Regional Conditions for Lionhead Range

From obs 4/9/21: "...we saw widespread natural wind slabs on N-NE eastern slopes in the Northern Absarokas (photo). Winds increased throughout the morning, and evidence of wind transport became more apparent at higher elevations. We found that on aspects unaffected by wind loading, the new snow layer was not cohesive and only saw minor sluffing." Photo: E. Schreier

Skiers had a collapse which made this crack on a south facing slope with a shallower, wet snowpack around 9,000' near Cooke City. Photo: J. Redfield

This wet slab was reported on 4/4/21 around 8,200' elevation in the Main Boulder drainage south of Big Timber, outside of our advisory area. It happened that day or very recently during extended above freezing temperatures. Photo: G. Smith

Extreme winds on 3/28/21 transported snow that fell over the past week into fresh wind slabs. Photo: BSSP

From obs 3/28/21: "Saw this slope which frequently slides had been triggered on our way out last night [lower left in photo]. Slid to the ground but I expect it was mostly new snow as there is a larger old crown visible further uphill... I did see two other small pocket slides yesterday also in new snow on bed surfaces of older slides... General snowpack is getting very deep now but a thick junk layer remains at the ground everywhere I dug sleds out." Photo: J. Gerardi

From obs: "Deep slab avalanche in Blackmore Basin that appeared to break on the depth hoar near the bottom of the snowpack. It was on a wind loaded NE facing slope at approx. 9,500 and looked to break on a slope in the 35-40 degree range. The crown was about 8'-10' deep and 200' wide. It broke to the ground and ripped out several small trees." Photo: JR Mooney

Ian and Dave stop to do a quick stability test as they hunt for a layer of weak snow 1-2 feet under the surface. Photo: GNFAC

From obs: "On our way up the summer trail route to Hyalite Peak our party of three remotely triggered a small avalanche from the skin track at around 9,600ft on a east facing aspect. The storm slab went about 4 inches deep and 150-200ft across a small roll over feature. We were about 150ft away when we triggered the slide." Photo: C. Kussmaul

The snowpack in the Centennials is remarkably similar to the Lionhead area outside West Yellowstone: 6 feet of snow at 9,200 feet. The stability will get worse with snow this weekend (19-21 March) because the surface snow is week and the new snow will not bond to it (near-surface facets). Photo: GNFAC

Cornices along Lionhead Ridge. 3/16/2021

Photo: GNFAC

Seen from near Ennis on 3/4/21. On Finger Mountain in the southern Madison Range. Photo: D. Frohman

We saw these recent wet loose avalanches on 3/6/21. SW aspect, 9,100'. They likely ran during above freezing temperatures between 3/3 and 3/5. Photo: GNFAC

From obs: "Small D1 avalanche on south-eastern aspect around 7800ft. Looks like solar released on older layer a day or two ago."

Photo: M. Mailly

From obs: "While touring above the canyon this morning, I noticed a very recent wet slide (would guess this incident occurred yesterday afternoon, March 4th). This was a skier triggered slide on a E aspect at an elevation of 7200. This slide was roughly 50 feet wide and ran about 50 feet, I estimated this crown to be 2-3 feet deep, slid all the way to the ground. This occurred below a steep roller."

Photo: T. Saulnier

Wet loose avalanches released in the warm sunshine on Tuesday, March 2nd. We expect many more in the coming days. Photo: S. Jonas

Sled Skiing in Third Yellow mule... after an air onto the slope the impact from landing resulted in a fracture and failure to / near the ground... in addition, a remote trigger occurred on adjacent slope... 200-300 ft to the skiers right. No body was caught in either slide. Skier that initiated failure was moving at high speed and was beyond slide path before majority of snow movement began. Photo: W. Miller

Sled Skiing in Third Yellow mule... after an air onto the slope the impact from landing resulted in a fracture and failure to / near the ground... in addition, a remote trigger occurred on adjacent slope... 200-300 ft to the skiers right. No body was caught in either slide. Skier that initiated failure was moving at high speed and was beyond slide path before majority of snow movement began. Photo: W. Miller

Sled Skiing in Third Yellow mule... after an air onto the slope the impact from landing resulted in a fracture and failure to / near the ground... in addition, a remote trigger occurred on adjacent slope... 200-300 ft to the skiers right. No body was caught in either slide. Photo: W. Miller

This avalanche was triggered on Sunday, 2/28, when a skier released another slide 2-300 feet away. It broke at the same time. No one was caught. This was in the Third Yellow Mule on Buck Ridge.  Photo: W. Miller

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

Riders triggered this slide on 2/28/21 near Red Canyon/Cabin Creek, north of West Yellowstone. Nobody caught or injured, but close call.

There was 6' of snow off the ridge in the Bridger Range on an east facing slope. The top 2 feet were recent wind drifting that broke clean in our stability test which indicated unstable conditions (ECTP18). We expect similar conditions and instability with wind-loaded slops throughout our forecast area. Photo: GNFAC

In the last 24 hours (2/28) 12" of low density powder and 40-50 mph west wind made it easy to trigger wind-drifted snow. Alex kicked these drifts which cracked and moved. We expect similar conditions and instability with wind-loaded slops throughout our forecast area. Photo: GNFAC

This natural avalanche occurred on a slope that was wind drifted with cross-slope winds. It was a NE facing slope at 9,000 feet and likely ran over the weekend (2/20). Photo: GNFAC

This natural avalanche was likely triggered by a falling cornince in the last day or two. The slope is in the Wilderness and was seen from the boundary. Wind drifted snow is a concern in this area. Photo: GNFAC

On 2/13/21 riders reported they triggered this avalanche, and remotely triggered two other slides. Nobody was injured. One partially buried.

On 2/13/21 riders reported they triggered this avalanche, and remotely triggered two other slides. Nobody was injured. One partially buried.

Snowmobile triggered slide on Lionhead Ridge in Upper Watkins drainage on 2/11/2021.

Natural avalanche on Lionhead Ridge in upper Watkins Creek. Likely broke on Sunday 2/7.

Photo: GNFAC (2/10/2021)

Sledders triggered this slide on 2/6/21 in West Targhee Creek near Lionhead. No one was caught.

A snowmobiler triggered this avalanche on Monday (2/1/2021) at Lionhead. No one was caught. Photo: Anonymous

A snowmobiler triggered this avalanche on Monday (2/1/2021) at Lionhead. No one was caught. Photo: Anonymous

This small avalanche was below the corner of Lionhead peak. It was one of the smaller slides during the avalanche cycle that occurred 1/29 and 1/30. Photo: GNFAC

The avalanche broke in the new snow, but stepped down into deeper layers (sugary facets) mid-path. This can occur when there are multiple weak layers in the snowpack. Photo: GNFAC

Every path along the shoulder of Targhee Peak (Lionhead area) avalanched naturally during the storm 1/29 and 1/30. Photo: GNFAC

This steep north facing slope avalanched about 3 weeks ago on depth hoar when a snowmobiler triggered it. It got reloaded with new snow and wind drifts and avalanched a second time! Photo: GNFAC

This natural avalanche occured on a NE facing slope at 8600". It was 2' deep, 500' wide and 250' vertical. The avalanche broke on a thin layer of facets during the storm. SS-N-R3-D2-O. Photo: GNFAC

On the north end of Lionhead Ridge is Airplane Bowl. The crown line extends across the entire bowl on the right with a separate avalanche on the left. Photo: GNFAC