GNFAC Avalanche Forecast for Sun Apr 4, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, April 4th at 7:00 a.m. Today’s forecast is sponsored by Blitz Motorsports and Yamaha and Bridger Bowl. This forecast does not apply to operating ski areas.

Mountain Weather

This morning temperatures are mid 30s to low 40s F and wind is westerly at 10-20 mph with gusts to 35 mph. Today, under partly sunny skies, temperatures will reach 40s and 50s F with west wind at 15-25 mph. Weather will be different tomorrow with colder temperatures and possible snow for a couple days.

Snowpack and Avalanche Discussion

All Regions

Today is the third consecutive day with temperatures starting above freezing. Last night the snow surface re-froze only slightly, if at all, on slopes that were wet yesterday. Avalanche danger will increase as soon as frozen crusts melt, and wet loose avalanches will be possible to trigger. By early afternoon, on steep, sunny slopes expect wet avalanches that involve the top 4-6” of snow. These wet loose slides are fairly predictable and relatively small, but they can be deadly in the wrong terrain and may become large. Yesterday skiers in the northern Bridger Range saw a natural wet loose avalanche that ran far and entrained enough snow to bury or injure someone (photo). We skied near this area earlier in the day and saw similar natural slides from prior days (photo). We found a supportable crust in the morning on most slopes, except high-elevation northerly facing slopes where the snow was dry and generally stable. Slopes with a crust became wet by late morning and the top few inches were starting to slide (video).

Wet slab avalanches are not expected to be widespread, but they are difficult to predict and can be destructive and deadly. Slight freezes over the past few nights have been enough to hold off wet slabs, but each day of warm temperatures allows water to flow deeper into the snowpack and increases the chances for wet slab avalanches (wet slab video). The strategy to avoid wet slabs is the same as avoiding wet loose avalanches. Make a plan that avoids riding on and underneath steep slopes too late in the day, before the snow surface melts and gets wet. If you notice the snow did not freeze last night, avoid steep slopes from the start. Signs that the snow is wet enough to avalanche include: pinwheels of sticky snow rolling down slopes, natural loose snow slides, and sinking deeper than your boot in wet snow when you step off your skis or snowmobile (wet snow timing video). Today, large wet snow avalanches are possible and the avalanche danger is MODERATE.

If you get out, please send us your observations no matter how brief. You can submit them via our website, email (, phone (406-587-6984), or Instagram (#gnfacobs).

Upcoming Avalanche Education and Events

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events and opportunities to check out:

TOMORROW NIGHT! April 5, 6:30 p.m., Forecaster Chat with Alex Marienthal, hosted by Uphill Pursuits, “Spring Snowpack and Forecasting Tools”. Link to Join.

The Last Word

We will end regular forecasts next weekend, but avalanches will still be possible through April or longer. Join me tomorrow night for an online talk about strategies and tools to stay safe this spring. April 5, 6:30 p.m. Link to Join.

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