Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Monday, March 13th at 6:30 a.m. Today’s advisory is sponsored by Mystery Ranch and the Yellowstone Club Community Foundation. This advisory does not apply to operating ski areas.
The mountains did not receive any new snow since yesterday morning. West to northwest wind yesterday gusted to 40 mph. This morning, wind is westerly at 15-25 mph with gusts of 30-40 mph and temperatures in the 20s F. Under mostly cloudy skies today, temperatures will reach high 30s to 40 F with westerly wind at 15-25 mph. Light snow tonight could produce 1-2” by morning. Looks like rain tomorrow with next chance for snow Thursday.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Strong west to southwest wind through the last week drifted new snow into slabs that are possible to trigger today. These slabs range from 6 inches thick in the mountains near Bozeman to 6 feet thick near Cooke City. The most suspect slopes are below ridgelines and near large cornices. Yesterday my partner and I skied Saddle Peak in the Bridger Range where we found good stability and were extra cautious of recently wind loaded slopes. Small wind slabs have high consequences in terrain above cliffs or trees.
Cornices are massive and sensitive to the weight of a skier or rider (video, photo). On Thursday at Lionhead, Doug and I encountered a snowbiker minutes after his machine “just got swallowed up” when a huge cornice collapsed beneath him (video). This was the second of three groups last week that triggered cornices from the ridgeline above (photo). Warm temperatures will make cornices easier to break. Yesterday a skier in Hyalite had a very scary encounter when they fell into a hole behind a cornice where it had crept away from the earth below (photo). Be extra cautious on slopes below cornices and stay far from the edge of ridgelines. Travel close to the scoured and non-loaded (windward) side of ridgelines, and stay away from the opposite (leeward) edge unless you are absolutely sure it is not an overhanging cornice.
Avalanches were easily triggered and ran naturally over the last week, and are possible to trigger today. Our photo and video pages show recent avalanches were confined to wind loaded slopes and layers of new snow, which will quickly gain strength. Widespread buried weak layers are not a concern, but we must carefully assess the snowpack if we choose to venture to steeper, more complex, and higher consequence terrain.
Today, avalanche danger is MODERATE on wind loaded slopes and LOW on non-wind loaded slopes.
Clouds today will minimize wet snow avalanche danger. If the sun shines, snow on sunny slopes will quickly become damp and make wet loose avalanches likely. This time of year snow conditions change fast with a variety of weather. Continuously assess the snowpack throughout the day. A skier on Saddle Peak yesterday noted significant changes in snow quality over a short time between laps.
Doug will issue the next advisory tomorrow morning by 7:30 a.m.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.
Beacon Training Park at Beall: Open and free to the public for avalanche beacon practice seven days a week from 9 a.m. to 8 p.m., southeast corner of Beall Park in Bozeman (photo).