Avalanche Forecast

Issued: Jan 14th, 2013 10:06AM

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

ghelgeson, Avalanche Canada

South Rockies.

I’ve gone with the GEM global solution that shows a big warm up, thus this forecast is based on rapidly increasing temperatures. If it doesn’t warm up, then these danger ratings are one notch too high. See the forecasters blog for warming details.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

The models can’t decide whether or not warm air will make its way into this corner of the province. I’ve gone with the GEM global solution that shows a big warm up, thus this forecast is based on rapidly increasing temperatures. Tuesday: Winds out of the NW at extreme values. Freezing level rising to 2500m+ around lunch time. No snow/rain. Clearing skies.Wednesday: Freezing level stays high around 2300m. Strong/Extreme NW winds persist. No precip expected.Thursday: Freezing level comes down to 2000m. Winds switch to westerly strong. Increasing to westerly extreme in the afternoon.

Avalanche Summary

No new significant avalanche observations, just a bit of surface sluffing.

Snowpack Summary

Thin 1F wind slab 5 - 10 cm thick formed Sunday, hasn't been very reactive. Below this around 60cm of settled snow rests on a myriad of old surfaces (January 4th interface) that include sun crust on steep south and west facing terrain, surface hoar in sheltered locations at treeline and below and facets everywhere else. The bond at this interface has tightened up and gained a lot of strength with the cold temps. The midpack is well settled and strong with one or two (location specific) crusts deep in the snowpack. These crust/facets combos are largely dormant, with the only concern being triggering from a shallow snowpack area or with a heavy trigger.

Problems

Wind Slabs

NW winds are forecasted to be screaming (extreme) at ridgetop. Watch for wind slab formation in exposed terrain in both the alpine and treeline vegetation bands.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

I suspect this layer will spring back to life when the warm temps and sunshine come out Tuesday. Slopes that didn't slide in the last cycle are of particular concern. Pull back to simple terrain without overhead hazard as soon as it warms up.

Avoid traveling on slopes which are becoming wet due to sun and warm temperatures.>As the sun comes out and the temperatures rise the potential for large avalanches failing on the buried surface hoar will quickly increase.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Jan 15th, 2013 2:00PM