Good morning. This is Ian Hoyer with the Gallatin National Forest Avalanche Forecast on Friday, March 18th at 7:15 a.m. This information is sponsored by Blitz Motorsports and Yamaha and Yellowstone Club Community Foundation. This forecast does not apply to operating ski areas.
There is no new snow this morning. Temperatures are in the teens and low 20s F. Winds are 5-15 mph out of the south and west, with gusts up to 30 mph. There will be a few snow flurries this morning, before clouds clear and it becomes partly sunny this afternoon. High temperatures will range from the high 20s up to 40 F. Moderate southwesterly winds will continue today. The next chance for significant snowfall is on Sunday.
Avalanches breaking on weak layers buried 1-3 ft deep are the primary concern today. After the snowfall earlier this week, most slopes now have a cohesive slab above several weak layers in the upper snowpack. These weak layers formed on almost all slopes during the extended dry spells over the last two months. The thickness of the slab above them varies a bit, around Cooke City the slab tends to be a little thicker (2-3 ft deep), while in many other areas it is somewhat thinner (1-2 ft deep), consisting just of this last week’s new and wind drifted snow. The unifying factor is that we now have strong snow over weak snow on most slopes (Buck Ridge video). This is exactly the recipe for avalanches and accordingly we’ve seen numerous slides triggered this week (avalanche log). Don’t be fooled by sunny skies or mild temperatures, it is still winter in the mountains and you could trigger a large, dangerous slide today. Recent avalanches have been breaking above riders and triggered from a distance, which makes them particularly dangerous (Wyoming Bowl video, Mt. Blackmore slide details). Carefully analyze the snowpack before getting onto steep slopes and be ready with rescue gear and a partner watching from a safe spot, in case you do trigger a slide. Unfortunately these weak layers won’t heal quickly, so plan to factor them into your terrain selection for the foreseeable future.
Temperatures today will rise above freezing in many areas (around five degrees F higher than yesterday). When the sun pokes through, expect to see shallow, wet loose avalanches. You could trigger them as well on steep slopes baking in the sun. Be mindful of these small slides in places where getting knocked off your feet would have big consequences.
With triggering large avalanches possible today, 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 (firstname.lastname@example.org), phone (406-587-6984), or Instagram (#gnfacobs).
Yesterday, March 17th, there were two avalanche fatalities in the western United States. A snowboarder was caught, buried and killed near Ophir, Colorado (preliminary report) and two skiers were caught and buried, with one passing away on the west side of the Tetons in Wyoming (preliminary information).