The avalanche danger is CONSIDERABLE above 6000 feet. Recent snowfall and winds have created dangerous avalanche conditions. You are likely to trigger an avalanche on wind loaded terrain and conservative decision making is essential. Evaluate all terrain that has received wind loading or substantial new snow before committing to a slope. Below 6000 feet the danger is MODERATE and below 5000 feet the danger is LOW. Safe backcountry travel techniques should be practiced.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Wind speeds increased once again yesterday afternoon and overnight and continue to drift the recent moderate density snow onto typical leeward aspects. This snow is being deposited onto wind slabs formed over the past few days. Due to last weeks abundant low density snow some of these slabs are impressively thick, especially in the alpine. Wind slabs can take up to a week to stabilize and with the recent unusual weather it is best to error on the side of caution and continue to give them a wide berth. This problem should be mostly confined to upper elevation locations but in favored windy locations these slabs will present themselves on cross-loaded mid slope features like spur ridges, tree islands, and rock out crops. Identify wind loaded terrain by looking for smooth, rounded features on the snow surface.
In many locations the wind and abundant snow formed large cornices. Because these are recently formed keep a safe distance back from these while traveling above and avoid traveling below them. Saturday, skiers in the Apgar Range accidentally triggered a cornice failure. This shows the sensitivity that these wind features currently possess.
Thanks to everyone who joined us Saturday for an afternoon of companion rescue at Bonsai Brewing Project. Thanks to Jesco Marine and Power Sports and Bonsai Brewing Project for the great raffle prizes.
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.
Saturday: Riders in the Swan Range reported a rider triggered avalanche 4-5 feet deep and 300 yards wide. It appears to have occurred on a north to northeast aspect at 6500'. Fortunately the 2 riders were able to ride out of the slide and were uninjured. Skiers in the Nyack area of the Flathead Range reported large slides in both Cascadilla and Wahoo Creeks. Skiers in the southern Apgar Range of Glacier Park reported large cornices and a skier triggered cornice failure.
Friday: A snowboarder triggered a 3-4' deep avalanche in the Skook Chutes, in the southern Whitefish Range, but fortunately was uninjured (observation). FAC staff were in the Apgar Range yesterday and experienced multiple collapses (whumpfs) and shooting cracks between 4000 and 5200 feet (summit of Apgar Mt.). Guy and Mark traveled into Cascade Creek, in the Flathead Range, where they found moist snow at low elevations that resulted in numerous rollerballs on their descent. At upper elevations they noted nearly 50" of settled snow on top of the February 16 rain crust. Active wind transport was observed and a recent slab avalanche was evident in Rescue Creek.
See below for all observations this season.
Yesterday was a mixed bag of mild temperatures, a few breaks of sun and periodic intense snowfall rates. Due to settlement, weather stations are reporting just a couple inches of new snow with the Swan Range being favored with up to 0.6" of precipitation at Noisy Basin. Winds were out of the southwest at 4-28 mph with gusts from 7-38 mph. Currently, temperatures above 6000 feet range from 11-17ºF with winds out of the southwest at 1-12 mph with gusts of 8-17. Today should see temperatures a bit cooler and reaching the upper teens to mid 20s with light southwest winds and occasional moderate to strong gusts. Convective shower activity may deposit a couple additional inches of snow. Light snow showers will continue into tonight..
| 0600 temperature: | 11-17 deg. F. |
| Max. temperature in the last 24 hours: | 25-31 deg. F. |
| Average wind direction during the last 24 hours: | West-southwest |
| Average wind speed during the last 24 hours: | 4-28 mph |
| Maximum wind gust in the last 24 hours: | 7-38 mph |
| New snowfall in the last 24 hours: | 1-4 inches |
| Total snow depth: | 96-126 inches |
| Monday | Monday Night | Tuesday | |
|---|---|---|---|
| Cloud Cover: | Convective snow showers with cooler temperatures. | Cool temperatures with light snow showers. | Cooler temperatures continue with light snow. |
| Temperatures: | 21-31 deg. F. | 9-18 deg. F. | 21-30 deg. F. |
| Wind Direction: | Southwest | West-southwest | West-southwest |
| Wind Speed: | 10-11 mph with gusts to 24 | 9-12 mph with gusts to 24 | 9-17 mph with gusts to 33 |
| Snowfall: | 1-4 in. | 1-3 in. | 1-2 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.
