Flathead Range & Glacier NP

Up to a foot of snow fell overnight, with more on tap for today. The avalanche danger may be higher and more widespread than it has been in quite a while. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. Cracking beneath your skis or machine indicates an instability directing you to lower-angle terrain.

The danger will be lower in areas that only received a few inches of snow, like John F. Stevens Canyon.

The third time, a charm! The Thursday and Friday storm systems were generally disappointing, but the disturbance that moved into our area mid-day Saturday has delivered. As of 0500 this morning, settled new snow depths at mid-elevation stations are around 9-12 inches in the Whitefish Range, the Swan Range, the Flathead Range, and central Glacier Park. Snow water equivalent (SWE) readings range from 0.7 to 1.0 inches.  Unfortunately, the Highway 2 corridor from John F. Stevens Canyon to Marias Pass only picked up a measly couple of inches. 

Winds have been relatively light over the past 24 hours, except for Aeneas Ridge, where average wind speeds have been 30 mph, well above the minimum threshold of 16 mph required for snow transport. Winds have shifted to the north or east at multiple stations as a weak arctic intrusion moved into the Flathead overnight. This cold air will interact with the relatively warmer, moist air from the Idaho Panhandle, producing light snow throughout the day. Where atypical winds occur, snow will drift onto westerly and southerly aspects. 

The new snow falls on 4 to 12 inches of soft snow, capping a crust. Any slides that occur today should entrain most, if not all, of the new snow above the crust. Observations report the near-surface crust to be relatively strong, but in more extensive terrain, slide debris may break through this crust into weak, faceted snow and produce a larger slide. 

Before the recent stormy period, an extensive dry snap formed weak, faceted snow or surface hoar on the surface in various locations. Observations over the past few days report mostly stable conditions with minimal instability (Observation, Observation, Observation). However, we remain concerned that today's slabs may be resting on this weak snow. On these slopes, slides may behave more like a Persistent Slab avalanche and could be triggered remotely from relatively flat terrain above, below, and to the sides of steep slopes. Resulting avalanches may break wider and higher than expected.