Photos

"One small slide on a N asp at head of Bacon rind creek, elev 8750,  had a crisper look than most of the others observed, suspect more recent." Photo: M. Best

A snowmobiler triggered this small avalanche on Friday (1/11) between the 3rd Yellow Mule and McAtee Basin on Buck Ridge. The slope has a terrain trap at the bottom where snow can pile deep and makes small slides more dangerous. The relatively shallow snowpack is weaker and shows that a poor snowpack structure exists on some slopes in the northern mountains of our advisory area, and makes avalanches possible to trigger. Photo: GNFAC

Avalanche triggered by snowmobilers in the Little Belts on Thursday (1/10). This is outside of our advisory area, but shows many of the mountains in Montana have a weak and unstable snowpack. Photo: N. Boyer

Avalanche triggered by snowmobilers in the Little Belts on Thursday (1/10). This is outside of our advisory area, but shows many of the mountains in Montana have a weak and unstable snowpack. Photo: N. Boyer

Avalanche triggered by snowmobilers in the Little Belts on Thursday (1/10). This is outside of our advisory area, but shows many of the mountains in Montana have a weak and unstable snowpack. Photo: N. Boyer

A rider experienced cracking on the edge of their tracks in Cabin Creek in the southern Madison Range. This is a sign of a poor, unstable snowpack structure. Photo: M. Lanterman

From e-mail: "We dug our pit upon crossing into the northern aspect of Twin Falls Basin. We had observed a few, small avalanches across the basin on Mount Bole and decided to dig a pit before skiing the northern aspect. We observed an ECTP 17 and decided to cross back over the ridge and ski out the rather sun crusted south facing aspect. Very faceted snow and large wind slabs were observed during the entire tour." Photo: M. Beck

A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.

A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.

A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.

A snowmobiler triggered this avalanche on Friday afternoon (1/11) on Mt. Abundance north of Cooke City. It broke into old snow, and is on a south aspect at 10,000'.

This graph shows snow water equivalent (SWE) by date at the primary SNOTEL sites that we use in the GNFAC region. From October 1st, 2018 to January 12th, 2019. Steeper lines indicate bigger storms and flatter lines indicate periods of little to no snow. A large storm at the beginning of Novermber laid down a 1-3 foot base. Relatively dry and cold weather through November caused much of that snow to become weak. This weak snow was buried by a series of storms. Avalanches were seen during and following many of these storms. During dry weather between storms, more weak layers formed on the surface of the snowpack and were subsequently buried. (Graph created by GNFAC from NRCS provisional data).

One of many avalanches that broke during the last week's avalanche cycle at Lionhead. Natural and snowmobile triggered slides were reported between 1/7 and 1/9/19. On 1/6-1/7 the area got a foot of heavy snow followed by strong winds. This loaded an unstable snowpack that is poorly supported by 1.5' of sugary snow on the ground. Avalanches broke 2-3 feet deep on this weak snow, and propagated relatively wide. Photo: GNFAC

One of many avalanches that broke during the last week's avalanche cycle at Lionhead. Natural and snowmobile triggered slides were reported between 1/7 and 1/9. On 1/6-1/7 the area got a foot of heavy snow followed by strong winds. This loaded an unstable snowpack that is poorly supported by 1.5' of sugary snow on the ground. Avalanches broke 2-3 feet deep on this weak snow, and propagated relatively wide. Photo: GNFAC

A snowmobile triggered avalanche that broke during the last week's avalanche cycle at Lionhead. Multiple (5+) natural and snowmobile triggered slides were reported between 1/7 and 1/9. On 1/6-1/7 the area got a foot of heavy snow followed by strong winds. This loaded an unstable snowpack that is poorly supported by 1.5' of sugary snow on the ground. Avalanches broke 2-3 feet deep on this weak snow, and propagated relatively wide. Photo: GNFAC

A snowmobile triggered avalanche that broke during the last week's avalanche cycle at Lionhead. Multiple (5+) Natural and snowmobile triggered slides were reported between 1/7 and 1/9. On 1/6-1/7 the area got a foot of heavy snow followed by strong winds. This loaded an unstable snowpack that is poorly supported by 1.5' of sugary snow on the ground. Avalanches broke 2-3 feet deep on this weak snow, and propagated relatively wide. Photo: GNFAC

A snowmobile triggered avalanche that broke during the last week's avalanche cycle at Lionhead. Multiple (5+) Natural and snowmobile triggered slides were reported between 1/7 and 1/9. On 1/6-1/7 the area got a foot of heavy snow followed by strong winds. This loaded an unstable snowpack that is poorly supported by 1.5' of sugary snow on the ground. Avalanches broke 2-3 feet deep on this weak snow, and propagated relatively wide. Photo: GNFAC

Skiers found a variable snowpack near Frazier Basin in the northern Bridgers. This south-facing slope had a foot of facets near the ground, which was not present on a nearby northern aspect. Photo: Unknown

Skiers observed collapsing on Weber Mountain near Lick Creek in Hyalite. They dug a pit and found poor structure with a thin, faceted snowpack and got poor stability test results, with ECTP6 failing on a thick layer of facets. Photo: M. Talty

In Cabin Creek (1/10/19) we found a recently buried layer of surface hoar as well as the weak, sugary snow that makes up the bottom 1.5' of the snowpack in the southern ranges. Avalanches are possible to trigger on the sugary facets near the ground. Both of these weak layers will persist and cause avalanches when we get more snow and wind loading. Photo: GNFAC