Cooke City

Today, we toured south of Cooke City, up Republic Creek and Republic Mountain. We spotted widespread, weakening snow surfaces: surface hoar feathers at lower elevations, faceted snow on cold, shady slopes up high, and faceted snow beneath crusts on solar aspects. Our pit on an E aspect at 9460' did not produce unstable test results, but showed the top 1.5' of snow to have faceted and weakened during this bout of high pressure. These layers are not concerning now, but will certainly be top of mind when the next storm system arrives over the weekend. 

We spotted several loose wet avalanches that occurred yesterday in steep, rocky terrain up Sheep Creek. We also noted an old, deep persistent slab avalanche on a NW' aspect near the south end of the Republic Creek drainage. This likely broke around a week ago. 

Skies were clear, winds were calm, and temperatures were warm in the sun and chilly everywhere else. 

On Jan 27 we saw  a cornice fall on a very big steep slope up Republic Creek which did not trigger anything large or deeper, but entrained some snow and ran over a thousand feet vertical. Photo: GNFAC

On Jan 27 We saw one old, but very large persistent slab avalanche further up Republic Creek (pictured). It was on similar aspect and elevation as a somewhat more recent persistent slab in nearby Hayden Creek, North-northeast, 10,000'. It appeared to be 6'+ deep and 500'+ wide. The bed surface and crown had been partially drifted in, so it seemed it was probably at least a week old...? Photo: GNFAC

We skied up west Woody Ridge and skied down into Hayden Creek about 500 feet, then back up and over, and out Republic Creek.

Skies were clear with calm winds and a light breeze at the ridgetop. Temperatures were still mostly cold, single digits down low and teens up high in the morning. The sun felt hot mid-day, snow bombs were falling off trees and there were some small rollerballs around steep rocks on southerly facing slopes.

We saw one old, but very large persistent slab avalanche further up Republic Creek (pictured). It was on similar aspect and elevation as a somewhat more recent persistent slab in nearby Hayden Creek, North-northeast, 10,000'. It appeared to be 6'+ deep and 500'+ wide. The bed surface and crown had been partially drifted in, so it seemed it was probably at least a week old...?

There was also a recent cornice fall on a very big steep slope up Republic Creek (picture) which did not trigger anything large or deeper, but entrained some snow and ran over a thousand feet vertical.

We dug a pit at 9,900' on a west aspect. Snow depth was 150cm (5 feet). We had an ECTN11 below 3 inches of snow on top of small sugary facets near the surface. There were soft (4f+) sugary facets at the bottom of the snowpack, but they did not break in an ECT or with extra force. Snow depth above 9,000' was ~4 feet average based on a few places we probed as we toured up.

There were signs of a lot of previous wind up high. It has been a few days without wind, but there are probably some isolated instabilities of small stiff wind slabs sitting on facets which could be triggered.