Avalanche Forecast

Issued: Apr 8th, 2012 10:17AM

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

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Monday is the tail end of the beautiful weather pattern we've been in for the past few days. The upper flow switches from northerly to a more mild southerly on Tuesday which will push freezing levels above 3000 m. Monday: Freezing level starts near the surface, topping out around 2000m. A few clouds build into the region in the afternoon. The current forecast shows that Monday night is the last good overnight refreeze until next weekend. Tuesday: Temperatures should already be near 2000 m at dawn and are forecasted to continue to climb to 3000 m by lunch time. Cloud cover increases to 50% as winds blow at light values out of the east below treeline. At ridge top expect moderate southeasterlies. Temps remain high through the night. Wednesday: Freezing level stays around 3000 all day. Ridge top winds moderate SE diminishing in speed at lower elevations.

Avalanche Summary

Last week's storm snow is now fairly well settled which has scaled avalanche activity way back. The only avalanche activity reported Saturday was from a high elevation NW facing slope that failed naturally producing a size 2.5 avalanche.

Snowpack Summary

Mild temperatures continue to drive rapid settlement of last week's storm snow. A sun crust is in place on slopes that face SW, S & SE. Dry snow can be found on due north facing slopes down to around 1400m. Around 30 cm of snow fell Wednesday accompanied by moderate southwest winds which brings total snowfall since March 26th to 120 cm. This snow rests on a suncrust on solar aspects and a melt freeze crust on non solar aspects below 2000m. The March 26 interface consists of a melt/freeze crust down around 100cm, on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond at this interface is gaining strength, with lingering concerns on true south aspects where the crust is thickest and where the surface hoar lurks. At lower elevations, the consistent high freezing levels have kept the new snow heavy and moist. The persistent early February surface hoar lingers deep in the snowpack and may once again become a player mid-week when the region goes several days without a good overnight refreeze or recovery. Concern remains with heavy triggers (cornice), step down avalanches and rapid loading from intense precipitation, strong winds or sun.

Problems

Loose Wet

An icon showing Loose Wet
Intermittent strong sun is forecast for Monday as convective clouds and the sun dance through the sky. Watch for loose snow avalanches, with the potential for deeper slab avalanches on slopes that bake all day under the strong spring sun.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
Two layers to watch: April 3rd, down 30 cm & Mar. 26, down 100 cm. I'd be wary of triggering the deeper layer on steep unsupported slopes, especially in places where the snowpack goes from thick to thin; near ridge crests and rock outcroppings.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Cornices

An icon showing Cornices
Cornices have grown large & unruly. Cornices receiving direct sun will eventually grow weak & there is potential for cornice fall to initiate deep persistent slab avalanches on underlying slopes. Pay attention to what's happening above you.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 7

Valid until: Apr 9th, 2012 9:00AM