Flathead Range & Glacier NP

Stop and think twice if you find yourself on firm snow that doesn't allow you or your machine to sink below the snow surface. On isolated slopes at upper-elevations, these hard slabs may be thick enough and wide enough to bury you if triggered. Slopes sheltered from the wind harbor softer snow and safer riding. 

With little new snow the past few days, the primary driver for avalanche conditions is the shifting winds. Over the past 48 hours, winds have veered from westerly to easterly or northerly, then back to westerly again. It's a repeat of a cycle that occurred earlier in the week, though the timing is a little different in the eastern and western halves of the forecast region. As the recent snow settles, there's less snow available for transport, so slabs aren't growing much. 

While you can find evidence of the winds at all elevations, you'll find reactive slabs large enough to bury or injure a person only on isolated slopes. The most likely suspects are upper-elevations start zones steeper than about 35 degrees where the slabs are hard and a foot thick or more. These hard slabs may have been top-loaded into usually windward slopes by the northerly and easterly winds. They don't allow a person or machine to sink in far and often feel or sound hollow. You can trigger them from spots where the slab is thinner, like convexities or rocky areas. They may be masked by the few inches of new snow that fell overnight or falls this morning.

At mid-elevations, forecast teams and observers continue to report a snowpack that's right-side up - progressively harder with depth, and few, if any, dense layers over soft layers. Cam found the Dec. 3 Melt-Freeze crust buried over 2 meters deep Wednesday in the Flathead Range, with no sign that the facets around the crust were reactive. It wasn't present on southerly slopes where I dug in John F. Stevens Canyon. A rider in the southern Whitefish Range did not report failures on this layer Tuesday. Forecasters and riders are fiding stable, fun riding on sheltered slopes at mid elevations.

People are also reporting good coverage at low elevations in the Middle Fork. Good coverage can still be a relatively shallow snowpack, with large temperature gradients due to the Arctic air funneling through the valley. Ths low elevation snowpack is weakening, at the surface or above a mid-December rain crust. Neither poses a hazard now, but could be troublesome if loaded rapidly and with significant snowfall.