Expect changing conditions with avalanche danger rising to CONSIDERABLE by this evening as a potent storm begins to impact the forecast area. Storm instabilities will develop through the day and will begin to add stress to a more consequential persistent slab problem. Monitor new snow accumulations and intensity while allowing a wide buffer in terrain selection to manage for lurking deeper instabilities.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Cohesive slabs from 2 to 4 feet thick overlying weak, faceted snow exist throughout our forecast area. The problem has become stubborn or unreactive, evidenced by a lack of recent avalanches or signs of instability. However, new snow today will begin to add weight to poor snowpack structures that persist, most commonly at mid and upper elevations. Watch for collapsing and shooting cracks, obvious signs of an unstable snowpack, but the absence of these red flags is not a get out of jail free card. High consequences remain with this complex problem so carefully assess the snowpack and use cautious route-finding, avoiding unsupported slopes and steep rollovers above terrain traps.
Rapid snowfall will increase the size and sensitivity of storm slabs throughout the day, especially in wind affected terrain. Slabs fracturing under the weight of a skier or rider will become easy to trigger as dense storm snow accumulates over lower density or weaker snow. These should be relatively small in size but could become large enough to bury you by this evening. Use caution near terrain traps such as trees and gullies, and evaluate new snow bonding on small test slopes before committing to bigger terrain.
The Flathead and Swan Ranges picked up 2" to 5” overnight. Significant changes are on the horizon with a potent storm system pushing copious amounts of moisture into our forecast area starting today. This storm will be focused to our south, so expect changes to occur more radidly in the favored southern ranges. The danger will rise to Considerable by this afternoon or tonight, depending on the intensity and amount of new snow that falls. Rapid snowfall will be adding more stress to a poor snowpack structure with weak, faceted snow buried under 2 to 4 foot persistent slabs. During a loading event like this and uncertainty surrounding larger, deeper avalanche problems, its best to notch back your terrain choices.
A potent winter storm begins impacting northwest Montana in earnest today and is expected to last through Saturday. At 4 am, storm is positioned off the Washington coast and our region is under a light southwest flow. Copious amounts of Pacific moisture are expected to slam into cold, arctic air moving south out of Canada over the next 48 hours. Expect an increase in wind speeds and gusts during the day Friday with intense snowfall overnight Friday. Highest snowfall amounts are anticipated just south of our forecast area but impressive snowfall amounts are not out of the question for our northern zones. We can anticipate 2-3 feet of snow south and 1-2 feet of snow north by end of the day on Saturday.
| Thursday | Thursday Night | Friday | |
|---|---|---|---|
| Cloud Cover: | Snow | Snow | Heavy snow |
| Temperatures: | 20 to 25 deg. F. | 10 to 15 deg. F. | 5 to 10 deg. F. |
| Wind Direction: | SW | NE | NE |
| Wind Speed: | 5 to 15 mph with gusts of 25 mph | 15 to 20 with gusts of 25 mph | 15 to 25 mph with gusts of 30 mph |
| Snowfall: | 3-5 in. | 3-5 in. | 4-8 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.
