Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

Enjoy today's fast travel conditions and generally stable snowpack. Warming temperatures may initiate thin wet loose slides in Thursday's fresh snow. Give corniced ridgelines a wide berth while traveling along or beneath. 

Avalanche problems

  • Cornices

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

    Prominent wind-formed features along ridgelines are strengthening but require prolonged below-freezing temperatures to stabilize. Limit your time traveling on slopes below cornices where a large chunk of snow could calve off and threaten you. While traveling along ridgelines, keep far back from the edge as they extend further from the solid ground than expected.

    (3/28/2022)

    Warm temperatures have weakened cornices. This one in John F. Stevens Canyon failed Sunday, 3/27. The debris ran over 1000 vertical feet and entrained wet snow as it descended.

    Photo: Adam Clark/BNSF

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Thursday's 1-4 inches of new snow and graupel is resting on a slick crust. As today warms up, anticipate thin wet loose slides to develop. These should be small and harmless but could surprise you in long-running gullies or terrain traps. Precursors to this problem will be snow falling off or melting from tree branches and rollerballs forming on steep slopes. Sustained April sunshine can rapidly change the surface snow. Move to a different aspect before the new snow begins to moisten. You have identified this problem if you can make a snowball with the fresh snow.  

    (3/31/2022)

    An extended warming event produced wet loose avalanches on northerly aspects. This slide is classified as D1.5 on the destructive scale.

    Photo: Mark Dundas

Avalanche Discussion

Thursday's cool weather was a welcome respite from a long-lived period of above-average temperatures. As of 0400 Friday morning, mid-elevation weather stations have been below freezing for around 34 or more hours. This is the most prolonged period of winter-like temperatures since March 21. Low elevation stations report readings below 32F since yesterday evening. Today's highs are forecast to creep above the freezing mark at 6500 feet and approach 50F on the valley floor.

The extended period of below-freezing temperatures locked up the snowpack and allowed us to drop the avalanche danger to LOW Thursday. Yesterday's observations reported that snow was firm, and difficult surface conditions thwarted one party's effort in the northern Whitefish Range. I visited the Middle Fork and found a surface crust 6-8 inches thick on north and south-facing slopes at 6000 feet. The mid-elevations surface stayed supportable throughout the day and made for loud turns with trouble keeping an edge.

We have removed Wet Slab from today's problem list. The cold temperatures and thick surface crust have shut down meltwater production, working through the snowpack. We are keeping the cornice problem for another day or two due to uncertainty about how well their roots have refrozen. The wet, loose slides have made a return appearance due to Thursday's snow and today's expected warming temperatures. Snow returns to the Flathead on Saturday with moderate to strong winds. A dry snow avalanche problem may return with thin wind slab development.

 

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