Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

A developing storm may increase the danger later today and overnight. You could trigger an avalanche in the new snow or where the winds have formed drifts or stiffened the snow surface. Fresh snow and wind may increase the chance of a slide on a deeper buried weak layer. Choose sheltered lower-angle terrain to enjoy today's refresh safely.

Avalanche problems

  • Wind Slabs

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

    New snow and shifting winds may form slabs of wind-drifted snow on various slopes. This problem will develop as the fresh snow piles up throughout the day and overnight. Winds from the east will drift snow onto westerly aspects this morning before the winds shift back to the west transporting snow onto easterly aspects this afternoon. Slabs will be thicker and more susceptible to triggering at upper elevations. Look for them near ridgelines and mid-slope terrain features like ribs and gullies. 

    Slabs may form on weak faceted snow, potentially propagating wider than expected. Blowing snow should develop, showing you which slopes are most dangerous. You've likely found a wind slab if the soft, light snow you're moving through suddenly becomes heavy (dense) or you run up onto stiff snow that supports your weight. Cracks shooting out from your skis or sled and collapsing the snowpack indicate the slab's instability. Choose terrain sheltered from the winds for a safer, more enjoyable experience.

    Additional Discussion: In areas sheltered from the wind, there is a chance a storm slab problem may develop this afternoon if snow totals reach 8 inches or more. This is most likely to occur during periods of increased precipitation intensity. Slabs will behave similarly to a wind slab with cracking signifying instability.

    (3/2/2023)

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

    Photo: md

Avalanche Discussion

This morning, a storm is moving into the area, with snow anticipated to develop after daybreak. Forecasted mountain SWE totals are generally around 0.5 inches for the Whitefish and Flathead Ranges, with up to 1.0 inches by tomorrow morning in the Swan Range. Winds will shift from east to west around noon before backing to the east after midnight. Temperatures this morning were generally 10-20 degrees warmer than yesterday. Temperatures will rise during the most intense snowfall this afternoon before crashing down as a cold front enters the area later today.

We will begin today with similar avalanche hazards and problems as yesterday, with LOW danger in the Whitefish, and Swan Ranges and MODERATE in the Flathead. The Persistent Slab is our only problem until enough fresh snow accumulates and new snow avalanche problems develop. Shifting winds initially form thin slabs on atypical aspects from this morning's easterly winds. A mid-day wind shift to a westerly flow will form slabs on NW-NE-SE aspects this afternoon and evening. Warming temperatures during this afternoon's snowfall may lead to instabilities within the new snow as denser snow falls onto less dense. A storm slab problem may develop in areas where the snow piles us 8 or more inches deep. Avalanche danger may peak later today or overnight during the most intense periods of snowfall. The Swan Range may reach CONSIDERABLE during this time frame.

A snowmobiler triggered a Persistent Slab avalanche  Wednesday in the northern Whitefish Range. This D2 Slab failed on an east aspect and had a crown depth of 18-24 inches. This is the first recorded human-triggered slide on buried weak layers in this range in many weeks. With loading anticipated on leeward slopes, we have bumped the likelihood of triggering a Persistent Slab to POSSIBLE in the Whitefish Range. We are keeping a POSSIBLE likelihood in the Flathead, where nearly all of the recent activity on this layer has occurred.

California is being impacted by its tenth Atmospheric River of the season while we, once again, settle for the relatively meager leftovers. The national avalanche center map shows many areas with HIGH and even EXTREME danger. Check out the Sawtooth Avalanche Center in Idaho, where heavy Pacific snow will overload a weak snowpack structure resulting in historic avalanches affecting valley floor infrastructure. On Thursday, NOAA's Climate Prediction Center (CPC) declared an end to the long-lasting La Niña that began nearly three years ago, signaling that ocean temperatures in the equatorial Pacific were warming up.

Thanks to Ted Steiner and Adam Clark with BNSF snow safety and volunteer Tom Whipple for returning to the Tunnel Ridge weather station to replace the wind sensor.

Fireside/Snowpack Wednesday, March 15. Join us for a virtual evening combining two favorite community ed workshops. FAC Forecaster Cam Johnson will kick things off with a State of the Snowpack presentation to help you digest the current conditions and plan your next trip. Then we'll shift to Fireside Chats for open dialogue about human and avalanche factors. A recreationist, forecaster, and avalanche educator all experienced a near miss in the first three weeks of February. Together, Kat, Cam, and Meg will explore the tough decisions, tricky snow, and lessons learned from their experiences. No registration is needed; click here for Zoom. The event will begin at 6 p.m. 

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