19-20

Observed a sizable deep slab in the Divide basin which appeared to have run within the last few days. The crown extended from the southern end of the basin (northeast facing) through the summit run off Divide (southeast facing)--maybe around a mile. Slab height varied, with the upper end pushing 10 feet and the lower closer to a foot or two. On Divide, the crown approached the summit and debris had run across the flat to the mature trees. Looked like it may have been cornice triggered at the southern end on thinner cover in rocky terrain.

Northern Gallatin, 2020-02-16

We encountered a natural avalanche that appears to have been triggered by a cornice drop. There seemed to be very little fresh snow on the slide surface so we suspect it occurred recently (Feb 14?). The slide occurred on the west side (east facing side) of Bear Basin (pinpoint on the map below). The avalanche was probably 200 feet wide at the top so it clearly propagate across the slope. Crown was 2 to 5 feet tall. We did not hike in there to investigate more carefully. There is a fair amount of trees on this part of the ridge.

Northern Madison, 2020-02-16

Skied the NE shoulder of Divide Peak. Spotted a 1/4 to 1/2 mile long crown spotted along the NE face of Peak 10,024, between Divide Peak and Hyalite Peak. We could not directly determine the crown height, but it was highly visible from our location ~1 mile away. Photo: Tom Kalakay

Northern Gallatin, 2020-02-16

Cornice fall triggered soft slab slab in Spanish Peaks

Yellow Mountain
Northern Madison
Code
SS-NC-R3-D2
Elevation
9300
Aspect
S
Latitude
45.29950
Longitude
-111.32000
Notes

Cornice fall triggered a soft slab avalanche in the Spanish Peaks on the afternoon of 2/13/2020.

From email: "100 feet wide, slid the new snow layer maybe 2-3 feet deep, made a pretty good runnel, and went close to full path , so it must have entrained a decent amount of snow to travel that far .."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Cornice fall
R size
3
D size
2
Problem Type
New Snow
Vertical Fall
2000ft
Slab Width
100.00ft
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Cornice fall triggered a soft slab avalanche in the Spanish Peaks on the afternoon of 2/13/2020.

From email: "100 feet wide, slid the new snow layer maybe 2-3 feet deep, made a pretty good runnel, and went close to full path , so it must have entrained a decent amount of snow to travel that far .."

Photo: R. Hollow

Northern Madison, 2020-02-15

GNFAC Avalanche Forecast for Sat Feb 15, 2020

Snowpack and Avalanche Discussion

<p>Gusty west winds are drifting yesterday’s new snow into cohesive slabs that will be easily triggered today. Mostly these slabs are relatively thin, but there are also be deeper pockets where you could trigger a larger slide in the new snow. Watch out for deeper drifts near ridgelines. Identify and avoid the most heavily windloaded slopes. Feel for the snow stiffening under your feet and look for cracks shooting out in front of your skis/sled as signs you’ve found one of these potentially dangerous drifts.</p>

<p>Deep in the snowpack there are weak layers at the ground that can’t be forgotten. Yesterday’s little bit of new snow wasn’t a huge load on these layers, but it is enough to keep them from entirely going to bed. Windloaded slopes got a larger load and if you trigger a slide in the new snow, it could step down to the layers near the ground. Are you likely to trigger a deep slab avalanche today? No. But the possibility is out there, and if you do, bad outcomes are likely. It’s only be few days since the last slide on these layers (<strong><a href="https://www.mtavalanche.com/images/20/remotely-triggered-slide-garnet">…;). Watch a few of the videos we’ve made standing beneath huge crowns over the last couple weeks to remind yourself of the size and power of these slides (<strong><a href="https://www.youtube.com/watch?v=tJUrhcTRHac&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=7vDe6LE-nhU&amp;list=PLXu5151nmAvSbcbVf…;, <strong><a href="https://www.youtube.com/watch?v=VXVEIqSWvdY&amp;list=PLXu5151nmAvSbcbVf…;

<p>The avalanche danger is MODERATE today across our forecast area.</p>

<p>If you get out, please send us your observations no matter how brief. You can fill out an&nbsp;<strong><a href="https://mtavalanche.us17.list-manage.com/track/click?u=6653a830e4819c9e…; target="_blank">observation form</a></strong>, email us (<strong><a href="mailto:mtavalanche@gmail.com&quot; target="_blank">mtavalanche@gmail.com</a></strong>), leave a VM at 406-587-6984, or Instagram (#gnfacobs).</p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out and plan to attend one or two: Events and Education Calendar.

COOKE CITY

Every Friday and Saturday, Snowpack Update and Rescue Training. Friday, 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.

BOZEMAN