An avalanche warning is in effect.
Two feet of new snow and strong winds have created dangerous avalanche conditions in the mountains. The hazard will continue to rise as more snow arrives today.
A sensitive storm slab exists on all aspects at mid and upper elevations. Strong winds have built wind slabs on multiple aspects. Below the rain/snow line, wet snow avalanches are possible.
Travel in avalanche terrain is not recommended today.
In the Rattlesnake, there have been 2 feet of new snow since Friday. Another 10-20 inches of snow is expected today.
Snow densities are upside down, with heavier dense snow on top of lighter snow. This has created an especially sensitive storm slab on all aspects. Avoid slopes steeper than 30 degrees, convex rollovers, and terrain traps.
Strong ridgetop winds out of the west have created fresh wind slabs on east aspects. Observations from yesterday reported the strong winds were also transporting snow at mid elevations and wrapping around terrain features. Yesterday in the Rattlesnake, wind slabs up to 3 feet deep were easily triggered. Today these slabs could be even deeper.
Wind slab can be identified by its smooth rounded appearance. If you experience cracking or collapsing, these are good indicators you are on a wind slab.
(2/19/2023)
A large winter storm is currently impacting all forecast zones creating dangerous avalanche conditions. Since Friday, 3 feet of new snow have fallen in Seeley Lake, 2 feet in the Rattlesnake, and 1-2 in the Bitterroot with higher totals in the north. Winds have been strong and steady out of the west throughout the storm. Snow will continue today, with another foot or two expected by evening across all zones.
Today, expect storm slabs at all elevations. Yesterday, observations reported “upside down” snow or snow with higher densities above lighter density snow. This can create conditions where storm slabs are more sensitive and propagate further. There are also widespread sensitive wind slabs in all zones. There is a lot of snow available for transport, and a steady west wind has built large wind slabs on multiple aspects.
Temperatures could rise into the mid 30s, potentially low 40s at low elevations in the Bitterroot. There is uncertainty about where the rain/snow line will be today. Temperatures in Seeley Lake will stay cold enough to avoid a wet snow avalanche problem. Yesterday, a light freezing rain was reported up to 7000’. Rain falling on fresh storm snow creates dangerous avalanche conditions and a natural avalanche cycle. If you find yourself getting rained on today, stay out of avalanche terrain and be very careful traveling under avalanche paths.
We have been tracking a buried facet/crust combination in the Bitterroot and portions of the Rattlesnake. This layer has not produced any avalanches lately. However, it is still concerning in all areas with a stout buried crust and a cohesive slab above it. The only way to identify this layer is to dig.
Excellent skiing and riding conditions exist out of avalanche terrain today.
Let us know what you are seeing by submitting an observation.
Ski and ride safe!
