Avalanche Forecast

Issued: Mar 4th, 2012 9:02AM

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

ghelgeson, Avalanche Canada

South Rockies.

Summary

Confidence

Fair

Weather Forecast

The South Rockies see a bit of snow during this forecast period as a surface low develops over the southern interior and subsequently exits to the SE Monday evening. Light snow should begin Sunday around midnight delivering just a few cm overnight. Snow continues through the day Monday cooling as the day progresses. I expect 10 – 20 cm before skies clear Tuesday morning. Tuesday dawns clear and cold setting the stage for a spectacular day in the mountains.FZLVL:Mon: Starts near 2000m, lowering to the surface by Tuesday AMTue: SurfaceWed: Starting near the surface, rising as high as 1600 in the afternoon, returning to the surface overnight.Wind: Mon: 2km: Mod/Strong SW, Strong to Extreme SW at ridgetop. Diminishing overnight.Tue: L, NE at all elevations.Wed: 2km: Mod W/NW, ridgetop winds mod/str NW.

Avalanche Summary

Our field team remoted a size 2 avalanche from the flats Wednesday. It's worth checking out the details of the incident report linked to this forecast as it illustrates just how tender the persistent slab problem is in the So. Rockies. On Saturday a group of sledders remote triggered a size 1.5 avalanche which failed on the Feb.09 SH in the Coal Creek area on a North facing, 37 degree slope at 1600m.

Snowpack Summary

Strong winds and have formed wind slabs up to 20 cm deep in wind exposed terrain at and above treeline as of Sunday afternoon. The Feb. 09 surface hoar is now down between 40 & 90 cm. The depth varies throughout the region. This weak layer continue to perform, our head field technician was out for a ski and noticed a remote triggered avalanche on Saturday. See the details below. Snowpack tests continue to show sudden moderate failures on this interface. This weekend the upper snowpack is changing character as strong to extreme winds at ridge top & mild temperatures form the old storm snow into a more cohesive slab. Lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones.Our field team was out in the Crowsnest Thursday where they observed a much stronger snowpack. The So. Rockies forecast is intended to give trends for the region as a whole, and as such, conditions will vary between the different sub regions.

Problems

Persistent Slabs

Persistently weak buried surface hoar demands continued diligence and conservative decisions. The potential for remote triggering, step down avalanches, and wide propagations, makes this weakness particularly tricky to predict.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Wind Slabs

Generally lurking below ridgecrests, behind terrain breaks, and in gullies. Fresh wind slabs fueled by new snow are expected to be touchy. Continued strong winds Monday may overload buried weaknesses.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

Watch for sensitive storm slabs as snow totals begin to stack up Monday afternoon. These should be shallow (10cm+) in depth and relatively easy to manage.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Mar 5th, 2012 8:00AM