The avalanche danger is MODERATE above 5000 feet and LOW below this. Wind slabs formed over the past weekend need time to stabilize. You are more likely to trigger a wind slab avalanche in alpine terrain, but be cautious of all wind-loaded slopes. It is also possible to trigger an avalanche on an older persistent weak layer. Today's potential above-freezing temperatures and abundant sunshine may increase the avalanche danger. Pay attention to these changing conditions and adjust travel plans accordingly.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
While the winds have calmed down a bit over the last 24 hours, wind slabs can take several days to gain strength and stabilize on the slope. In alpine terrain there is still soft snow available for wind transport. Moderate to strong southwesterly winds over the weekend have drifted snow onto leeward aspects typical for this region. Wind speeds have decreased and little to no wind-loading was observed yesterday. But still treat all wind-loaded slopes with caution. Wind slabs can be identified by looking for smooth, rounded pillows of snow. Shooting cracks in the snow surface are a tell-tale sign that you may have found an unstable wind slab.
Unusual weather patterns this winter have produced a snowpack that contains a variety of weak layers. The impressive snowfall last week has exacerbated this problem by capping these layers with a thick slab. Stability tests are still showing reactive results around the January 19 crust and, in isolated locations, the depth hoar at the bottom of the pack is still a concern. These weak layers do not always present obvious signs of instability and digging into the snowpack is the best way to determine their location and reactivity. Also pay attention to the snowpack in the mid-elevations. Thanks to last week's storm we now have a thick slab deposited on top of the above-mentioned weak layers. Steep slopes well below tree-line should be approached with caution.
Above freezing temperatures and abundant sunshine could also affect the slab sitting atop the persistent weak layers. Evaluate snow and terrain carefully and avoid sunny slopes later in the day in order to manage the uncertainty associated with warming and effects on our persistent slab problem.
Pay attention to changing conditions today. Slopes on sunny aspects may become more unstable later in the day due to the abundant sunshine and warming temperatures. Cold overnight temperatures and the widespread rain crust will help keep the snow in place, but wet loose avalanches and cornice failures could become a concern in some locations. Look for signs that the snowpack is starting to become unstable due to the warm sunny weather. These include rollerballs, tree bombs, and recent wet loose sluffs on steep slopes, especially near rocks and trees.
Ladies, are you interested in refreshing your avalanche knowledge or looking for a great introduction to avalanche safety? If so, join us at The White Room Mountain Shop, in Whitefish, on Thursday, February 16th at 6:30 pm for a free, engaging, and entertaining 1 hour avalanche awareness presentation. The class includes general information about avalanche hazard, how to avoid it, and proper equipment for traveling in avalanche terrain.
First we would like to thank all those who have been submitting observations recently. These observations are invaluable and improve our forecasts. Several observers have submitted reports from across the advisory area documenting the widespread avalanche activity from last week (see our Observations Page). Thank you!
Monday: Zachtern and I were in Wahoo Creek in the Flathead Range where we observed widespread avalanche activity from last week but no recent avalanches. We reached about 6000 feet in elevation which did not put us above the rain crust. We investigated the large avalanche that ran last Tuesday (2/7) in an unnamed drainage off the north end of the ridge dividing Wahoo and Cascadilla Creek drainages (Avalanche Observation). Guy and Erich were in Lost Johnny in the Swan Range. The also documented the avalanche carnage from last week (Avalanche Observations) but did not see any new avalanche activity. They also noted the rain crust reached up to 6600 feet. They reported light to calm winds with little to no wind-loading in the alpine. In a snowpit at 6500 feet they had propagation with hard force on the Jan 19th crust. Skiers in the Swan range noted the numerous avalanches from last week. One party did have propagation on the Jan 19th crust in an Extended Column test at 6000 feet on a north aspect. Skiers in the Whitefish Range noted the crusts were softening on sunny aspects by 1 pm and also reported surface hoar on northerly aspects. NPS rangers reported numerous avalanches that during last week's cycle in southern Glacier Park.
See below for all observations this season.
In the past 24 hours temperatures ranged from the mid-teens to 40ºF with winds out of the southwest that averaged 2-11 mph with maximum gusts of 5-22 mph. Currently, temperatures are inverted with colder air settled in the valleys. Above 6000 feet temperatures range from 25-33ºF and winds are mostly from the southwest ranging from 1-19 mph with gusts from 6-20 mph. Today the high pressure ridge remains parked over the region. We should see mostly sunny skies, light winds, no precipitation, and temperatures reaching the upper 30s to low 40s.
| 0600 temperature: | 25 to 33 deg. F. |
| Max. temperature in the last 24 hours: | 29 to 40 deg. F. |
| Average wind direction during the last 24 hours: | Southwest |
| Average wind speed during the last 24 hours: | 2-11 mph |
| Maximum wind gust in the last 24 hours: | 5-22 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 71-103 inches |
| Tuesday | Tuesday Night | Wednesday | |
|---|---|---|---|
| Cloud Cover: | Sunny and warm | Clear and cool. | High pressure breaks down late in day |
| Temperatures: | 33 to 43 deg. F. | 12 to 25 deg. F. | 33 to 45 deg. F. |
| Wind Direction: | southwest | southwest | south to southwest |
| Wind Speed: | 6-7 mph | 7-8 with gusts to 23 mph | 7-10 with gusts to 28 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.
