Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, April 4 at 7:30 a.m. My wife and two sons, who make this and every advisory possible, are the sponsors of today's advisory. This advisory does not apply to operating ski areas.
This morning mountain temperatures were in the teens F. Near Bozeman ridgetop winds were blowing 10 mph gusting 20 mph from the SW. Near Big Sky ridgetop winds were blowing 20 mph gusting 30 mph from the SW. Today will have sun in the morning and increasing clouds this afternoon. High temperatures should be in the low 30s F and winds may increase a little this afternoon. Snow should fall tonight but only an inch or two should accumulate.
Bridger Range Gallatin Range Madison Range
Cooke City Lionhead area near West Yellowstone
What about facets near the ground? They were definitely stressed by a heavy load of snow five days ago when 2 feet of heavy snow fell in many places. One large avalanche breaking near the ground was observed on Mt Blackmore just south of Bozeman last Saturday. Since then no others have been triggered or seen. The odds of triggering a similar slide have decreased and are pretty low at the moment but not zero. If riding in avalanche terrain today, decrease those odds even further by avoiding rock outcrops or any thin part of a slope. These spots are good trigger points where a fracture can initiate then propagate into deeper areas.
The main problems are only a foot or so deep. Near Big Sky in Beehive Basin skiers on Wednesday triggered several small avalanches on surface hoar buried less than a foot deep (photo from Monday before it was buried). In the northern Bridger Range yesterday, skiers found a few places where graupel (like hail) had pooled and was buried (photo). Some isolated wind slabs and pockets of this graupel were their main concerns. This time of year shallow instabilities come and go very quickly.
For today, watch out for specific slopes that may have one of these shallow weak layers or fresh wind slabs from increased winds overnight. Slopes steeper than 35 degrees have a MODERATE avalanche danger. Avalanches are unlikely on less steep slopes where the danger is LOW.
Cornices: Cornices are growing at a fast rate and are getting quite enormous this season. They can break with a passing skier and deserve a wide berth. A falling cornice can also be a very good trigger for deep slab avalanches.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.
Our last daily avalanche advisory will be this Sunday, April 6. If conditions warrant we will issue intermittent advisories the following week.