The avalanche danger is MODERATE above 5000 feet. More snow and moderate to strong winds today will continue to form wind slabs making it possible to trigger an avalanche on wind loaded slopes. Be cautious of all wind-loaded terrain today. Carefully evaluate the conditions before committing to a slope. Below 5000 feet the danger is LOW. Identify and avoid features of concern.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Increasing West to Southwest winds will continue to drift snow onto leeward aspects. In some locations this snow is accumulating on older wind slabs formed over the weekend and more snow and wind is in the forecast. Wind slabs can take up to a week to stabilize, so err on the side of caution and carefully assess all wind-loaded slopes before committing to them. This problem should be mostly confined to terrain above 6000 feet, but be on the lookout for wind slabs at all elevations today. Favored windy locations such as spur ridges, tree islands, and rocky outcrops are all examples of terrain features that could harbor wind slabs. Identify wind loaded terrain by looking for smooth, rounded features on the snow surface. Shooting cracks are a tell-tale sign that the snow is unstable.
In many locations the wind and abundant snow formed large cornices. Keep a safe distance back from cornices while traveling above them and avoid traveling below them. Monday, skiers in the Whitefish Range triggered a cornice failure which is a great indication that some of these wind features are unstable.
Tuesday: Seth was on Blaine Mountain in the Northern Swan Range (observation). He found a lot of previous wind transport near the ridges with impressive cornice build up and some signs of near surface instability. Stability tests in the snowpit identified some weakness in the top 6 inches of the snowpack, otherwise not much to note. A group of skiers in the Baldhead Mountain area of the Flathead Range reported mostly unconsolidated surface snow with no propagation across the column in their stability tests.
Monday: Erich, Guy, and Zachtern toured up Skookaleel ridge in the southern Whitefish Range (observation). They noted the lack of wind slabs in the area, but were also travelling in more sheltered terrain. In three different snowpits dug on S, NE, and N aspects their extended column tests resulted in partial breaks under moderate force within the top 40-50 cm (16-20 inches) of the snowpack. But fractures did not propagate across the entire column. They did not see any recent avalanches save for one cornice fall that was intentionally triggered by another party. The group triggering the cornice noted that it broke out much larger than they expected. This same party of skiers also dug on a SE aspect at 6500 feet. They observed multiple fractures in the upper 60 cm of the snowpack, but no propagation in their extended column test. Skiers in the Apgar Range found about 115 cm of snow on top of the Feb. 10 crust and did not observe any signs of instability while touring or in their snowpit. They reported light to moderate winds and noted some cornice development above 6000 feet.
Sunday: Mark walked the ridge east of WMR where he noted storm snow instabilities within the recent moderate density snow that fell over the weekend. In exposed areas a thin wind slab was forming on the surface. Skiers in the Marion Lake area of the Flathead Range reported a sun crust 15-25 cm below the surface on southerly aspects. In their stability tests they had failure on the sun crust and propagation with hard force at 80 cm below the surface. Skiers in Wahoo Creek in the Flathead Range reported a 5 cm ice crust 60 cm from the surface which produced failures in their pit, but no propagation was observed. Skiers at the Challenge cabin in the Flathead Range reported a mixed bag of weather conditions Friday - Sunday. They also reported a sun crust that had formed on solar aspects which was subsequently buried by 25 cm of dense snow and was reactive with easy force. An upper elevation avalanche triggered by a cornice failure was observed.
See below for all observations this season.
Yesteday was cool with a few breaks in the clouds alternating with periods of semi-intense snowfall. Over the past 24 hours another 0-5 inches of snow accumulated. Winds have been out of the southwest at 2-24 mph with gusts reaching up to 57 mph this morning at Snowslip. Currently temperatures above 6000 feet range from 19 to 26 ºF with winds out of the west to southwest at 7-19 mph with gusts to 20-57 mph. Today we should see scattered snow showers with another 1-4 inches possible. Expect high temperatures to reach the upper teens to mid-20s ºF with continued moderate to strong west to southwest winds with occasional stronger gusts.
| 0600 temperature: | 19 to 26 deg. F. |
| Max. temperature in the last 24 hours: | 20 to 32 deg. F. |
| Average wind direction during the last 24 hours: | southwest |
| Average wind speed during the last 24 hours: | 2-24 mph |
| Maximum wind gust in the last 24 hours: | 3-57 mph |
| New snowfall in the last 24 hours: | 0-5 inches |
| Total snow depth: | 98-130 inches |
| Wednesday | Wednesday Night | Thursday | |
|---|---|---|---|
| Cloud Cover: | Mostly cloudy with scattered snow showers and increasing wind. | Snow showers increasing to the South. | Snow and winds shifting to the East. |
| Temperatures: | 22 to 34 deg. F. | 5 to 20 deg. F. | 16 to 32 deg. F. |
| Wind Direction: | Southwest | South to Southwest | Northeast to East |
| Wind Speed: | 14-15 with gusts to 39 mph | 9 with gusts to 25 mph | 5-7 mph |
| Snowfall: | 0-4 in. | 1-6 in. | 3-7 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.
