Dangerous conditions exist due to warming temperatures, recent strong winds, and additional wet, heavy snow. The avalanche danger is CONSIDERABLE, and human triggered avalanches are likely. Pay attention to changing weather conditions today. Careful snow pack evaluation, cautious route-finding, and conservative decision making are essential.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Recent strong winds drifted the deep, cohesion less snow and formed slabs with variable thickness across the advisory area. In some locations these slabs are thick and reactive while other more protected areas have thin, soft slabs. No matter the depth or density of the slab I would give them time to heal before committing to any slope with a recent wind load. In exposed areas expect to find these slabs on cross-loaded mid slope features like spur ridges, tree islands, and rock out crops. Identify wind loaded terrain by looking for smooth, rounded features on the snow surface.
In many locations the wind and abundant snow formed large cornices. With the warming temperatures today and the possibility of some sun later keep a safe distance back from these while traveling above and avoid traveling below them.
Warming temperatures and relatively heavy snow over the past 48 hours helped to consolidate the snow surface and form a slab on top of light, low density snow from early in the week. Choose conservative terrain to ski or ride in while giving this storm snow time to adjust. Pay attention to obvious signs of instability like recent avalanches, shooting cracks, and collapsing in the snow pack.
Rising temperatures over the past few days and light rain at low elevations moistened and weakened the snow surface. Temperatures should continue to climb today and the possibility exists for light rain on snow. The potential for loose, wet avalanches will move up in elevation today. Loose, wet avalanches can move fast and entrain a lot of snow. Avoid terrain traps like narrow gullies, trees, and cliffs that can amplify the effect of even a small, loose, wet avalanche.
Conditions can rapidly deteriorate during these warming trends so is important to pay attention to changing conditions. Additional heavy, wet snow, prolonged sun exposure, or rain-on snow will increase the danger. The abundant, low density snow that fell early in the week is becoming less stable as recent rising temperatures and increased winds contribute to slab formation.
Join the Flathead Avalanche Center, Jesco Marine and Power Sports, and Bonsai Brewing Project on Saturday, March 4 for an afternoon of companion rescue. Various stations will be set up around the Bonsai Brewery with raffle tickets awarded for every station completed. Stop by for one station, or all of them, any time after 2:00 pm. The final raffle will be drawn at 6:30 pm.
Thursday: A snowboarder triggered a storm slab avalanche in an area known as Chicken Bones in the southern Whitefish Range (observation). BNSF Avalanche Safety Team reported 3 natural wind slab avalanches that occurred in the John F Stevens Canyon. 2 were reported in the Shed 7 slide path, and 1 in the Infinity Path. All were estimated at 1 foot deep and propagated about 50 meters wide. Skiers on Paola Ridge in the Flathead Range experienced collapsing in the snowpack at low elevations (between 3500-5000 feet). They dug a pit and performed stability tests and found instability near the Feb. 10 rain crust. At 7000 feet they dug another pit and with hard force in an Extended Column Test found a layer that was 20 cm above the rain crust that fractured and propagated. This party also noted rain below 4000 feet on their egress. Skiers on Peak 6996 in southern Glacier National Park had consitent results in Extended Column Tests. A layer within last weeks storm snow fractured and propagated nearly 2 feet deep with moderate force (ECTP 16).
Wednesday: Skiers in the Flathead Range reported unstable storm and wind slabs. They noted cracking and remote triggering avalanches while traveling along a ridgeline. Winds were in excess of 50 mph and they found wind slabs that were 2.5 feet thick.
Tuesday: Todd and Seth snowmobiled through deep powder to Kimmerly Basin and ascended the ridgeline there. They found 3 to 4 feet of light snow on top of the February 9/10 rain crust. Although mostly low density, they were able to get propagation with easy force in a storm layer approximately 14 inches from the surface. Something to watch as we add stress to the snowpack. Winds were light to moderate, but more than enough to easily transport impressive amounts of snow.
See below for all observations this season.
Our warming trend continued yesterday as temperatures approached the freezing mark. We picked up 1-4 inches of relatively heavy snow that measured .25-.5 inches of snow water equivalent. Winds were out of the southwest at 5-15 mph with gusts from 25-38 mph. Currently, temperatures above 6000 feet range from 21-28ºF, and winds continue out of the southwest at 7-20 mph. Today should see temperatures reaching the mid 30s with southwest winds at 10-20 mph and gusts in the 30s. Showers are expected to taper mid-day and then resume tonight.
| 0600 temperature: | 21-28 deg. F. |
| Max. temperature in the last 24 hours: | 22-31 deg. F. |
| Average wind direction during the last 24 hours: | west-southwest |
| Average wind speed during the last 24 hours: | 15-25 mph |
| Maximum wind gust in the last 24 hours: | 20-38 mph |
| New snowfall in the last 24 hours: | 1-7 inches |
| Total snow depth: | 94-125 inches |
| Friday | Friday Night | Saturday | |
|---|---|---|---|
| Cloud Cover: | Warming temperatures and tapering showers. | Increasing showers. | Cold front moving into the area with snow showers. |
| Temperatures: | 31-41 deg. F. | 22-30 deg. F. | 28-38 deg. F. |
| Wind Direction: | southwest | southwest | west - southwest |
| Wind Speed: | 16-20 gusts 31-39 | 15-17 gusts 29-32 | 12-13 gusts 24-29 |
| Snowfall: | 1 in. | 2-3 in. | 1-3 in. |
| Snow Line: |
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
