GNFAC Avalanche Forecast for Fri Feb 19, 2021

Not the Current Forecast

Good Morning. This is Ian Hoyer with the Gallatin National Forest Avalanche Forecast on Friday, February 19th at 7:15 a.m. Today's forecast is sponsored by Blitz Motorsports and Yamaha and Advanced Innovation. This forecast does not apply to operating ski areas.

Mountain Weather

One to 3” of new snow fell overnight across most of the advisory area, with the area south of Big Sky picking up 5-6”. Winds around Bozeman and Big Sky are 25-30 mph out of the south and west, with 40-50 mph gusts. Winds are a bit lighter near West Yellowstone and Cooke City. Temperatures this morning are in the single digits and teens F and will rise into the teens and low 20s F today. Winds will continue out of the south and west, with the peak gusts moderating a little. Periods of snowfall today and tonight will deposit 2-4” by tomorrow morning around Bozeman and Big Sky and 4-8” near West Yellowstone and Cooke City.

Snowpack and Avalanche Discussion

Strong winds yesterday drifted the abundant fresh snow and continued to load many slopes. Around noon yesterday, an avalanche broke naturally, several feet deep, on a heavily wind-loaded slope in the Bridger Range, south of Saddle Peak (photo). With a bit more new snow and continued winds, similar slides will be easily triggered today, especially on wind-loaded slopes. Avalanches that initially break beneath the new and wind-drifted snow will likely step down to the lower weak layers, mid-pack or near the ground. 

Continued snowfall may obscure subtler signs of wind-loading, but be especially skeptical of slopes beneath cornices and those with large drifted pillows directly below ridgelines. Avoid travelling on, or beneath, slopes steeper than 30 degrees. Conservative decision making is essential today. With natural avalanches possible and human triggered slides likely, the avalanche danger is rated CONSIDERABLE.

With a similar weak snowpack structure in the southern ranges, the consequences of triggering a slide are the same as up north, but without as much new snow the likelihood is a bit less. A large snowmobile triggered slide in Cabin Creek is a good reminder of the sort of slide we’re worried about (details). With large, deadly avalanches a real possibility, avoiding all avalanche terrain is a very reasonable strategy. If you are going to poke on to steeper slopes, dig a snowpit and do some snowpack tests before committing and then only expose one person at a time. The avalanche danger is MODERATE today.

Around Cooke City, the primary concern is avalanches breaking on wind-loaded slopes. A snowmobile triggered slide yesterday on Crown Butte highlights this concern (photo, photo). More snowfall and wind today will create fresh drifts on top of the older drifts and you could trigger either. Dave was in Cooke City the last few days and is cautiously optimistic about the strength of the lower snowpack, but didn’t rule out the possibility of triggering a deeper slide if you hit an atypically thin spot (Wednesday video, Thursday video). For today the avalanche danger is rated MODERATE.

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

BEEHIVE BASIN AVALANCHE ACCIDENT REPORT

We posted a detailed report from Sunday's fatal avalanche in Beehive Basin here

The video of our accident investigation from the field is here.

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:

Every Saturday in Cooke City, FREE snowpack update and rescue practice at the Round Lake Warming Hut between 10 a.m. and 3 p.m. Poster with More Info.

February 22, 6-7 p.m., Forecaster Chat: Rethinking Avalanche Terrain from a Strategic Perspective, Hosted online by Uphill Pursuits, Link to Join HERE

The Last Word

A snowboarder died yesterday in an avalanche that broke 5’ deep in a ravine just off the highway on Togwotee Pass outside Jackson, WY (news article). This is the 20th avalanche fatality in the US this February.