Lawinenlagebericht

Whitefish Range

Flathead Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
Open full map
Veraltet — dieser Lagebericht ist 7 months ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Yet another human-triggered avalanche on a buried weak layer reminds us that persistent slabs should be shaping our travel plans today. Meanwhile, if the sun shows up for a prolonged stretch, wet loose avalanches will become likely. You’ll find safe and excellent riding conditions in low-angle, shaded terrain.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Avalanches are the clearest sign of instability, and on Sunday, a skier remotely triggered an avalanche on a buried weak layer in the WMR sidecountry—the fourth human-triggered slide in the past five days. Tracks are widespread, and many (likely most) slopes are stable, but some clearly are not. Given the current snowpack, it is nearly impossible to tell which steep slope could produce a dangerous avalanche.

    The key message is this: on steep, open, or sparsely treed slopes above 5,000 feet, it is possible to trigger a 1–3 foot thick persistent slab that could propagate widely and be large enough to bury or seriously injure you. These avalanches can also be triggered from connected lower-angle terrain above, below, or adjacent to steep slopes.

    Heed obvious signs of instability such as whumpfs or shooting cracks, but recognize that none of the recent avalanche involvements reported these warning signs before release. The safest assumption is that any steep slope may harbor unstable snow, and travel decisions should reflect that uncertainty.

    You can reduce your risk by choosing low-angle terrain and minimizing time spent on, under, or next to steep slopes. If you venture into steeper terrain, seek simple slopes with clean runouts free of trees, cliffs, or gullies—recognizing that these options are limited in our area. Travel one at a time in avalanche terrain and plan up-tracks to avoid exposure to potential slide paths.

    (1/11/2026)

    This small avalanche was remotely triggered by riders in the sidecountry east of WMR. This likely failed on weak snow above the Christmas Crust. While this slide was small, two others in recent days were plenty big enough to bury, injure, or kill a backcountry traveler.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    This is an if/then type of problem: if the sun comes out for a sustained period, then wet loose avalanches are likely, especially on slopes that haven’t seen much sun over the past few days. Cloud cover is difficult to forecast, but you can be your own avalanche forecaster for this problem today.

    Sun on the snow is your cue to reassess. If slopes above or around you are heating up, expect surface snow to start shedding, so adjust by moving to shadier aspects or lower-angle terrain. Falling snow from trees, rollerballs, pinwheels, and damp surface snow are all signals that wet avalanche problems are ramping up. Keep in mind that rock bands, cliffs, and upper start zones often warm before the snow below your feet or machine, and small wet loose avalanches can grow quickly and be dangerous in terrain traps.

    (2/5/2025)

    Wet loose activity on a steep and rocky southerly slope. 

    Photo: Flathead Avalanche Center

Avalanche Discussion

Despite minimal loading over the past five days, there have been four human-triggered slides on a buried weak layer since January 7th—two of them remotely triggered. We also received an image from Six Mile Drainage in the Swan Range of a snowmobile-triggered avalanche that may have failed on a buried weak layer.

If you look around the WMR sidecountry—or other heavily used areas (i.e., Noisy Basin)—you’ll likely see many tracks on steep slopes but few obvious signs of avalanches. My hunch is that this may have more to do with the spatial variability of the slab/weak layer/crust combination rather than the reactivity of the problem. In other words, multiple remote triggers outside of a loading event show that even though this problem is difficult to find, it can be surprisingly reactive when you do. That makes me hesitant to “assess” my way onto steep open slopes right now.

All reported human-triggered slides on this layer have occurred near WMR (except potentially for Six Mile in the Swan), though similar snowpack structures exist elsewhere. It’s possible the problem is localized, or simply that higher use has made it easier to observe near the resort. It’s reasonable to assume slightly higher danger near WMR, while also being on alert in other zones.

With that in mind, Rob, Mike, and I visited Aeneas Ridge on Sunday. We saw no signs of instability and got non-propagating test results, yet we closed all steep open slopes and chose safe uptracks, descending one at a time through short, disconnected pitches. That’s where our risk tolerance is right now.

It may not be a likely event, but I just can’t figure out where this problem is and isn’t, so I’m going for low-angle terrain, or short disconnected pitches with clean runouts.  

Wind Slab: Wind continues to blow, but most zones are blown out, and additional transport is minimal. If you head into the higher elevations, continue to evaluate leeward slopes that show fresh evidence of wind-affected snow. 

Abgedeckte Regionen