East Cabinet Mountains

An Avalanche Watch is in effect from Saturday 6 AM PST to Sunday 6 AM PST. A warm, wet storm will deliver a combination of dense storm snow and moderate to heavy rainfall to the snowpack. The snow line will likely rise to between 6,000 and 7,000 feet by Sunday evening. The combination of strong winds and rain saturating the upper snowpack may be sufficient to overload weak snow layers and cause a widespread cycle of avalanches large enough to bury, injure, or kill a person. Some of these avalanches could release naturally, and it will become very easy for backcountry travelers to trigger them. Travel in or below avalanche terrain is not recommended during this period.

With the arrival of warmer temperatures and fluctuating precipitation over the next several days, surface conditions and flavor of avalanche problems will likely oscillate between a dry and wet origin, or lumped together in a swirled-flavored avalanche cake. As the storm takes shape, it may become difficult to climb above the rain line as current forecasts suggest liquid precipitation may reach 6,000 feet before cooler temperatures arrive and push us back into the snow phase.

New snow densities are expected to be around 20 percent or possibly higher, which is a significant shift from the 5 to 7 percent storm snow that has fallen recently. This inverted layering will help form reactive storm slabs with lesser snow depths than typical. As you move closer to the treeline and above, you may find deeper wind-drifted areas that could produce a larger slide, and where terrain management may need adjustment. Lens-shaped pillows, fresh cornice growth, and the snow surface becoming harder or hollow sounding will clue you into the more worrisome places.

Weak layers - surface hoar, faceted grains, and a faceted crust - two to three feet deep are the culprit of lingering instability in the upper snowpack. Snowpack tests on slopes near treeline down to about 5,000 feet continue to produce ongoing failures in these weak grains. Well-preserved and upright surface hoar is found on north to east-facing slopes, while southeast through south to west-facing slopes harbor a breakable crust with facets looming above and below. While deeper weak grains are showing evidence of strengthening, the ability to affect weaker snow and trigger a slide appears directly influenced by overlying slab depth.

While the forecast staff and public observers have recently found overall improving conditions, we’re not ready to write off looming concerns just yet. Triggering a dangerous avalanche is still in the cards if you travel on steep, rocky, shallower areas, or where drifting builds uneven slab depths influenced by terrain twists, turns, or bends. Add 1 to 3 inches of liquid precipitation or very dense snowfall could be the straw that breaks the facets back and pushes slopes to fail naturally. If the snowpack undergoes a prolonged period of steady rain, the wetting front may advance deeper in the snowpack to the January Drought Layer (JDL). If water reaches this interface, we may be entering the wet slab avalanche realm of higher uncertainty around the exact moment a slope may fail.

Wild weather often breeds unusual avalanche behavior. You may encounter the full spectrum of wet snow hazards at lower elevations that transition to wet/dry and eventually dry conditions at the highest elevations. If decision-making around stability is too challenging or you observe non-conclusive snowpack evaluations, keep things simple and limit the temptation to thread the needle. If you experience periods of heavy rainfall or back and forth precipitation types, it may be best to call it a day and head to the barn.