We were missed by the latest storm. The avalanche danger is MODERATE above 6000 feet. Shifting 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.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Wind slabs should be expected at all aspects at uppper elevations as winds have shifted to the NNE and are now depositing snow on S and SW aspects. Look for signs of recent wind-loading such as smooth rounded pillows on all aspects today, 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.
The southern part of the advisory area may have gotten some snow, but we were mostly missed by the latest storm. We still have concerning weak layers in the snowpack. These layers can be found at the bottom, middle and top of the snowpack. To this point, these layers have not shown instability or sensitivity, but it is possible to find places where they may be triggered. It is important to dig into the snow and look for these layers. With the increased load and strengthening of slabs above these layers, the consequences should they be triggered are increasing. Where weak 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. Evaluate the snowpack carefully today and look for tell-tale signs of instability such as shooting cracks that run out from under your skis or sled.
Tuesday: Todd and Seth traveled up Lost Johnny to Hash Mountain in the Northern Swan Range. Winds had shifted to the East, and although light, were increasing as the day went on. Previous wind loading was prevalent on East and North aspects, although slabs did not appear to be sensitive. Some strengthening is occuring in the snowpack, however, we still found concerning weak layers of buried surface hoar and facets around crusts. These layers were not sensitive and did not appear to be prone to propagation, but they easily could be in other locations. Adam was in the Big Slide area of the Southern Whitefish Range and also found wome weak layers in the snowpack, but did not have any propagation. He did note some new surface hoar development.
Also on Tuesday, we received public observations from Running Rabbit Mountain and Cameahwait Mountain in the Flathead Range. Both reported signs of previous wind loading but no obvious signs of instability and no propagation in stability tests.
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 -4 to 5 °F, winds are averaging 3-16 mph, gusting to 7-26 mph out of the north-northeast. Temperatures are expected to stay in the single digits to low teens today with continued light to moderate winds, especially near the Continental Divide. There was no new snowfall overnight. Tonight into tomorrow also should be dry with cooler temperatures and N-NE winds.
| 0600 temperature: | -4 to 5 deg. F. |
| Max. temperature in the last 24 hours: | 10 to 28 deg. F. |
| Average wind direction during the last 24 hours: | North northeast |
| Average wind speed during the last 24 hours: | 3-16 mph |
| Maximum wind gust in the last 24 hours: | 7-26 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 53-68 inches |
| Wednesday | Wednesday Night | Thursday | |
|---|---|---|---|
| Cloud Cover: | Cooler and Partly Sunny | Clear to Partly Cloudy | Mostly Sunny |
| Temperatures: | 10 to 19 deg. F. | -6 to 4 deg. F. | 11 to 18 deg. F. |
| Wind Direction: | E-NE | E-NE | E-NE |
| Wind Speed: | 10-13 mph | 9-11 with gusts to 24 mph | 5-10 with gusts to 23 mph |
| Snowfall: | 0 in. | 0 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.
