Avalanche Forecast

Issued: Feb 29th, 2012 9:30AM

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

ghelgeson, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Freezing levels are uncertain on Saturday

Weather Forecast

THUR: A dirty ridge hangs over much of the region today bringing cloudy skies and the occasional convective flurry. I'm only expecting a few cm's Thursday, even in the most favored valleys. The atmosphere stabilizes Thursday evening & 2000m temps drop down to - 16 overnight. FRI: Friday dawns cool & cloudy, but, it is a day of change in the pattern. The ridge flattens late in the day Friday, which turns the firehose on for most of the province, but, the So. Rockies largely miss out on the precip. WEEKEND: Expect a few cm each day Friday, Saturday & Sunday. Freezing levels will be on the rise each day too: Fri: 1000m, Saturday 1500m & Sunday 2000m. The models show a Chinook shaping up for the region on Sunday as well. 2000m Wind: Thur: L, WFri: High End of Mod, West switching to NW and increasing to Strong 2nd half of day.Sat: Strong, NWSun: Strong to Extreme, W

Avalanche Summary

Our field team observed an avalanche failing on a steep bluff Tuesday, the SH was assumed to be the weak layer. No other reports of avalanches from this region, but that doesn't mean they aren't happening. It's important to remember that this region is often quite data sparse.

Snowpack Summary

Saturday night into Sunday, moisture in the west of the region collided with cold air in the east and resulted in an intense period of heavy snowfall that was very low density. This new snow has likely settled a bit with daytime warming Monday. Now 50-60 cm of recent snow sits on a reactive weak layer of crusts, surface hoar and facets.Our field team was in the Elk Valley North sub region, operating between 2000 & 2300m on Tuesday. They reported weaknesses failing with moderate to hard shears down 60 cm. It will be interesting to see what kind of results they get from their field days in the next 72 hours. For the moment, we can assume that there is a slab of approx. 60 cm in depth in most of the region that is still prone to human triggering.Below this, the mid-pack is quite strong in most locations. However, lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones.

Problems

Wind Slabs

Fresh wind slabs will probably be created Wednesday evening as SW winds go to work on the new snow. These will likely be quite reactive to skiers and riders Thursday with the potential to create large (Size 2) avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Loose Dry

Light dry snow that fell over the past few days has been sluffing in steep terrain, running far and fast. Wednesday evenings 5 - 10cm of storm snow will likely react in a similar fashion in wind sheltered terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

While the slab resting on the Feb. 08 SH has grown more stubborn, this layer is still prone to human triggering & avalanches failing on this layer, now down an avg. of 60 cm, will be large and destructive.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 6

Valid until: Mar 2nd, 2012 8:00AM