GNFAC Avalanche Forecast for Sat Mar 20, 2021

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Saturday, March 20th at 7:00 a.m. Today’s forecast is sponsored by Upper Yellowstone Snowmobile Club and The First National Bank of Gilbert (Minnesota). This forecast does not apply to operating ski areas.

Mountain Weather

This morning the mountains near Bozeman, Big Sky and West Yellowstone have 6-8” of new snow with 2” near Cooke City. Temperatures are 20s to low 30s F and wind is west-southwest at 5-15 mph. Today temperatures will be 20s to low 30s F with west-northwest wind at 5-15 mph. Steady snowfall could deliver 3-6” by this afternoon, and another 5-8” by tomorrow morning with potentially more near Cooke City and West Yellowstone.

Snowpack and Avalanche Discussion

The first day of spring feels like a return to winter. This morning there is 6-8” of new snow equal to 0.6-0.8” of snow water equivalent (SWE) near Bozeman, Big Sky and West Yellowstone with steady snowfall expected today. The new snow fell onto weak, sugary snow on some slopes and crusts on other slopes. These interfaces make large avalanches of the new snow easy to trigger and may cause slabs to break wide and run long distances. Yesterday Doug saw the weak snow on the surface in the Centennials (outside our advisory area, but similar snowpack) and explains why it is a concern in his video (Doug’s video, photo). Doug was snowmobiling with Mark Staples, director of the Utah Avalanche Center, who appears in Doug’s video and discusses terrain to watch out for, such as steep slopes up high and confined gullies where sliding snow can pile up deep.

Carefully assess the stability of the new snow before riding or crossing steep slopes. Expect stability to decrease through the day with continuous snow, and choose simple, less consequential objectives. Today, continued snowfall on top of weak layers and crusts makes human triggered avalanches likely and natural avalanches possible. The avalanche danger is rated CONSIDERABLE.

In the mountains near Cooke City snowfall totals are less than elsewhere, but they should catch up or surpass other places by tomorrow morning. Doug was riding near Cooke City on Tuesday and found weak layers on the surface, similar to elsewhere, that are now buried by new snow (video). This morning a couple inches of new snow will create minimal instability, but this afternoon will be different. Heavy snow today could pile up quickly and create slabs that easily slide on the old snow surface. Expect stability to decrease through the day, and carefully evaluate the stability of the new snow before riding steep slopes. Watch for cracks breaking across the snow surface under your sled or skis as one sign the new snow is becoming unstable. Today avalanches of new snow are possible to trigger 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! March 20, 5:30 p.m., Snowpack Update for Bozeman Splitfest, online Link to Join HERE

March 24, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE

March 29, 6 p.m., Free 1-Hour Avalanche Awareness, online Link to Join HERE

April 5, 6:30 p.m. Forecaster Chat, online hosted by Uphill Pursuits, “Spring Snowpack and forecasting tools”.

The Last Word

Bears. Grizzly bears. They are waking up, stretching their limbs and looking for food. Walking the aisles in Safeway puts you on top of the food chain; when you are in the backcountry, they are. Carry a beacon, shovel, probe...and bear spray. Bozeman Daily Chronicle article.