Avalanche Forecast

Issued: Mar 20th, 2013 9:20AM

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

Avalanche Canada pmarshall, Avalanche Canada

Snowfall amounts are uncertain. If there's heavy snowfall in your area, the local avalanche danger may be higher than forecasted.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday

Weather Forecast

Synopsis: A strong low pressure system today with wind and mild temperatures is followed by a cool and unsettled air mass through Friday. Conditions will become gradually less windy and less convective but stay generally cooler than normal for the period. Saturday and Sunday the cool north/northwesterly flow will dry out as a ridge of high pressure is very slowly approaching the regions.Wednesday Night: Freezing Level: Valley Bottom. Precip: 10/15mm – 10/25cm Wind: Strong NWThursday: Freezing Level: Valley Bottom. Precip: 2/4mm – 4/10cm Wind: Moderate W gusting Strong/Extreme NW Friday: Freezing Level: Valley Bottom. Precip: 2/4mm – 4/10cm Wind: Light gusting strong NorthSaturday: Freezing Level: 800m No significant precip expected.  Wind: Light, SW

Avalanche Summary

On Tuesday a few natural soft slabs were observed that were thought to have occurred in the last 48 hours.  Cornice fall to size 1.5 was observed in the Fernie area but the falling chunks of cornice did not initiate avalanches.

Snowpack Summary

As of Wednesday afternoon the storm had yet to impact the South Rockies, but, I suspect it will still deliver a good shot of snow and wind this evening.  New storm slabs are likely to develop Wednesday night into Thursday. Wind-loaded slopes and spill zones (fans where snow accumulates below steep faces) may be particularly touchy. A buried rain crust may provide an easy sliding surface for avalanches. This crust is supportive to at least 2100 m in most areas and is up to 9 cm thick. It's thought to be strong enough that snowpack weaknesses below it wont be affected by the load of a person, with the caveat that there may be isolated exceptions (e.g. thin spots near rocks at high elevations). The mid-pack is generally well-settled. Cornices are large and fragile in some areas.

Problems

Storm Slabs

An icon showing Storm Slabs
New storm slabs may develop Wednesday night into Thursday. Lee loaded slopes and spill zones may be particularly touchy. A buried crust may provide an easy sliding surface for avalanches.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid freshly wind loaded features.>Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Mar 21st, 2013 2:00PM