Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
Voir sur la carte

Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
Open full map
Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can still trigger a slab avalanche in both sheltered and wind-affected terrain. Loose snow sluffs are likely in steep terrain and may run naturally on sunny slopes. Limit your risk by reducing the time you spend traveling above terrain traps like gullies, cliffs, or exposed rocks and trees.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    The Swan and Flathead Ranges recorded up to a foot of snow in the last 48 hours. This snow fell on a crust on southerly aspects and weak snow on northerlies, adding to the instability. You may find slabs both where the wind has drifted the snow and in sheltered locations. Slabs will be thicker and stiffer at upper elevations downwind of ridgelines and saddles and on the sidewalls of gullies. 

    Cracking beneath you or your machine indicates a sensitive slab directing you to lower-angle terrain. Utilize hand pits and small test slopes to assess how the new snow is bonding to the older snow surface.

    (12/2/2023)

    Cracks like thses are clear signs the soft slabs near the snow surface are sensitive to a rider's weight and can be dangerous on larger slopes. 

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Riders continue to trigger sluffs on steep slopes holding 4-8+ inches of unconsolidated snow above a firm crust. Sluffs will be largest in terrain protected from the sun and wind, where this week’s snowfall remains dry and incohesive.  Sunshine this morning could trigger natural sluffs on southerly slopes. 

    Limit your time spent in confined, long-running gullies where you’ll have difficulty escaping a sluff. Choose descent routes free of terrain traps where moving snow could rake you through exposed hazards or pile up deeply. 

    If the sun hangs around longer than anticipated, expect surface snow to transition and run as wet loose, particularly at middle elevations. Rollerballs are a clear sign that the wet snow is primed to slide. 

    (12/24/2023)

    Note the descent path of the lookers right track. This type of descent allows your sluff from each turn to run next to you, vs. over you. 

    Photo: Pete Costain

Avalanche Discussion

As I review the weather and observations this morning, a theme emerges:  Winter is (kind of) back! Recent snowfall and seasonable temperatures have greatly improved the riding throughout the advisory area. However, in most cases, there is a prerequisite brush thrashing (obs 1, obs 2 , obs 3).

This was also the case during a FAC visit to Anna Creek on the East Side of the Swan Range. Throughout our travels, we noted generally unconsolidated snow resting on an impressively stout melt-freeze crust. We were able to kick off fast-running sluffs in extreme terrain on shaded slopes and found a cohesive slab in wind-stiffened snow at the entrance to a couloir. Both of these hazards were easily managed at the time, however, we acknowledged the potential for the faceting surface snow to become problematic once buried. Southeast aspects were particularly interesting as they harbored a crust/facet combination from warming Tuesday/Wednesday this week. Blase and Jeff noted this same structure East of WMR. This structure will be able to support a greater load and may result in larger avalanches once it reaches its limit. 

Upcoming event: Flathead Avalanche Friends Fest, February 21-24. Beacons & Brews, Name That Tune/Name That Avalanche, Workshop Night, Hot Dog Days, and Ultimate Après.  Check out 4 days of events: flatheadavalanche.org/event/friendsfest

Régions couvertes