Northern Gallatin

Snow on a post along the Blackmore trail shows how much snow has been falling. I suspect the slow and steady nature of snowfall is what allowed it to do this.

Storm slab avalanche that broke about 400 ft wide at 9200 ft in a ENE facing sub-cirque of Blackmore

Two storm slab avalanches on the east face of Blackmore 8-10 inches deep. One of them ran down the normal skin track.

image of snowpit from Mt Blackmore, NE facing, 9185', HS almost 5 ft

Snowpit profile from Mt Blackmore, NE facing, 9185', HS almost 5 ft

Avalanche Activity

We spotted 6-7 storm slabs that failed about 8-10 inches deep. There were 3 on the East face Blackmore, 1 on the north face, 1 on north facing flank, and 1 notable one in a steep below treeline cirque ENE facing (this one broke ~400 ft wide). A possible 7th was down the Fox creek drainage. It seemed a bit random where they happened and didn't. They likely occurred sometime late yesterday afternoon during snowfall and high winds. This instability should be mostly stabilized by tomorrow.

We didn't see any avalanches that broke deeper in the snowpack

Other signs of instability 

no collapsing or cracking

Skiing/riding quality 

5 star deep powder and hard trailbreaking, aka trenchtown

Snowpack

We had limited time and only dug one snowpit (attached profile image). We'd like to go back and poke around in some shallow rocky areas. Pit attached. General impression is that it is very deep, and mostly strong. The Shower Falls SNOTEL is at 124% of median swe.

Early December facets have gained a lot of strength, and stability is moving in the right direction. With so much new snow (and more coming Friday/Saturday), I worry about finding a trigger point in a thinner area and then causing an avalanche to break widely into deeper areas. After the Fri/Sat storm if no more snow or wind come for a little bit of time, stability should improve very quickly

Note

The photo of snow on the sign post really shows how snowfall has been steady, slow, and non-stop. My hunch is that initially snow piled up on top of the post. Then it began to sag (or creep) to one side but slowly enough to not break. With each storm a little more snow was added and the pile of snow crept more to the side. Cool.

Went climbing in the greater G1 area yesterday. Pockety slide paths and gullies near G2- Hangover were starting to cross load. Slab formation was just beginning (surface cracking and notable propagation.) Slabs did not have the volume to be consequential, yet. There is a lot of AST (thigh deep trail breaking places). These lower elevation paths are often relatively benign since they are generally well protected. A little bit more wind and slab formation could create hazardous travel in this areas with unforgiving runouts. 

Debris piles from recent DL and likely SS avalanches were observed under cliff bands and gully features in the area that have likely run naturally throughout this storm cycle.

No signs on instability on Mt. Ellis.  Skinned to the top and descended in the trees to the north of the burn.  Ellis does not seem to have the troubling snow structure found in much of the advisory area.