Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Friday, March 23rd at 7:00 a.m. Today’s advisory is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp in partnership with Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
A warm and wet storm impacted the advisory area overnight. The mountains around Big Sky and West Yellowstone received 5-7” of high density snow above 8,000 ft. and rain at lower elevations. Cooke City picked up 2-4” of high density snow while the mountains around Bozeman saw mostly rain. This morning, the moisture has turned off and temps have dropped freezing above 8,000 feet. Winds are blowing 5-20 mph out of the W-SW. Today, there is a slight chance for rain and snow showers in the mountains, but significant accumulation is not expected. Temps will warm into the upper 20’s to mid-30’s F and winds will remain light to moderate out of the W-SW. Another round of moisture moves into the area tonight and tomorrow. The mountains south of Bozeman could see 1-3” by tomorrow morning.
Yesterday, both wet and dry avalanches were observed. Skiers outside of Cooke City saw multiple wind slabs that failed naturally near upper elevation rock bands (photo). The same group saw wet loose avalanches later that afternoon. A similar set up will exist today with 4-7” of new snow at upper elevations and rain down low.
Winds slabs and dry loose avalanches will be most prominent on steep slopes above 8,000 feet. Watch for areas of wind drifted snow below upper elevation ridgelines and rock bands. Cracking/collapsing and recent avalanches are obvious clues the snow is unstable. Avoiding wind loaded slopes by making conservative terrain choices will be the best defense against trigging slides today.
At mid to low elevations, wet snow avalanches will be a major concern. Rain on snow overnight will create dangerous avalanche conditions on steep slopes below 8,000 feet. Keeping slope angles below 35 degrees and avoiding terrain traps such as creek beds and gullies will be essential for safe riding at mid to low elevations.
Today, the dry snow avalanche danger is rated CONSIDERABLE on wind loaded slopes above 8,000 feet and MODERATE on non-wind loaded slopes. The wet snow avalanche danger is rated CONSIDERABLE on steep slopes at mid to low elevations.
The mountains around Bozeman picked up plenty of moisture out this storm, but most of it fell as rain. The Alpine weather station at Bridger Bowl is recording .7” of moisture totaling 1” of snow. That is not a good ratio for powder skiers. That means most of the precipitation fell as rain, which will create dangerous wet snow avalanche conditions in the Bridger Range. Similar conditions exist in the northern Gallatin Range.
Shower Falls Snotel site has not dropped below freezing in 48 hours, which means free moving water is impacting the upper layers of the snowpack creating unstable conditions. Yesterday, ice climbers in Hyalite observed a large wet loose avalanche pour over the Scepter, a very popular ice climb (video). Fortunately nobody was on the climb when the slide occurred. Today, I would steer clear of steep-gullied ice climbs and avoid skiing or riding slopes steeper than 35 degrees, primarily in mid to low elevation terrain (photo).
On the highest peaks around Hyalite, it will be possible to trigger dry snow avalanches on steep, wind loaded slopes. On Wednesday, a skier triggered a pocket of wind drifted snow that could have been dangerous if triggered in high consequence terrain (video). If you’re skiing or riding the upper peaks in Hyalite, approach all wind loaded slopes with caution.
Today, dangerous wet snow avalanche conditions exist and the avalanche danger is rated CONSIDERABLE on all slopes below 8,000 ft. In alpine terrain where temps have dropped below freezing, the dry snow avalanche danger is rated MODERATE on wind loaded slopes and LOW on non-wind loaded slopes.
If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Cornice Fall, Centennial Mountains, ID
On Tuesday, March 20, a snowmobiler walked to edge of the ridge and broke a cornice. He tumbled to the bottom and was injured and air evacuated out (photo). A report of the accident is HERE.
Send us your observations on Instagram! #gnfacobs
Posting your snowpack and avalanche observations on Instagram (#gnfacobs) is a great way to share information with us and everyone else this spring.
Cooke City is buried with snow this winter. Sam Wilson of the Billings Gazette wrote an article on the potentially record busting season (article).