Warming temperatures, strong winds, and relatively heavy snow created dangerous conditions. The avalanche danger is CONSIDERABLE above 5000 feet, and human triggered avalanches are likely. Continued warming and additional snowfall today will cause sensitive storm slabs to become more widespread as the day progresses. Below 5000 feet where human triggered avalanches remain possible the danger is MODERATE.
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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, cohesionless snow and formed thick, reactive wind slabs across the advisory area. Given the winds ability to transport the light snow long distances these slabs will not be simply confined to leeward ridgelines. 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. Cornices along the ridgeline are also a great indicator that the wind has been working on the slope below.
The deep, low density snow that accumulated across the area throughout the week was all fun and games with out a cohesive slab involved. But now warming temperatures and wind helped to form a slab on the surface that is tough for the weak snow below to support. Pay attention to obvious signs of instability like recent avalanches, shooting cracks, and collapsing in the snow pack. Dig a quick pit to look for dense snow sitting on top of dry, lower density snow.
Pay attention to changing conditions today. The abundant, low density snow that fell early in the week is becoming less stable as rising temperatures and increased winds contributed to slab formation. It is important to evaluate storm slabs on all aspects that formed on top of dry, cohesionless snow. Keep in mind that the danger may continue to rise into the afternoon and evening as warming temperatures and additional snow cause the problem to become more widespread.
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.
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.
Monday: Guy and Zach were in Spider Bowl in the Swan Range. They found some deep powder and observed multiple small loose dry avalanches on steep slopes. They also noted very little wind-loading. Two different parties of skiers in the Flathead Range also noted minimal wind-slab development, but mentioned that they stuck to more sheltered terrain below 7000 feet. Both groups experienced some sluffing in the loose surface snow. BNSF Avalanche Safety toured in John F. Stevens Canyon in southern Glacier Park. Light to moderate SW winds were actively loading easterly aspects on terrain above 6000 feet. They noted some minor shooting cracks in the newest wind slabs.
See below for all observations this season.
Our SNOTEL site issues continue this morning as they stopped reporting late last night. Before going down they reported 2-8 inches of new snow and 0.3-0.5 inches of snow water equivalent. Winds in the past 24 hours were out of the west-southwest at 10-20 mph with gusts from 25-55 mph. Current temperatures at Mountain Weather Stations range from 19-21º F. Winds continue out of the southwest at 10-17 mph gusting from 15-25 mph. Today, expect light snow showers with southwest winds at 15-25 mph, and temperatures rising to the low 30s.
| 0600 temperature: | 19-26 deg. F. |
| Max. temperature in the last 24 hours: | 21-27 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: | 25-55 mph |
| New snowfall in the last 24 hours: | 3-8 inches |
| Total snow depth: | 92-120 inches |
| Thursday | Thursday Night | Friday | |
|---|---|---|---|
| Cloud Cover: | Warming temperatures and light snow showers. | Continued snow showers. | Continued warming with strong winds and isolated showers. |
| Temperatures: | 28-38 deg. F. | 22-28 deg. F. | 35-42 deg. F. |
| Wind Direction: | southwest | southwest | southwest |
| Wind Speed: | 14-17 gusts 29-32 | 18-23 gusts 33-41 | 17-22 gusts 36-41 |
| Snowfall: | 1-2 in. | 2-5 in. | 1 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.
