Regional Conditions for Lionhead Range

This snowmobile was fully buried, along with its rider on February 7th, 2019, in the Centennial Range.

Photo of the snowmobile triggered slide that fully buried a rider on February 7th, 2019.

A large snowmobile triggered avalanche in the Gravelly Range (Outside of advisory area) on February 10th, 2019.

From email: "One rider was involved in the incident and was fortunate to be on the upper left side of the bowl when he saw the slide start. ... the crown was about 325 wide and varied in depth from 1 to 4 or 5 feet.  The ridge line was wind loaded and this was an issue we had discussed as a group and wanted to avoid.  We had read the reports for the day and knew that wind loading as well as a persistent week layer were both concerns. .... The rider involved entered the area from around where the road switchbacked and did not realize what was above him due to reduced visibility."

This avalanche broke on weak snow in the lower 1/3 of the snowpack after a storm dropped 2-3' of heavy snow between 2/3 and 2/5/19. Photo: GNFAC

Multiple large avalanches occurred in the Lionhead area near West Yellowstone after 2-3’ of heavy snow earlier this week. Photo: GNFAC

This avalanche was triggered by snowmobilers on 2/6. 2-3’ of heavy snow earlier this week fell on a weak snowpack making large avalanches possible. Photo: GNFAC

This avalanche was triggered by snowmobilers on 2/6. 2-3’ of heavy snow earlier this week fell on a weak snowpack making large avalanches possible. Photo: GNFAC

From an email, "Observed this large avalanche while driving north from Jackson Hole today.  (on the E, NE aspect of Sawtell Peak, in the Centennial Mountains)"

Likely released in the last day or so with the Avalanche Warnings on Sun, Mon and Tuesday. Photo: B. Fredlund

Snowmobilers in the Lionhead area got unstable test results, easily propagating fractures in ECT tests on a weak layer buried about 50 cm deep. Photo: J. Norlander

This photo was taken by a FS snow ranger on Feb 1st. These avalanches likely occurred towards the end of a period of steady snowfall from Jan 16th to 28th. From e-mail: "The Reas Peak area had 7 slides that I could see from the bottom of the drainage, most of them looked to have occurred with the last storm and had a northerly influence to their aspect. The largest and most recent slide I included in the [above photo], Reas Peak is the highest peak on the left in the photo and the slide path is on a NE aspect. If you look close at the photo you can see a 2-3’ crown on the far left side of the frame on the north aspect of Reas from another slide." Photo: C. Hericks

This photo of an avalanche on the north side of Reas Peak was taken by a FS snow ranger on Friday, Feb 1. It likely occurred towards the end of a period of steady snowfall from January 16th to 28th. Photo: C. Hericks

Mount Jefferson (just north of Reas Peak) is the peak in the background. Nasty avalanche on persistent weak layer in the foreground. Photo: B. VandenBos

Large avalanche on Bald Peak in the Lionhead area near West Yellowstone. Photo: B. VandenBos

A very deep natural avalanche was observed on Sheep Mountain, on January 28th. 

From email: "This was southern facing slope of sheep mountain... Crown was at least 8’... very heavy wind loading."

Photo: H. Menssen

Cracking and collapsing on a 31-degree slope near the Lionshead area down south. The slab was 3-4' deep, and the slope was on the verge of being steep enough to avalanche. From the email: " fractured about 20’x10’ area initially, maybe 3-4’ deep. We got off the hill and it continued to fracture in bigger spots but did not slide more than a foot total." Photo: S. Thompson

Crown of avalanche that was triggered by a group of four skiers. Two were partially buried (1 injured, 1 killed) on 1/25/19. They were all ascending and near the top of the path when the avalanche broke. The top two skiers held onto trees as the avalanche pushed by them. Photo: GNFAC

Overview of avalanche path where a group of four skiers were caught, and two were partially buried (1 injured, 1 killed) on 1/25/19. Crown is marked by black line and location of partial burial/deceased is tip of red arrow. The other partially buried skier was 200' lower. They were all ascending and near the top of the path when the avalanche broke. The top two skiers held onto trees as the avalanche pushed by them. Photo: GNFAC

From an email:

"...was riding with a group near the Two Top area and remotely triggered this slide as rode past this drainage on the top of the ridge. It was a north facing wind loaded slope in the 38 degree slope range. It broke about 12 inches deep and looked like it was from the last snow/wind loading." Photo: J. Norlander

From facebook: "natural avalanche down near reynolds pass. West facing slope, it faces hwy 87 and is named mile Creek trail by usfs. No snowmobiling and haven't ever seen anyone ski it."

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

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

February 2, King and Queen of the Ridge at Bridger Bowl (fundraiser). Register with Bridger to hike in the event, and create a pledge page to raise funds with your Ridge laps.

A snowmobiler triggered a slide in Lionhead on Tuesday, January 8. Photo: D. Mintus

A sledder remote triggered several slides from the bottom of a south facing slope in the Centennial Range, Hell Roaring Creek. Photo: B. Marsh

A sledder remote triggered several slides from the bottom of a south facing slope in the Centennial Range, Hell Roaring Creek. Photo: B. Marsh

Avalanche triggered remotely by a snowmobiler near Lionhead Ridge on January 7, 2019. From email "24 inch crown and about 200 feet wide... on an easterly wind loaded slope"

A snowpit on Lionhead revealed two weak layers. One was under wind blown snow; the other was 1.5 feet above the ground on a thick layer of sugary facets. Photo: GNFAC

From e-mail: "This was a snowmobile triggered slide in a S aspect in the Blue Creek Drainage SE of Reas Peak in the Centennials.  No one was caught and no injuries as far as I can tell".

This was a recent snowmobile triggered avalanche In Tepee Basin, southern Madison range. This slide failed on facets near the ground and ran into a terrain trap. With more snow and wind in the forecast, it will be important to make conservative terrain selections. Photo: GNFAC 

This avalanche in Airplane Bowl off Lionhead Ridge, is south facing at 9,000'. The avalanche was 1-2' deep, 100' vertical and 150' wide (estimated). It likely broke late Sunday or Monday (12/31), during or immediately after the Avalanche Warning. Weak, faceted snow could not support the weekends snowstorm and there were widespread slides. Photo: GNFAC

Collapsing and cracking in Watkins Creek in Lionhead. The snow is weak and collapses like this indicate instability. Photo: B. Rasmussen

Collapsing and cracking in Watkins Creek in Lionhead. The snow is weak and collapses like this indicate instability. Photo: B. Rasmussen

The snowpack at 9,000' above Hebgen Lake near West Yellowstone is 60-70cm (~2 feet) deep. It is mostly weak, sugary facets and will struggle to support the weight of future storms. Photo: GNFAC