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 / Christmas Day: Breezy. Mostly cloudy then becoming partly cloudy late in the morning then becoming mostly cloudy. Southwest winds 15 to 20 mph. Highs 13°F to 19°F. Lowest wind chill readings -10°F to -20°F in the morning. * Merry Christmas *

Tonight / Christmas Night: Windy. Partly cloudy in the evening...then mostly cloudy with a 20 percent chance of snow after midnight. Southwest winds 25 to 35 mph with gusts to around 50 mph becoming south around 15 mph early in the morning. Lows -2°F to 4°F. Wind chill readings -13°F to -23°F. * Merry Christmas *

Wednesday: Cloudy. Chance of snow in the morning...then snow likely in the afternoon. Snow accumulation around 1 inch. Chance of snow 70 percent. Highs 19°F to 25°F.

Wednesday Night: Snow likely. Snow accumulation of 1 to 2 inches. Chance of snow 70 percent. Lows 6°F to 12°F.

Thursday: Snow likely in the morning...then chance of snow in the afternoon. Snow accumulation of 1 to 2 inches. Total snow accumulation 3 to 5 inches. Chance of snow 60 percent. Highs 17°F to 23°F.

Thursday Night: Mostly cloudy with chance of snow in the evening... Then partly cloudy with slight chance of snow after midnight. Chance of snow 30 percent. Lows 4°F to 10°F.

Friday: Partly cloudy with a 20 percent chance of snow. Highs 15°F to 21°F.

Friday Night: Partly cloudy. Lows -1°F to 5°F.

Saturday: Partly cloudy. Highs 17°F to 23°F.

Saturday Night: Partly cloudy with a 20 percent chance of snow. Lows 2°F to 8°F.

Sunday: Partly cloudy. Highs 18°F to 24°F.

Sunday Night: Partly cloudy. Lows 1°F to 9°F.

Monday: Partly cloudy. Highs 19°F to 25°F.

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Mountain Weather

This morning is when we all found out if we've been naughty or nice, as if we didn't already know. Santa is a judgmental soul but still brought most of us gifts of snowfall: 5 to 6 inches in the northern Gallatin and Madison Ranges, 3 to 4 inches in the southern mountains and just a trace, the equivalent of a lump of coal, to the Bridger Range. Winds spiked yesterday afternoon to 30 mph for a couple hours, but otherwise have been light at 10 to 15 mph out of the west. Mountain temperatures are in the single digits Fahrenheit and will only rise into the teens Fahrenheit today under clearing skies. No new snow is expected in the next 24 hours.

Snowpack and Avalanche Discussion:

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

Yesterday afternoon's snowfall was light, 5% density, powder. Ski Patrols on Lone Peak reported the new snow getting blown into thin wind slabs that easily zippered with ski cuts. On some slopes this new snow capped a thin layer of small-grained facets that formed at the surface during the previous days of dry weather. This weak layer will keep wind slabs touchy. Skiers reported similar weakness north of Big Sky in Beehive and Middle Basins and also near Cooke City where parties reported fractures propagating thirty feet out from their skis.

The snowpack is generally strong (Eric's photo), but there are still a few slopes with weaker, faceted snow near the ground. These slopes tend to be less than three feet deep. Eric skied Mount Ellis in the northern Gallatin Range on Saturday and found two feet of weak, faceted snow. Mark rode in the Lionhead area on Saturday and saw avalanches from seven days ago that released on facets near the ground. A skier on Saturday in Middle Basin also found poor snowpack structure on a few slopes.

Wind loads near the ridgelines and above tree line is a problem today, especially because these drifts are sitting on facets and prone to avalanche. Consequently, these slopes will have a CONSIDERABLE Avalanche Danger. Most slopes without a wind-load are generally stable; however a sufficient number of them have weak snow near the ground that will require extra testing which points to a MODERATE Avalanche Danger.

The Bridger Range:

Without new snow, the Bridger Range's instabilities are limited to a few slopes that have thinner and weaker snow. On Friday, Mark found facets on the west side of the range in Truman Gulch. I toured near Fairy and Frazier Lake on Sunday and confirmed that thin snowpacks are our weakest (video, snow pit, photo). Although facets can be found on many slopes, their ability to propagate a fracture varies. On the Football Field of Saddle Peak and in Truman Gulch test results were stable, but near Frazier they were unstable (ECTP 23&21, Q1). This variability falls in line with our other areas. Consequently, today's Avalanche Danger is rated MODERATE on all slopes.

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.