20-21

On Mt Ellis (2/27/21) the snowpack has 20-40cm of depth hoar and facets at the bottom. Stability tests took a lot of force to collapse this layer, but it propagated (broke across the whole column) every time once initiated. This is a poor snowpack structure that makes large avalanche possible to trigger if you hit the wrong spot on a slope. Photo: GNFAC

Northern Gallatin, 2021-02-28

From skier obs 2/27/21: "~6-8" of fresh snow. No wind loading or significant signs of instability. Calm winds with scattered clouds and occasional very light snow. Dug a pit at the summit. ... I found plenty depth hoar at the bottom of the snowpack. It was not as weak as what I've seen earlier this season (4F), but we're still talking 4+ mm grains with well formed cups. ECTX and PST 60/120 to end on the depth hoar layer. Pit profile attached."

Northern Gallatin, 2021-02-27

GNFAC Avalanche Forecast for Sat Feb 27, 2021

Snowpack and Avalanche Discussion

<p>The fresh snow is piling up and human triggered avalanches are likely today in the Lionhead area. With more than a foot of new snow over the last two days, avalanches can break either under the new snow, or step down to weak layers at the bottom of the snowpack. Avalanches in the new snow will be most easily triggered and the largest on slopes where it has been drifted into deeper cohesive slabs. The weak layers at the ground are unlikely to give you any warning before you trigger an avalanche. Give them time to accommodate this load of new snow. Avoid riding on or underneath all steep slopes. The avalanche danger is rated CONSIDERABLE.</p>

<p>With a little less new snow, avalanches aren’t quite as likely across the rest of the advisory area, but triggering one is possible and they could break very deeply. Strong winds over the last few days created wind drifts that will be harder to identify with a dusting of new snow on top. Winds dropped off last night, so on many slopes the most recent snow won’t be drifted but particularly watch out if you find one where it was. These drifts can avalanche under the weight of a skier or rider. Yesterday, riders on Buck Ridge saw a recent avalanche that broke naturally on a wind-loaded slope (<a href="https://www.mtavalanche.com/images/21/natural-avalanche-buck-ridge-0"><…;).</p>

<p>The more serious issue is that we have the recipe for deep slab avalanches. Deep slabs are tricky. It’s hard (maybe impossible) to figure out which particular slope is going to break, but if a slope goes, the resulting slide will be huge and deadly (<a href="https://youtu.be/Ychm42ihtjk"><strong><u>Blackmore video</u></strong></a>, <a href="https://youtu.be/65JO-4w4qXo"><strong><u>McAtee Basin video</u></strong></a>). We don’t trust the snowpack and neither should you. Continuing to avoid all steep slopes is the best solution.</p>

<p>With large human triggered avalanche possible, the avalanche danger is rated MODERATE.</p>

<p>&nbsp;</p>

<p>Avalanches beneath recently wind-drifted snow remain the primary concern near Cooke City, but avalanches breaking deeper are also possible. Earlier this week, an avalanche broke deeply on weak layers near the ground on a wind-loaded slope in Hayden Creek (<a href="https://www.mtavalanche.com/node/24432"><strong><u>details</u></strong>…;). This slope had avalanched several times already this year keeping the snowpack unusually thin and weak. While these conditions aren’t widespread, stay on alert in case you encounter one of these thin areas with weaker snow. The avalanche danger is rated MODERATE today.&nbsp;</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

The Beacon Park at Beall Park in Bozeman is running!

The Friends of the Avalanche Center in partnership with the City of Bozeman put in a Beacon Park at Beall Park. It is located on the north side of the Beall building between N. Bozeman Ave. and the ice rink.

Natural avalanche on Buck Ridge

Buck Ridge
Northern Madison
Code
SS-N-R3-D2
Latitude
45.17190
Longitude
-111.38000
Notes

Natural avalanche on Buck Ridge. Observed 2/26/2021. Looks to have failed recently. Propagated widely.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
3
D size
2
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year