GNFAC Avalanche Advisory for Thu Feb 8, 2018

Avalanche Warning

It has snowed eleven out of the past twelve days around Cooke City and winds have been moderate to strong out of the west (weather log). The relentless combo of snow and wind has pushed many slopes past their breaking point. A large and destructive natural avalanche off Woody Ridge on Tuesday is a prime example of what’s possible (photo). A foot of snow overnight and more today will only make conditions more unstable. Until the snowpack gets a breather, the best option will be to avoid avalanche terrain including avalanche runout zones (photo).

Today, natural and human triggered avalanches are likely and the avalanche danger is rated HIGH on all slopes. 

Bracket Creek Snotel site in the northern Bridgers has picked up over 3” of snow water equivalent over the past four days. What’s unusual is Bridge Bowl has picked up roughly half that amount. The bottom line is – the sheer volume and weight of the new snow is putting a tremendous amount of stress on the snowpack. Wind loaded slopes will be the most prone to avalanches, but non-wind slopes remain suspect. We know the Bridger Range has a generally strong snowpack (video), but 3” of SWE in four days is enough expose any weakness. I wouldn’t be surprised if large natural avalanches occur, mainly in the northern part of the range. With more snow and wind on the way, the snowpack will remain on edge.

For this reason, the avalanche danger is rated CONSIDERABLE on all slopes.

Hyalite and Big Sky have received enough snow and wind to keep the avalanche danger elevated, mainly on wind loaded slopes. Overnight, winds blew 20-40 mph out of the west-southwest, which likely formed dense slabs in leeward terrain. Warm temps will keep wind slabs stubborn today, but they still can’t be trusted. These conditions also facilitate rapid cornice growth. Watch out for and avoid slopes beneath large cornices and give them a wide distance along the ridgelines.

Today, dangerous avalanche conditions exist on wind loaded slopes which have a CONSIDERABLE avalanche danger. Non-wind loaded slopes have a MODERATE avalanche danger.

The southern mountains haven’t received as much snow as the northern ranges. Carrot Basin Snotel site in the southern Madison Range is showing .4” of SWE over the past three days while Madison Plateau near West Yellowstone is showing .1” of SWE. Although snow amounts are less, buried surface hoar two feet deep and moderate to strong winds out of the west will present a few different problems today.

Watch out for wind loaded slopes near the ridgelines and avoid areas around large cornices. Also keep an eye out for surface hoar buried two feet deep. Yesterday, my partner and I rode in the Taylor Fork and got this layer to propagate consistently in stability tests (video). Doug and Alex also got unstable results on this layer near Hebgen Lake earlier in the week (video).

Wind loaded slopes and buried weak layers make human triggered avalanches possible and the avalanche danger is rate MODERATE.

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).