Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Fri
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

Warm temperatures will weaken surface snow as the day progresses. A falling cornice caused a large avalanche on a buried weak layer yesterday (Wednesday). Choose slopes free from overhead hazards and seek out shaded terrain if you begin to sink into the slushy surface snow.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Yesterday (Wednesday), forecasters intentionally triggered a large, hard-slab avalanche that failed on buried weak layers in the central Whitefish range (photo above/right). This avalanche required the weight of a tumbling cornice to fail and is a reminder that it is still possible for natural or human triggers to cause a slide. 

    Avalanche activity on buried weak layers have been confined to aspects NW-NE-SE at mid- and upper-elevations in the Flathead Range and southern Glacier National Park. In the Whitefish Range, documented activity has been at upper elevations. Several notable weak layers have demonstrated their ability to produce large avalanches this season, including facet/crust combinations formed in late December and mid-January, as well as basal facets and depth hoar formed in November. 

    Here are a couple of suggestions to reduce your exposure to this hazard:

    • Choose slopes with a uniform and deep snowpack
    • Steer around likely trigger points, including convexities or slopes speckled with rocks
    • Give cornice a wide berth and don’t linger below corniced ridges, particularly during the warmest parts of the day
    • Choose lower-angle terrain

    (3/22/2023)

    Cornice fall triggered a Hard Slab that failed on a persistent weak layer. This avalanche occurred on a north aspect at 7100 feet. 

    Photo: Cam

Avalanche Discussion

The transition from winter to spring has been well-documented over the last week. Many mid-elevation weather stations have seen temperatures cycle above freezing during the heat of the day and below overnight over the previous seven days. During this time, we've seen all the typical harbingers of spring: tumbling cornice, frowning glide cracks, and diurnal Wet Loose activity. At a glance, it might seem like we're well into the spring rhythm. However, a wider lens reveals that we can still find winter if we look in the right places. 

Weather stations above 7000 feet (like Aeneas in the Swan Range or Link Mt in the central Whitefish) crept above freezing for the first time yesterday, and many observations still report dry snow on shaded aspects. Spring hasn't quite taken control in these areas, and a cold front arriving later today will buy more time for these strongholds of winter. If you're searching for powder riding, be attentive to surface conditions since Wet Loose activity can develop rapidly when dry snow transitions to moist for the first time. Rollerballs and pinwheels are precursors to Wet Loose slides and should persuade you to relocate or exit early. 

Buried weak layers are another lasting legacy from this winter. Our most recent evidence of this lingering problem occurred yesterday when Cam and Guy used a cornice to intentionally trigger a large, hard-slab avalanche in the central Whitefish Range. This slide demonstrates that triggering an avalanche on weak layers is becoming more difficult–but not impossible. 

FOFAC Event: March 30th, 2023– Whether you're chasing tan lines, big lines, or both, you'll learn something valuable from FAC Lead Forecaster Mark Dundas about spring avalanche problems, how they differ from winter problems, and how to manage them. We will also discuss current conditions and concerns (or lack thereof!) with our spring snowpack. Enjoy a cold brew from Bias Brewing and a scoop from Sweet Peaks Ice Cream. The event is free and open to everyone. Begins at 6 pm.

FOFAC Recording March 15th, 2023-- Cam's State of the Snowpack link here

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