Skiers triggered 2 large slides Flanders Mtn.

Flanders Creek
Northern Gallatin

From Obs: "... Our party of two was ascending southwest on a rib with the intention of reaching the ridgeline. At 9800', the upper member of our party triggered a D2.5 with an approximately 100' crown immediately to our south. Crown height appeared 2-3' and the slide traveled approximately a distance of 2,000' and 500 vertical feet down mountain. Within a few seconds, we remote triggered to the north a D3 with an approximately 200' crown. Crown height appeared up to 7' at highest point and slide traveled approximately 300 vertical feet down mountain. The remote triggered slide started approximately 15-20 feet to the north of the location of the lower member of our party, who was approximately 30 vertical feet below the upper member of our party. After the slide the upper member of our party noticed a shooting crack at his elevation. Two skiers and one dog were ascending below us. They observed the avalanche and later mentioned that they were approximately 150 feet in distance from the toe of the remote triggered slide, which completely covered their skintrack. Nobody caught or buried."

From group that was below: "Finished a snow pit at 45.434589, -110.940957. Results were ECT-X, Aspect: 110 deg, Angle: 27 degrees, Depth: 90 cm, Weak layer was above melt/freeze at 60 cm, fist hardness above 62 - 67 cm. Then fairly cohesive newer snow 70 - 90 cm. Weak layer did not budge, even when levered with the shovel.

Knowing there was one party of two ahead of us, we continued to 45.434716, -110.94124 when they triggered slide above. It ran through one of the avalanche paths behind us, that we had crossed. We whooped to see if someone was the trigger and if they were ok, they yelled back all was ok. Our mistake was assuming the party ahead was taking, what we consider to be, the standard route up Flanders, not the subtle ridge that we figured was loaded by the month of west/sw winds We were wrong and were traveling below them but still were traveling in the older trees and not in slide paths, yet another example of why you follow protocol. Anyways I took a bunch of pics. Pin on map is about where they triggered it."

Number of slides
Number caught
Number buried
Avalanche Type
Hard slab avalanche
Trigger Modifier
u-An unintentional release
R size
D size
Bed Surface
O - Old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
36.0 inches
Vertical Fall
Slab Width
Slab Thickness units
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year