24-25

Wind slab in the bridgers

Date

Sun, 02/09/2025 - 13:50

Activity

Skiing

Toured the ramp today and observed an avalanche in hour glass. It was a soft slab that broke in some rocks near the top of the chute, it ran the entire length of the chute and the debris was fairly large (d1.5). The crown looked to be between 8” and 1.5 ft, and was about 30 ft wide.

Region

Bridger Range

Observer Name

Jay Alford

Natural and human-triggered wind slabs, Cooke - 9 Feb 2025

Read more about Natural and human-triggered wind slabs, Cooke - 9 Feb 2025

Test Scores Bacon rind

Date

Sun, 02/09/2025 - 12:00

Activity

Skiing

Bacon Rind

Consistent crusts at Around 75cm up and 63cm up

Facets at 35cm up to Ground

44.96280, -111.08678, 10:14

7850ft

68 E

20 degrees

HST 110cm

ECTP 25 65 cm up

ECTp 16 35 cm up

44.96019, -111.09583, 11:30

8578ft

59 NE

10 degrees

Hst110cm

ECTN25 75cm up

ECTP16 63cm up

Region

Southern Madison

Location (from list)

Bacon Rind

Observer Name

Tagg Cole

Snow Pit near Mt. Blackmore

Date

Sun, 02/09/2025 - 12:05

Activity

Skiing

Dig on the way up to Mt. Blackmore on a W aspect at 8000’. Snow was pretty shallow (130cm) for the area. Noticed the dust layer underneath the most recent snow. Had unremarkable pit results. ECTN11 on the dust layer being the most notable. Saw a couple of small wind slabs and intentionally triggered one on a small rollover. Definitely a good bit of active transport going on out there.

Region

Northern Gallatin

Location (from list)

Mt Blackmore

Observer Name

Eric Heiman

Wind slab avalanches near Cooke

Date

Sun, 02/09/2025 - 11:40

Activity

Snowmobiling

We rode over Daisy Pass out to Mt. Abundance, then behind Fisher and around Scotch Bonnet back to Lulu Road. Snowed light this morning with partly sunny skies mid-day. Wind was moderate and gusty out of the west. We were able to see most terrain north of the passes. Clouds obstructed great views of east Henderson and east Miller.

We saw a fresh natural wind slab near Wolverine, R1-D1.5 (photo attached). We watched two snowboarders trigger separate wind slabs, while riding one at a time in avalanche terrain, on the south side of Scotch Bonnet (photos attached). They rode away safely. These looked 12" deep and 20' wide, and entrained snow to run a good distance, R1-D2.

We dug a pit on the south shoulder of Mt. Abundance and had an ECTX. There were some density changes in the recent snow that might contribute to wind slabs or storm slabs breaking easier for another day or two, but they seemed more stubborn than yesterday.

Wind slab avalanches were the primary concern today, and I expect they will continue to grow tonight and with any more wind tomorrow. They will remain likely and easy to trigger for at least another day.

We have not seen any persistent slab avalanches breaking below last week's snow or deeper over the last few days. This is a good sign, but I am not ready to write off the possibility quite yet. It is worth continuing to dig and test for buried weak layers for now. The avalanche on east Henderson last Tuesday and the avalanche on Crown Butte last Monday were deep and possibly broke on persistent weak layers, and were on heavily wind loaded slopes. These types of areas are worth avoiding and where a bigger avalanche may be possible to trigger.

Region

Cooke City

Location (from list)

Scotch Bonnet

Observer Name

Alex Marienthal

preserved SH on Ellis

Date

Sat, 02/08/2025 - 13:50

Activity

Skiing

Location: N shoulder Ellis, in open treed area well off ridge and protected from prev. wind effect. El about 8000', Asp NE. Slope 15 deg.

HS 150cm. Found preserved SH 5-8 mm at 98 cm. 1F slab above the SH, 1F+ below. CTM17 and 12, SP, on this layer dn 52 cm. ECTP21. 4 out of 5 lemons.

Folks are skiing the going home chutes and the burn in that zone without? incident.

Could be the classic MT Ellis setup where it never quite snows/blows enough to get action.

Region

Northern Gallatin

Location (from list)

Mt Ellis

GNFAC Avalanche Forecast for Sun Feb 9, 2025

Snowpack and Avalanche Discussion

Human-triggered avalanches are likely, especially where snow that fell over the last week is drifted into thicker slabs. Avalanches could break within the recent snow or on persistent weak layers buried 1-3 feet deep below the last week’s snow.

Wind slab avalanches will be easy to trigger where recent snow has been drifted by west and south winds into thicker slabs.

Persistent slab avalanches are a primary concern as they could break hundreds of feet wide and 1-3 feet deep, or deeper on wind-loaded slopes. Weak, sugary layers of facets and surface hoar are buried 1-3 feet deep below the last week’s snow. These weak layers appear to be most widespread near West Yellowstone and the southern Madison and Gallatin ranges, but have been found elsewhere (<a href="https://www.mtavalanche.com/node/34043"><span…. Ellis observation</a>). You should keep them in mind and be on the lookout no matter where you travel in the forecast area. Yesterday we rode north of Cooke City and did not see clear evidence that these weak layers are a widespread concern, but the snowpack needs more time to adjust to all the recent snow before we have confidence to rule out the potential for larger slides (<a href="https://www.mtavalanche.com/node/34067"><span…;).

Storm slab avalanches can break on density changes within the recent snow. These instabilities should stabilize within a couple days, but the cold temperatures could slow that process. We have had reports of avalanches breaking within the new snow throughout the week (<a href="https://www.mtavalanche.com/images/25/small-avalanche-near-round-lake">… from Cooke City yesterday</a>, <a href="https://www.mtavalanche.com/node/34058"><span… observation</a>, <a href="https://www.mtavalanche.com/node/34051"><span… observation</a>). Yesterday near Cooke City we found lower density layers of recent snow preserved below harder slabs. Be aware that avalanches could break within the recent snow even where it is not drifted (<a href="https://youtu.be/Jvuidj51Djw">…;).

At lower elevations around the valleys snow depths are notably deep, particularly on some steep slopes that don’t often hold much snow. Yesterday Dave noted this abundance of snow in Sourdough canyon, and he wrote a great <a href="https://www.mtavalanche.com/node/34062"><… with avalanche concerns and travel advice to keep in mind for these areas that don’t typically have as much snow and avalanche potential</a>.

Cautious route-finding and careful snowpack evaluation are essential today. Either avoid slopes steeper than 30 degrees or evaluate the snowpack for recent drifting and buried weak layers before getting onto those steeper slopes. Watch for cracking across the snow surface as a sign the recent snow or wind drifts could avalanche on steeper slopes. Dig down a few feet to assess for buried weak layers. Choose smaller slopes to minimize the size of potential avalanches, and slopes without hazards like trees or cliffs that make any size slide more dangerous.

The avalanche danger is CONSIDERABLE.