The avalanche danger is CONSIDERABLE above 6000 feet. Recent snowfall and winds have created dangerous avalanche conditions. Today expect more snow with increasing winds. You are likely to trigger an avalanche on wind-loaded terrain and conservative decision-making is essential. In terrain sheltered from the wind, loose snow avalanches are possible due to deep unconsolidated snow. Below 6000 feet the avalanche danger is MODERATE and below 5000 feet the danger is LOW.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Look for unstable wind slabs on all aspects today, especially above 6000 feet. For much of Sunday winds were from the E-NE and would have loaded westerly aspects. Yesterday the winds shifted back to the W-SW and continued to build wind slabs on easterly aspects. While the wind speeds have not been very strong over the past 48 hours, all of the light dry powder sitting on the snowpack's surface is easily transported by even light to moderate winds. West to southwest winds are predicted to increase today which will elevate the hazard. Careful evaluation of wind-loaded terrain is essential for safe travel. Cracking in the snow under your skis or sled is a bull's eye clue that you have found an unstable wind slab.
We have some very deep, low density powder snow out in the mountains right now, especially in the Whitefish and Swan Ranges. This has made for some great skiing and riding, but in some locations it has been more unstable than what is typical here in NW Montana. You could trigger loose dry avalanches while skiing or riding today. These avalanches will generally be isolated to steep slopes and could knock you off of your machine or your feet. Also be careful of gullies and road cuts, and other terrain traps where debris from one of these avalanches could build up enough to bury you.
We removed persistent slab from the problem list due to the time that has passed since avalanches associated with older buried weak layers were observed or reported. But it is important to keep in mind that there are locations at all elevations in the advisory area where a weak snow pack structure still exists. The most commonly observed deeper instabilities are weak snow surrounding the Jan 19th crust and depth hoar near the ground. Because these weak layers do not always present obvious signs of instability, digging into the snowpack is the best way to determine their location and reactivity. Where you find a poor snowpack structure, terrain selection is important. You are more likely to trigger a deeper weak layer in locations with shallow snow (where a weak layer is closer to the surface) like steep, rocky terrain and areas that are wind scoured.
Join the Flathead Avalanche Center, Jesco Marine and Power Sports, and Bonsai Brewing Project 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.
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.
Sunday: Mark was out on peak 6996 in southern Glacier National Park. He observed moderate to strong easterly winds throughout his tour that were actively loading westerly aspects. He also noticed recently formed windslabs on easterly slopes. All of the recent wind loading was building surprisingly deep wind slabs that were tender and reactive. Adam, Jenny, and Zach were teaching an Avalanche class at WMR and found up to 18" of new low density snow. They also observed moderate winds out of the north that transported snow throughout the day. Skiers in the Swan Range reported sensative deep snow that was sluffing on slopes above 35º.
See below for all observations this season.
Several remote weather stations are not reporting this morning and snowfall totals from the past 24 hours in the Swan Range and southern Glacier Park are unknown. The Big Mountain weather station is reporting 5 new inches of snow since yesterday morning. Above 6000 feet WSW winds are light, blowing 1-5 mph with gusts to 9 mph. Temperatures range from 10 to 12º F. Today expect another 2-8 inches of snow with the Swan Range being favored for higher accumulations. Southwest winds are predicted to increase with gusts reaching up to 37 mph. Temperatures will rise into the high-20sº F.
| 0600 temperature: | 10 to 12 deg. F. |
| Max. temperature in the last 24 hours: | 17 to 22 deg. F. |
| Average wind direction during the last 24 hours: | west-southwest |
| Average wind speed during the last 24 hours: | 2-16 mph |
| Maximum wind gust in the last 24 hours: | 17-32 mph |
| New snowfall in the last 24 hours: | 3-5 inches |
| Total snow depth: | 79-109 inches |
| Tuesday | Tuesday Night | Wednesday | |
|---|---|---|---|
| Cloud Cover: | Snow with increasing winds. | Snow showers with winds increasing. | Windy with heavy snowfall. |
| Temperatures: | 22 to 34 deg. F. | 14 to 24 deg. F. | 25 to 34 deg. F. |
| Wind Direction: | west to southwest | west to southwest | west |
| Wind Speed: | 9-13 with gusts to 31 mph | 18-20 with gusts to 45 mph | 23-27 with gusts to 53 |
| Snowfall: | 2-6 in. | 1-2 in. | 6-13 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.
