Caution advised for snow falling off of building roofs. Park accordingly.

Dangerous avalanche conditions may already exist in many back country areas, please call the Recorded Avalanche Advisory 406-587-6981 for the most current conditions.

Today: Snow likely. Snow accumulation of 1 to 2 inches. Chance of snow 70 percent. Highs 16°F to 22°F.

Tonight: Snow likely in the evening...then snow after midnight. Snow accumulation of 2 to 3 inches. Chance of snow 90 percent. Lows 5°F to 11°F.

Thursday: Snow likely. Snow accumulation of 1 to 2 inches. Total snow accumulation 4 to 7 inches. Chance of snow 70 percent. Highs 16°F to 22°F.

Thursday Night: Cloudy. Chance of snow in the evening...then slight chance of snow after midnight. Chance of snow 40 percent. Lows 0°F to 6°F.

Friday: Mostly cloudy with a 20 percent chance of snow. Highs 14°F to 20°F.

Friday Night: Partly cloudy. Lows -2°F to 4°F.

Saturday: Partly cloudy. Highs 16°F to 22°F.

Saturday Night: Partly cloudy with a 20 percent chance of snow. Lows 1°F to 7°F.

Sunday: Partly cloudy with a 30 percent chance of snow. Highs 16°F to 22°F.

Sunday Night: Partly cloudy with a 20 percent chance of snow. Lows 0°F to 6°F.

Monday: Partly cloudy with a 20 percent chance of snow. Highs 17°F to 23°F.

Monday Night / New Years Eve: Partly cloudy. Lows 3°F to 9°F * Happy New Year *

Tuesday / New Years Day: Partly cloudy. Highs 19°F to 25°F. * Happy New Year *

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Mountain Weather

At 6:00 a.m. it just started snowing around Big Sky with an inch falling. Mountain temperatures are 5° to 10° Fahrenheit with southwest winds at 15 to 25 mph. The Bridger Range is calmer and warmer with 5 to 10 mph winds and temperatures in the teens Fahrenheit. Today will be cloudy as temperatures rise into the upper teens Fahrenheit with light to moderate southwest winds. Tonight winds will switch to the northwest, but speeds will not increase much. Scattered snow showers will drop 1 to 3 inches by morning.

Snowpack and Avalanche Discussion:

The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone and Cooke City:

Light winds have stopped fueling wind-drifts. Yesterday, ski patrols could trigger soft wind slabs with ski cuts, but they were not propagating far. I expect these drifts to be more stubborn today.

A lot of slopes in the backcountry have a stable snowpack (photo). Even with faceted grains near the ground, these slopes are not propagating fractures in stability tests. This fact alone is not enough to point to stability, but when these tests are performed multiple times on the same slopes over the course of weeks, coupled with loads of new snow followed by minimal avalanche activity, we begin to feel confident in our assessment.

Although many slopes are stable, some are not. The difference between the two is not obvious; however there are two things to look for. The first is that slopes thinner than three feet deep seem to be the weakest. Second, clean fractures in our stability tests signal unstable conditions (photo, video). Finding just one unstable result is enough evidence to wave the white flag of surrender and stick to slopes less than 30 degrees.

Eric skied Mount Ellis in the northern Gallatin Range on Saturday and found two feet of weak, faceted snow, but without the overburden of a slab, its structure was not unstable. The variability of conditions are on full display in the Bridger Range where the Football Field of Saddle Peak and Truman Gulch had stable test results, but further north near Frazier Basin they were unstable (snow pit). This variability requires careful evaluation and is the reason today's Avalanche Danger is rated MODERATE on all slopes throughout our advisory area.

Last week's period of cold, sometimes clear weather, turned the top few inches of snow into weaker, small grained facets. These did not form everywhere, and to further complicate their distribution, strong winds on Friday scoured them from some slopes too. This layer is now capped by the recent snows. It is not deep enough to be a grave avalanche concern yet, but we'll be looking for it since these layers tend to persist.

The next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations, drop us a line at mtavalanche@gmail.com or call us at: 406-587-6984.

PHOTOS, SNOWPITS, and VIDEOS

1. For links to all photos and videos listed in the above report, please visit this Link.

2. We've recently uploaded more photos and snowpits to our web site, more than what are linked in the advisory.

3. We're creating a series of "How To…" stability test videos. So far we've got clips on performing a CT and ECT. There are located under Stability Tests on the Resources page.

Information provided by Doug Chabot, Mark Staples, and Eric Knoff from the Gallatin National Forest Avalanche Center. For Photos and Videos, please visit the Avalanche Centers Website!

If you have any snowpack or avalanche observations, drop them a line at mtavalanche@gmail.com or call: 406-587-6984.

For detailed Avalanche Terms utilized here, please see the Avalanche Glossary.