The greatest snowfall is forecast to occur to the east and at upper elevations. Moderate ridge top winds from the N and NW will redistribute the snow onto southerly and easterly facing slopes. Temps at treeline will approach zero in mid PM.

Snowpack Summary

A spring temperature crust up to 15cm thick can be found near the top of the snowpack. This crust has been found as high as 2600m in the Icefields area. In places it is buried under several inches of new snow. Wind slabs can be found at upper elevations on most aspects due to varied wind direction patterns. Cornices are large and dropping.

Avalanche Summary

No new avalanches were reported today. One avalanche was reported late Friday above the icefalls on the Athabasca glacier which originated from steep, cross loaded gullies in the high alpine. Cooler temperatures and no solar radiation due to cloud cover has reduced natural activity in the last few days.

Confidence

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

Problems

Wind Slabs

Isolated pockets of wind slab can be found on lee aspects in exposed alpine terrain near ridge crests. Expect to encounter this condition on NW and SW aspects due to variable wind directions over the past week.

Avoid travelling in areas that have been reverse loaded by winds.Avoid traveling on ledges and cliffs where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Wet

Freezing temperatures overnight will produce a good melt freeze crust keeping the danger low for much the morning. Solar aspect, late in the day, are the most at risk from this avalanche hazard.

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, South East, South.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Cornices

It is that time in the spring when warmer daytime temperatures combined with milder overnight temperatures will make cornices more susceptible to collapsing. They seem larger this year and may still trigger deep instabilities on north aspects.

Avoid steep slopes below cornices.Cornices become weak with daytime heating, so travel early on exposed slopes.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 23rd, 2013 4:00PM