Avalanche Forecast

Issued: Mar 28th, 2013 8:00AM

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

Parks Canada sylvia forest, Parks Canada

Cornices and daytime heating remain the primary concern today.  Watch for changing snow conditions throughout the day, and with changes in aspect and elevation.  Even small moist sluffs could bury a person.

Summary

Weather Forecast

Clear skies will be replaced by a small disturbance today, bringing partial cloudiness for part of the day.  An upper ridge will re-build again tonight.  The long weekend looks mostly sunny and clear, with warm temperatures and elevated freezing levels.  Minimal or no precipitation, and light winds are expected.

Snowpack Summary

The generally well settled snowpack is being affected by strong solar radiation.  North aspects are remaining cool, but sunny aspects and all lower elevations are warming up substantially during the day.  Thin snowpack areas will be most susceptible, specifically on S and W aspects.  Several PWLs (mostly buried sun crusts with SH) are still active.

Avalanche Summary

Numerous moist avalanches were reported yesterday from Asulkan and Connaught, and along the highway corridor.  Most of these are scrubbing the surface snow, but a few are digging into deeper layers.  Cornice triggered avalanches have increased throughout the area, with warm daytime temperatures, some of which broke down to deep PWL's.

Confidence

The weather pattern is stable

Problems

Cornices

An icon showing Cornices
Cornices are large and unsupported. Wide fluctuations in diurnal temperatures are increasing their fragility and very warm afternoon temps will make them weaker.  Cornice triggered large avalanches are possible. 
Cornices become weak with daytime heating.Give cornices a wide berth when travelling on or below ridges.

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

An icon showing Persistent Slabs
PWL's are becoming stubborn, but should not be discounted.  Slopes receiving direct sun become more reactive during the day with warming. This is most likely on steep solar aspects where buried crusts exist, but northerly aspects are not immune.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.Be aware of thin areas that may propogate to deeper instabilites.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Wet

An icon showing Loose Wet
The sun will be strong today.  Avoid terrain traps where moist slides could pile up deeply.  Solar triggered avalanches are most likely around exposed rocks and may trigger deeper slabs.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Valid until: Mar 29th, 2013 8:00AM