South Rockies

The recent snow is not sticking well to the crust and storm slabs will likely be reactive to human triggers at upper elevations on Thursday. 

High pressure will build off the coast today bringing dry and cooler conditions through the forecast period.

Thursday/ Friday: Mix of sun and cloud. Alpine temperatures near -5 with freezing levels falling to the valley. Ridgetop wind light from the East.

Saturday: Sunshine with some cloud. Alpine temperatures near -13 and ridgetop wind light from the southwest.

No new avalanche reports on Wednesday. 

The neighboring Lizard-Flathead region did report widespread natural and human triggered storm slab avalanches up to size 2, failing on the recent December 8th rain crust. I suspect this may be a similar story in this region where snow amounts in the 20 + cm range fell.

Have you been out? If so, we would love to hear about it on the Mountain Information Network. A picture is worth a thousand words! Thanks for your submissions. 

10-25 cm of new snow fell at upper elevations (the higher amounts in the Northern part of the region) while the rest of the precipitation came in as rain or freezing rain. Recent reports suggest that the freezing rain occurred from 1800m to 2000m “ish” with rain at lower elevations that likely destroyed most surface hoar. I also suspect very little surface hoar survived at higher elevations between the wind and the warming/sunshine last weekend, but maybe wind-sheltered pockets still exist? Depending on when and where the freezing levels started to drop in the past 24 hrs determines where that snow/rain line is. At lower elevations, it’s likely that a firm crust exists. At upper elevations, a reactive storm slab may exist, especially where the new snow sits above this recent rain/freezing rain crust, or the older melt-freeze crust found on solar aspects. Isolated pockets of stiff wind slab may exist on leeward slopes where the new snow deposits into deeper drifts. 

Digging deeper in the snowpack two predominant crusts exist from November. A widespread rain crust from early November that can be found up to 2500 m and buried down around 100 cm and a shallower one from late November down around 30 cm. These crusts have shown no recent reactivity in snowpack testing and this “potentially” problematic snowpack structure is not currently listed as an avalanche problem but remains on our radar moving forward.

The snowpack is generally thin, wind hammered, variable in wind-scoured areas, and tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are nearing 100 cm and beginning to exceed the threshold for avalanches.

• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• Closely monitor how the new snow is bonding to the crust.
• Recent new snow may be hiding windslabs that were easily visible before the snow fell.
• A crust on the surface will help bind the snow together, but may make for tough travel conditions.