Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Yesterday (Sunday), two riders were caught and carried roughly 150 feet before coming to a stop uninjured. This slide appeared to have involved wind-drifted snow resting on a crust. This is a clear sign for us going out today to steer around and avoid slabs of wind-drifted snow. Provide a wider margin for error where slabs rest over a faceted crust. Seek out slopes sheltered from the wind for a safer and higher quality experience.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Remote weather stations are showing 1 to 2 inches of new snow overnight. Marias Pass and Snowslip weather station is reporting speeds of 13 to 15 mph out of the south and southwest. New and recent snow will get drifted into thin slabs reactive to the weight of a rider. These thin and freshly formed slabs will rest over a thicker, more stubborn wind slab as a result of recent strong winds. 

    Look for blowing snow as a visual clue for places to avoid. Shooting cracks around your machine or feet are signs that slabs are sensitive to the weight of a human. Seek out slopes sheltered from the wind or keep slope angles less than 35 degrees.

    (2/3/2023)

    Signs of active wind transport. Slopes where you see this occurring are slopes to avoid. 

    Photo: Brad Taylor

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–3

    A crust/facet combination exists 1 to 2 feet below the surface. This weak layer may be the culprit for a recent human triggered slide in the Flathead Range yesterday. Avalanche professionals received propagating results in snowpit tests on Thursday.

    Give slopes where you find weak snow resting on a crust a margin for error, especially in zones where winds drifted snow into a thicker slab. Dig down in the new and recent snow to locate this structure. Feel for weak, sugary snow resting on a hard crust. If you find this structure under a stiffer slab of snow, reduce slope angles to less than 35 degrees.

    (1/29/2023)

    Surface hoar is now buried 2 to 3 feet (70 to 90 cm) below the surface in terrain sheltered from the wind. This layer is highlighted by the black card in the snow. 

    Photo: Cam

Avalanche Discussion

Recent Avalanche Activity:

Yesterday, a group of riders triggered a slab avalanche in the Flathead Range (observation). This failed at approximately 5000 feet. This slide caught and carried 2 of the riders, dragging them 150 feet and over a small cliff. No riders were injured. We thank the party involved for sharing this event. This is bullseye information for us to help keep us out of harm's way today. 

Weather:

Last night's storm was forecasted to favor the southern end of our forecast zone, but it didn’t quite materialize. Noisy Basin in the Swan Range picked up .3 inches of snow water equivalent (SWE), which resulted in 1 to 3 inches of snow. Other remote weather stations throughout the forecast area are showing 1 to 2 inches of new snow overnight.

Wind speeds out of the southwest are back at it and blowing at speeds capable of transporting snow in all three forecast zones. Wind speeds for the past four days were unusually windy. South and southwest winds reached sustained speeds in the moderate to extreme categories.

Snowpack:

The theme of recent observations is wind-affected surfaces. Observations paint a picture of wind-scoured surfaces on windward slopes, and slabs of drifted snow on wind-loaded slopes. Reports of natural and human-triggered avalanches involving wind-drifted snow continue to trickle in. These ranged in size from small (harmless to a human) to large (large enough to bury and injure a human).

Weak layers exist in the upper snowpack throughout our forecast area. Weak snow is now getting buried deep in the Swan Range, making it more difficult to trigger. Propagation in snowpit tests and active loading makes us hesitant to drop the likelihood for now. A facet/crust combination in the Flathead Range is showing untrustworthy signs in snowpit tests. So far, we have no confirmed avalanches on this weak layer. We suspect it may be the culprit in a recent human-triggered avalanche. Persistent weak layers of surface hoar and facets exist in the Whitefish Range, but are not showing signs of it being a problem yet. So far, we contribute this to the lack of snow resting on weak layers. A loading event may bring this back to listing it as a problem. 

Terrain:

The primary avalanche problem to manage right now is wind slabs. You can manage this problem by searching for snow sheltered from the wind. This may require more searching due to strong winds. Further down the slope and in treed terrain may be a good place to start looking. The higher you climb and the closer you get to ridgelines, the more likely it is you’ll find a wind slab.

Persistent weak layers are more of a concern on the same aspects where winds are drifting snow into thicker slabs. This does simplify our terrain selection. Treat slopes on north through east aspects as suspects for wind slabs and persistent slabs. Reduce your chance of getting caught in a slide by reducing your slope angle to less than 35 degrees on those aspects. 

Come one, come all! Flathead Avalanche Friends Fest, a four-day festival from Feb 8-11, has a full schedule with mini-clinics, a keynote speaker, après, and a Big-A$$ Raffle. A little something for everyone. We hope you can join us to celebrate our community, learn about snow, and support our safety mission. Learn more here.

Motorized Level 1 - Instructed by Eric Knoff and Six Points Avalanche Education from Tuesday, February 7, 2023, to Thursday, February 9, 2023. More details are here

 

 

 

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