Avalanche Forecast

Issued: Mar 5th, 2012 10:13AM

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 - Due to limited field observations

Weather Forecast

The South Rockies should see 10 -15 cm during the day Monday and another 10 cm Monday night. Tuesday starts out cloudy & cold accompanied by light N/NE winds, there may be the occasional sunny break in the afternoon. The freezing level should stay near the surface Tuesday. On Wednesday warm air floods the region, as a result freezing levels climb to 1700m. Winds should be moderate out of the W at treeline Wednesday, Strong out of the NW at ridgetop. Thursday looks to be the warmest day with the freezing level climbing to 2500m in the afternoon. The models currently show a 3000m freezing level on Friday.

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

10cm of new snow fell during the day Monday & another 10 cm is expected Monday night along with strong NW winds. 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. The weekends strong winds and mild temperatures formed the upper snowpack into a more cohesive slab. Our field team will be out Tuesday so we should have a better handle on the upper snowpack later in the week. 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 night may overload buried weaknesses.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Storm Slabs

New snow should bond well to the old snow surface, but be careful with convex rollers and unsupported slopes where the chances of triggering an avalanche are increased.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Mar 7th, 2012 8:00AM