Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

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

Pay attention to today's snowfall totals as the day progresses. You could trigger a slide on slopes where the wind has stiffened the surface or formed drifts. Thin, loose slides may develop on steep terrain in areas sheltered from the wind.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Developing light snowfall and southwest winds may form thin slabs of wind-drifted snow later today. We expect these to be confined to upper-elevation leeward slopes, but if snowfall exceeds forecasted totals, you may encounter them at mid-elevations. Wind features will form along and beneath ridgelines and further down the slope near ribs and gulleys. Slabs may form on crusts or faceted weak surface snow, adding to their instability.

    Blowing snow, textured surfaces, and smooth pillows should help identify these features. Cracking in the snow beneath you or your machine indicates an instability directing you to terrain sheltered from the wind. 

    ADDITIONAL DISCUSSION: Natural and human-triggered loose snow slides may occur on steep slopes in areas sheltered from the wind this afternoon. These will most likely develop where the new snow falls onto a surface crust which may inhibit bonding. 

    (3/2/2023)

    A shooting crack in a wind slab immediately below a saddle.

    Photo: md

Avalanche Discussion

Pacific moisture moves into the Northern Rockies today, but unfortunately, most of the snowfall will remain south of our area. The mountains around Bozeman are under a Winter Storm Warning with 1-3 feet of snow expected, while the mountains around Missoula are under a Winter Weather Advisory. Storms tracking to our south generally favor the Swan Range; this one is no exception, with 4-6 inches possible by day's end. Totals in the Whitefish Range, the Flathead Range, and southern Glacier Park are forecast to be a mere 1-3 inches.

We have added Wind Slab to the problem list for the Swan, where this problem may develop this afternoon if snowfall arrives as forecast. The avalanche danger has bumped up to MODERATE in this range. If snowfall exceeds forecasted totals in other ranges, a wind slab and loose snow problems may develop but should remain small and harmless.

Today's overcast skies and light snowfall are a change from the generally dry, sunny conditions we've experienced over the past 12 or so days. Cooler weather and cloudy skies will limit warming at the surface and end the string of days where wet loose instabilities were on our radar. This weather resulted in a crust on most sunny aspects reaching 7000 feet or higher, extending onto northwest and northeast aspects in places.

Prolonged periods of cold overnight temperatures limited the size and distribution of wet loose activity since March 12. Slides were mostly size D1 -D2, and few gouged into the underlying weak snow. All in all, an uneventful wet-loose cycle. This has been documented through the numerous public observations and yesterday in photos from an overflight of the Flathead Range (Observation) and Sarah's field day in Rescue Creek (Observation). 

Snow totals for the 2022-23 season are underwhelming. We would be in a rough spot if not for the much cooler-than-average temperatures. The summit of the WMR ski area is reporting 203" so far. Compare that to the Mammoth Mountain ski area in California's Sierra Nevada, where well over 800 inches have fallen at their summit and around 650 inches at their base lodge. This triple dip La Nina favored most of the western US except for the northern portions of Washington, Idaho, and Montana.

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.

 

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