An avalanche warning is in effect. Very dangerous conditions exist due to recent snow and moderate to strong winds combined with increasingly heavy, wet snow and rain at upper elevations today. The avalanche danger is HIGH above 6000 feet. Travel in avalanche terrain an run-out zones is not recommended. Below 6000 feet the avalanche danger is CONSIDERABLE. With additional precipitation today we could see over an inch of rain and heavy, wet snow above 6000 feet.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Moderate to strong southwest winds continue to drift the new snow and create slabs on the leeward sides of ridgelines and cross-load mid-slope terrain features. These slabs formed on a firm rain crust above 7000 feet in some locations that will provide an excellent sliding surface. In isolated areas these fresh wind slabs may sit on top of surface hoar formed earlier in the week.
Warming temperatures and rain on snow expected today will increase the wet avalanche hazard as the day progresses. If the snow surface is not moist already, watch for warming temperatures and snow transitioning to rain to change that throughout the day. The snow surface becoming moist/wet and pin wheels forming on steep slopes indicate that the surface snow is becoming unstable and you need to reassess the terrain you are traveling in. Loose, wet avalanches can start small but entrain a substantial amount of snow and do a lot of damage.
In addition to the loose, wet hazard the potential exists to see thin, wet slabs forming on top of the recent rain crust. Though they will be thin, they will be more difficult to manage than a wet sluff since they could potentially fracture above you. Keep in mind that even small avalanches can add rapid stress to deeper instabilities and step down.
Buried surface hoar and faceted snow about 1-2.5 feet from the surface exists. In upper elevation locations this has become a hard slab in many locations, and is increasingly more difficult to trigger. However, recent natural avalanches triggered by cornice fall within the past week show this is a low probability/high consequence scenario that should be treated with respect. A couple of these avalanches propagated far and wide (photo 1, photo 2). The additional stress put on these layers with new snow, rain on snow, and wind drifted snow may cause them to become more reactive. These hard slabs are more likely to exist on previously wind loaded slopes. This weak layer is also spotty in distribution making it tricky to identify.
Weak snow surrounding the January 28 and January 17 rain crusts also exists 2-3 feet from the surface. Recent stability tests suggest that these weak layers are gaining strength, but its' still important to dig in the snow and do a stability test. Avoid areas where you are more likely to affect these layers like in shallow snow and in steep, rocky areas.
Sunday: Mark was on Sub-Shields in the Flathead Range where wind was actively transporting the new snow and forming thin wind slabs and cornices (video). A seperate party of skiers on Sub-Shields noted about 4 inches of new snow on the rain crust and observed minimal results in stability tests (observation). Skiers in the Marion Lake area also in the Flathead Range found a layer 75 cm from the surface that fractured with hard force in Extended Column Tests and produced clean shears (Q1) in shovel shear tests.
Saturday: We were on Hash Mountain in the Swan Range and found the previous night's snow levels were higher than expected. At 7050 feet there was a rain crust with only 1-2 inches of snow on top. 10-15 mph winds were drifting the snow, there just was not much of it. We found the thin late January crust with weak snow around it 2.5 feet from the surface (photo). This layer did not fracture in our stability tests.
Friday: We were in McGinnis Creek in the southern Whitefish Range and found a wet snow surface up to at least 6000 feet. We noted a layer of decomposing buried surface hoar that was 6-10 inches from the surface that fractured in stability tests (observation).
Thursday: BNSF avalanche safety noted a moist snowpack, warm temperatures, and experienced collapsing on a southeast aspect with a shallow snowpack (observation). They also observed a cornice triggered slab avalanche on Mt. Cameahwait in the Flathead Range (photo), but are uncertain of the date of occurrence. Glacier Park rangers observed recent wet avalanche activity on the south aspects of Mt. Stanton yesterday (observation). Snowmobilers in Canyon Creek in the southern Whitefish Range also observed recent loose, wet avalanches (photo).
Wednesday: Erich found wet snow on sunny aspects with numerous small, wet loose sluffs (observation). We, along with other professionals and skiing parties in the southern Whitefish Range, observed widespread surface hoar formation (video, observations). Snowbikers in the Stryker Ridge area in the Whitefish Range also reported rollerballs, wet surface snow, and large surface hoar formation. A Two Bear Air Rescue pilot also observed cornice triggered recent wet, loose avalanche activity in the Swan Range on sunny aspects during a recent flight.
Visit our Observations page and our You Tube channel for more observations from the entire season.
Thanks to everyone for submitting observations. They are extremely useful and could help save lives.
HOW TO SUBMIT OBSERVATIONS:
Email: [email protected]
Call and leave a message: 406.387.3821
You can also submit quick observations via text: 406.241.4571 (FAC mobile)
OR
Submit Snowpack Observations: http://www.flatheadavalanche.org/node/add/snowobs
Submit Avalanche Observations: http://www.flatheadavalanche.org/node/add/avyobs
In the past 24 hours we picked up 0.5 -0.7 inches of snow water equivalent. Winds were out of the southwest at 10-20 mph with gusts from 26-47 mph. As of 4:00 am, temperatures above 6000 feet range from 27º-33º F, and winds continue to blow out of the southwest at 10-17 mph with gusts from 17-31 mph. Today we should see continued rain/snow showers with snow levels approaching 7000 feet. Winds will continue out of the west and southwest at 10-20 mph with gusts in the 40s.
| 0600 temperature: | 27-33 deg. F. |
| Max. temperature in the last 24 hours: | 28-33 deg. F. |
| Average wind direction during the last 24 hours: | SW |
| Average wind speed during the last 24 hours: | 10-20 mph |
| Maximum wind gust in the last 24 hours: | 26-47 mph |
| New snowfall in the last 24 hours: | 0-4 inches |
| Total snow depth: | 67-90 inches |
| Monday | Monday Night | Tuesday | |
|---|---|---|---|
| Cloud Cover: | Continued rain/snow with rising snow levels. | Rain/snow. | Tapering rain/snow. |
| Temperatures: | 36-43 deg. F. | 27-35 deg. F. | 37-45 deg. F. |
| Wind Direction: | W | SW | SW |
| Wind Speed: | 18-21 gusts 37-44 | 10-12 gusts 28-35 | 16-22 gusts 31-44 |
| Snowfall: | 0-4 in. | 0-4 in. | 0-3 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.
