The avalanche danger is MODERATE above 6000 feet. Winds continue to drift snow onto leeward aspects forming fresh wind slabs and putting additional weight onto existing slabs. In some locations these slabs are being deposited on top of a rain crust. Buried weak layers still exist and remain a concern. Choose conservative terrain in areas where you find a weak snowpack structure. The Flathead and Swan ranges could see more accumulating snow today – see Flathead/Swan advisory HERE.
?
Above 6500 ft.
?
5000-6500 ft.
?
3500-5000 ft.
Moderate to strong winds have been drifting snow onto lee aspects forming wind slabs. Winds have predominantly been blowing from the W and SW over the past 24 hours. Look for signs of recent wind-loading such as smooth rounded pillows, especially above 6000 feet. All wind loaded terrain should be viewed with suspicion. In some locations these slabs have been deposited onto a crust which will make for a great sliding surface. Also, in certain areas these new slabs are accumulating on a variety of weak layers such as buried surface hoar and faceted snow. These weak layers may start failing under the growing weight of a thickening wind slab.
Weak layers formed throughout this season can still be found in our snowpack and remain a concern. These layers can be found at the bottom, middle and top of our pack. The near surface weak layers exist immediately below the January 19 crust and can be identified easily. The other weak layers take a bit more effort to identify and require that you dig into the snow to search them out. Where these layers are found conservative decision making is the solution. Avoid areas that are steep and rocky and/or have a shallow snowpack. These areas are where the deeper weak layers have been preserved.
The forecast is calling for more snow today in the Flathead and Swan Ranges – see the separate advisory HERE.
Monday: Erich and Guy traveled into the Tunnel Ridge area in the Flathead Range. They experienced strong southwest wind transporting snow to leeward aspects and even cross-loading ridges (video). They avoided wind loaded slopes, and noted the Jan. 19 crust with weak snow below it at elevations below about 6000 feet. They observed localized cracking along ridges, but observed no natural avalanche activity. BNSF Avalanche Safety toured in John F. Stevens Canyon. They noted active wind-loading onto easterly aspects above 6000 feet but did not observe any recent avalanche activity.
Sunday: Mark was in the southern Whitefish Range where warm temperatures and abundant sunshine moistened the surface snow on solar aspects. At lower elevations he was able to initiate small wet loose slides on the descent. Near surface instability was noted in a facet layer below the January 19 crust and in a buried layer of facets one foot below the snow surface.
Saturday: Riders in the northern Swan Range felt a whumpf or collapse in the snowpack. They also noted surface snow sliding on the underlying hard layer along with minor cracking. Skiers in the southern Whitefish Range noted active wind transport of the surface low density snow. Skiers in Rescue Creek in the Flathead Range found fresh wind slabs with wind loaded ridges and breakable crust below 6200'. Skiers in the Missions, out of our forecast area, noted windy conditions in the upper elevations with southerly slopes heating up producing rollerballs and small point releases. Skiers in the Marion Lake area of the Flathead Range found a deep snowpack on a northwesterly aspect and noted a good size wet avalanche that had terminated on the hiking trail.
See below for all observations this season.
Above 6000 feet temperatures range from 10 to 18 °F, winds are averaging 6-12 mph, gusting to 9-17 mph out of the west-northwest in the Whitefish Range and from the north-northeast in the Flathead Range. Temperatures are expected to rise into the low-twenties later today with continued moderate winds, especially near the Continental Divide. There was no new snowfall overnight, but four to seven inches of new snow is forecasted for the Flathead and Swan Ranges. Only a trace to one inch of new snow is expected for the Whitefish Range. Tonight into tomorrow, the snow tapers off and temperatures drop into the single digits or slightly below 0 °F with N-NE winds.
| 0600 temperature: | 10 to 18 deg. F. |
| Max. temperature in the last 24 hours: | 24 to 31 deg. F. |
| Average wind direction during the last 24 hours: | west - southwest |
| Average wind speed during the last 24 hours: | 6-31 mph |
| Maximum wind gust in the last 24 hours: | 7-44 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 53-68 inches |
| Tuesday | Tuesday Night | Wednesday | |
|---|---|---|---|
| Cloud Cover: | Cloudy with light to moderate snow | Partly cloudy and colder | Partly Cloudy |
| Temperatures: | 15 to 27 deg. F. | -10 to 4 deg. F. | 10 to 20 deg. F. |
| Wind Direction: | E-NE | NE | NE |
| Wind Speed: | 8-9 with gust to 20 mph | 12-14 with gusts to 24 mph | 11-14 mph |
| Snowfall: | 0-6 in. | 0-1 in. | 0 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.
