Avalanche Forecast

Low - Timing, track, or intensity of incoming weather system is uncertain

Clashing fronts make the next few days difficult to forecast. A Pacific warm front and an Arctic cold front are converging over the Rockies, creating the potential for surprise accumulations of low density snow. Timing, location, and intensity are highly uncertain (and so are the snowfall estimates).FRIDAY: The first wave of snow starts Thursday night with 10-20 cm then another 5-15 cm possible throughout the day on Friday/ moderate west wind / alpine temperatures around -6 C.SATURDAY: Continued flurries with 5-20 cm possible / moderate west wind / alpine temperatures around -5 C.SUNDAY: Ongoing flurries with some possible sunny breaks / strong northwest wind / alpine temperatures around -3 C.

On Thursday, the fresh low density snow was reactive to ski cutting and produce small soft slab avalanches (20 cm thick) and dry loose avalanches in steep terrain. Some natural slab activity was observed in alpine terrain.Large deep persistent slab avalanches have been reported on a regular basis throughout January. On Tuesday, numerous large avalanches (size 2-3.5) were triggered naturally as well as with explosives. Many of the natural avalanches were triggered by cornices falling and releasing slabs on the December and November layers, producing 150-250 cm thick crowns. See the avalanche photos in this Mountain Information Network report for an example. The snowpack is still weak and additional stress (such as a cornice, person, or new snow) could trigger destructive persistent slab avalanches.

Expect waves of fresh snow over the next few days as storm snow accumulates. So far, about 40 cm of low density snow sits above a breakable crust up to 1700 m. Stay aware of the condition of the new snow. Mostly low density powder is expected, but could become heavy if it warms up. Also watch for slab development in wind affected areas.For the past month we have seen regular avalanche activity on multiple deep weak layers. A layer of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and sun crust on solar aspects was buried mid-January and is now 60-80 cm deep. Another surface hoar layer from early-January is buried 90-110 cm deep. A widespread weak layer from mid-December is composed of facets, crusts, and surface hoar and is now buried 120-160 cm deep. Finally, a rain crust with sugary facets buried late-November is near the bottom of the snowpack and is up to 200-250 cm deep. The bottom line is the snowpack structure in this region is weak. Human triggering is most likely on the shallower weak layers, but any avalanche has the potential to step down to deeper layers and become much larger.