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: Mostly sunny. Patchy freezing fog in the morning. Highs 21°F to 27°F.

Tonight: Mostly clear in the evening then becoming partly cloudy. Lows -5°F to 5°F.

Sunday: Partly cloudy in the morning then becoming mostly cloudy. Southwest winds around 15 mph late in the afternoon. Highs 21°F to 27°F.

Sunday Night: Cloudy. Chance of snow in the evening...then slight chance of snow after midnight. Southwest winds around 15 mph in the evening. Chance of snow 30 percent. Lows 1°F to 7°F.

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

Monday Night: Mostly cloudy with a 30 percent chance of snow. Lows 9°F to 15°F.

Tuesday: Mostly cloudy with a 40 percent chance of snow. Highs 21°F to 27°F.

Tuesday Night: Mostly cloudy with a 30 percent chance of snow. Lows 13°F to 19°F.

Wednesday: Mostly cloudy with a 40 percent chance of snow. Highs 24°F to 30°F.

Wednesday Night: Mostly cloudy with a 40 percent chance of snow. Lows 9°F to 15°F.

Thursday: Mostly cloudy with a 40 percent chance of snow. Highs 15°F to 21°F.

Thursday Night: Colder. Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of snow. Lows -6°F to 0°F.

Friday: Mostly cloudy with a 20 percent chance of snow in the morning...then partly cloudy in the afternoon. Highs 10°F to 16°F.

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Mountain Weather

This morning valley temperatures were in the single digits Fahrenheit (West Yellowstone had -20 Fahrenheit) while mountain temperatures were mostly in the low teens Fahrenheit with slightly warmer temperatures in the Bridger Range. Winds were blowing westerly 10 to 15 mph with gusts of 20 mph. Today, a short lived ridge of high pressure will bring sunny skies and temperatures near 32 degrees Fahrenheit. Winds may ease a bit and today will a good one to be in the mountains. Clouds will return Sunday afternoon with a chance for snow and a better chance late Monday.

Snowpack and Avalanche Discussion:

The Bridger Range:

On Thursday a skier triggered and was caught in an avalanche in the Hourglass chute just north of Bridger Bowl. It was a wind slab that broke about 75 feett wide, 1 foot deep and ran 1000 feet vertical. Fortunately he was only partially buried and not seriously injured. While investigating the slide yesterday, I felt that this chute was one of the few places in that area with unstable snow. Eric put it best "The hourglass is a catcher's mitt for wind-blown snow from all directions." Watch a video of the avalanche, a video of our investigation, and photo1 and photo2.

On an adjacent slope we found weak facets 6 inches below the surface (snowpit), but this layer did not fracture in our stability tests because it did not have a slab on it. The Hourglass produced an avalanche because it had a wind slab on this weak layer. While many adjacent slopes lacked this slab and were stable, other slopes in the Bridger Range may have a wind slab on a similar weak layer. Today wind loaded terrain, steeper than 35 degrees has heightened avalanche conditions and a MODERATE Avalanche Danger. All other terrain has a LOW Avalanche Danger.

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

The last notable snowfall occurred 10 days ago. Without the stress of new snow, the snowpack is mostly stable, but there is one avalanche problem to consider. During recent dry weather, the snow surface faceted and weakened in many places but not all. Early this week, winds affected many exposed slopes, and some may have a thin wind slab resting on the near surface facets. In Bear Basin on Thursday, I couldn't find this combination and felt comfortable skiing steep terrain. Nearby at Big Sky a small point release on a South facing slope triggered a thin wind slab resting on near surface facets, a clear sign this combination exists and can produce an avalanche. With generally safe avalanche conditions and unstable snow only in isolated locations, today the Avalanche Danger is LOW.

* * NEW WEAK LAYER * *

Recent dry weather with warm sunny days and clear cold nights weakened and faceted the snow surface in many areas. See this video. How does this happen? The snow surface temperature can vary widely between day and night while the temperature only 10 to 12 inches down does not. The result is a big temperature difference over a short distance which changes snow crystals into weak and angular facets. What does this mean for the future? With more snow in the forecast, this new weak layer will be buried and preserved. Once a slab of snow builds on top of it, we'll have the right recipe for avalanches.

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 Articles, Education and (photos) and (videos) listed in the above report, please visit this Link.

2. They have recently uploaded more photos and snowpits to their web site, more than what are linked in the advisory above.

3. They have creating a series of "How To…" stability test videos. So far they have clips on performing a CT and ECT. They are located under Stability Tests on their 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.