Two layers of surface hoar (up to 2 cm flakes) are in the upper few inches of the snowpack around Lionhead. The rest of the snowpack is fist to 4-finger hardness faceted grains which are not strong. The avalanche danger will rise with more snow on these layers. Photo: GNFAC
11-12
GNFAC Avalanche Forecast for Thu Dec 22, 2011
Snowpack and Avalanche Discussion
The Madison and Gallatin Ranges, and the Lionhead area near West Yellowstone:
Sometimes avalanche forecasting is easy and today is one of those times. Yesterday’s snow combined with a weak snowpack will produce avalanches. Total snowfall for the storm was:
GNFAC Avalanche Forecast for Wed Dec 21, 2011
Snowpack and Avalanche Discussion
The Bridger, Madison and Gallatin Ranges, the Lionhead area near West Yellowstone, and the mountains around Cooke City:
If the storm continues as predicted, the avalanche danger will rise. We have a weak snowpack and the new snow will likely be the first real test of its integrity.
A small human triggered slab avalanche in Sheep Creek outside Cooke City. Approximately 4-10" deep and about 60' wide; NE facing slope around 9400'.
GNFAC Avalanche Advisory for Tue Dec 20, 2011
Snowpack and Avalanche Discussion
The Bridger and Madison Ranges, the southern Gallatin Range and the Lionhead area near West Yellowstone:
GNFAC Avalanche Advisory for Mon Dec 19, 2011
Snowpack and Avalanche Discussion
The Bridger and Madison Ranges, the southern Gallatin Range and the Lionhead area near West Yellowstone:
Avalanche forecasters commonly track well developed weak layers such as surface hoar, depth hoar and near surface facets. By mapping the distribution of a weak layer, many times it becomes possible to determine what areas may be unstable. This year is different.