Avalanche Forecast

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Friday

Thursday is expected to be rather lackluster, but things get a lot more interesting as we head into the weekend. A rather bullish Arctic front is slowly moving south while a turbulent thrust of warm air is staging in the eastern Pacific. This clash of opposing systems should generate significant snow and wind, but the exact location and intensity is difficult if not impossible to pin down right now. The region could pick up 20 to 40 cm by Sunday evening. Stay tuned for more details. THURSDAY: Increasing cloud cover, freezing level at valley bottom, light west/southwest wind, trace of snow possible. FRIDAY: Overcast skies, freezing level at valley bottom, moderate west/southwest wind, 5 to 15 cm of snow possible. SATURDAY: Overcast skies, freezing level at valley bottom, moderate to strong northwest wind, 5 to 15 cm of snow possible.

On Tuesday natural avalanche activity was widespread, running on all aspects and elevations. Storm and wind slabs were reported to size 3.0, persistent slab avalanches failing on the mid-December interface ran to size 3.5. A size 2.5 avalanche on a northeast facing slope at 1920 m resulted in a single fatality. More details are available here.On Monday a widespread natural avalanche cycle was driven by warming temperatures and up to 100 cm of storm snow. Avalanches to size 3 were reported from a variety of aspects and elevations. Of particular interest was a size 3 avalanche that was remote triggered by a skier on a south facing slope at 1900 m, failing on the mid-December interface.On Saturday, a human-triggered size 2.5 avalanche was reported near 2300 m on a south west aspect in Glacier National Park. See the MIN report for incident details.

60 to 120 cm of snow fell between Sunday and Tuesday night.  On Monday temperatures warmed up to -1 C at tree line. Winds have been strong to extreme from the south which has built cornices and formed wind slabs on lee (down wind) slopes.The new snow sits on a complex snowpack and there are three main weak layers that professionals are monitoring:1) 80 to 110 cm of storm snow sits on a crust and/or surface hoar layer from mid-January. The crust is reportedly widespread, with the possible exception of high elevation north aspects. The mid-January surface hoar is 5 to 20 mm in size and was reported at tree line elevations and possibly higher. 2) Deeper in the snowpack, the early-January persistent weak layer is 110 to 140 cm below the surface. It is composed of surface hoar on sheltered slopes as well as sun crust on steep solar aspects and is found at all elevation bands. Snowpack tests show sudden fracture characters and signs of instability such as whumpfs, cracking and recent avalanches. 3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 120 to 170 cm deep. It is most problematic at and below tree line.