Avalanche Forecast

Issued: Apr 3rd, 2013 4:06PM

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

rupert wedgwood, Parks Canada

Jasper.

If the forecast precipitation falls as rain rather snow expect the avalanche danger to rise rapidly at low elevations.Road closures after mid day along the Maligne Lake Road and Icefields Parkway can be expected if we see significant rain.

Summary

Weather Forecast

A possibility of light rain at lower elevations and snow near treeline. Up to 30cm of new snow could fall by Saturday evening as cool easterly air is confronted by an upper elevation westerly flow. Valley bottom temperatures will warm during the day producing convective uplift and more snow. Glacial out flow will cool the valleys overnight.

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 increase considerably. The base of the snowpack is weak.

Avalanche Summary

Avalanche activity will be at its greatest by mid afternoon or during rain events. During the morning a strong crust prevents natural avalanches. As the crust melts the danger increases. At that time avalanches up to size 2 can be expected. Falling cornices can trigger full snowpack slabs of size 3 from the alpine. Cool temps reduce the danger.

Confidence

Freezing levels are uncertain

Problems

Cornices

These heavy and unstable features can fall unexpectedly triggering deep large avalanches. These are commonly, but not exclusively, found above east facing slopes at ridge top elevations.

Extra caution needed around cornices with current conditions.Give cornices a wide berth when travelling on or below ridges.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Loose Wet

Cooling temperatures over the next 3 days will reduce magnitude, frequency and distribution of these events. Pay close attention to the increasing air temperature and met freeze crust thickness. When crusts are gone you should head for safer slopes.

Start and finish early before the surface crusts melt.Sluffs may trigger deeper instabilities.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Wet Slabs

These events have been observed up to 2600m on south facing slopes. Cool temps over the next few days will reduce the magnitude and distribution. These events are most likely in the afternoon when the sun is out or during periods of significant rain.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Avoid shallow snowpack areas where triggering is more likely.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

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