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. Also, see the Avalanche Advisory posted below.

Today: Cloudy with a 50 percent chance of snow. Southwest winds around 15 mph early in the morning becoming west around 15 mph late in the afternoon. Highs 30°F to 36°F.

Tonight: Partly cloudy. Lows 17°F to 23°F.

Saturday: Partly cloudy. Highs 34°F to 40°F.

Saturday Night: Mostly cloudy with a 30 percent chance of snow showers. Southwest winds around 15 mph. Lows 19°F to 25°F.

Sunday: Breezy. Snow showers likely. Snow accumulation of 3 to 6 inches. Southwest winds 15 to 20 mph. Chance of snow 70 percent. Highs 28°F to 34°F.

Sunday Night: Breezy...colder. Snow showers likely. Moderate snow accumulations. Chance of snow 60 percent. Lows 6°F to 12°F.

Monday: Mostly cloudy in the morning then becoming partly cloudy. A 20 percent chance of snow. Highs 23°F to 29°F.

Monday Night: Mostly clear. Lows 6°F to 12°F.

Tuesday: Mostly sunny. Highs 30°F to 36°F.

Tuesday Night: Mostly clear. Lows 14°F to 20°F.

Wednesday: Mostly cloudy with slight chance of snow in the morning...then partly cloudy with slight chance of snow... Possibly mixed with rain in the afternoon. Chance of precipitation 20 percent. Highs 32°F to 38°F.

Wednesday Night: Mostly cloudy with a 30 percent chance of snow. Lows 14°F to 20°F.

Thursday: Cloudy with a 40 percent chance of snow. Highs 26°F to 32°F.

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Mountain Weather

Since yesterday the Madison Range received 4 to 6 inches of low density snow. All other areas received 1 to 2 inches. This morning temperatures were in the low 20s Fahrenheit. Ridgetop winds in most areas were blowing westerly 10 to 15 mph with gusts up to 30 mph; however, in the Bridger Range and Hyalite Canyon winds were averaging 25 mph and gusting 30 to 40 mph from the West. Today will start mostly cloudy and dry as the day progresses with a brief ridge of high pressure building for Saturday. Temperatures should rise to the low 30s Fahrenheit and winds shouldn't change much. More snow will come Sunday.

Snowpack and Avalanche Discussion:

Bridger, Gallatin, and Madison Ranges, Lionhead Area near West Yellowstone, and Cooke City:

The combination of some new snow and steady winds means fresh wind slabs near ridgetops can be triggered today. Local ski patrols easily ski cut soft wind slabs yesterday. Fortunately this avalanche problem should be predictable. It is also easy to see and avoid.

Buried layers of weak faceted crystals are a more difficult problem. These layers are buried up to 3 feet deep and continue to produce avalanches clear warning signs (recent Bridger Range avalanche, and others). Several things make this layer tricky to manage today:

Spatial variability: These faceted layers exist throughout the advisory area (Madison Range video, Cooke City video). However, their distribution is not uniform. On some slopes they remain very weak. On others they are stronger while some slopes do not have these layers at all.

Difficult to trigger: Last weekend was last significant load of new snow. Since then, it has become more difficult to trigger an avalanche on these layers but the possibility is very real today. Hidden rocks are good trigger points as in this avalanche. Thin areas are also good places to trigger one (example in this video).

Good powder and supportable snow: With good powder on many slopes and very supportable conditions for snowmobiling, it is easy to forget about these layers which may be lurking beneath your skis, snowboard, or track. The only way to know if they exist is to pull out a shovel and dig 3 feet deep.

On Wednesday, Doug and Karl found these faceted crystals in the northern Gallatin Range on Mount Ellis. They had concerns along the ridge where wind-deposited snow added both stress and a cohesive slab. Lacking this slab and this load further down in the burned area, they felt comfortable skiing in avalanche terrain. HOWEVER, yesterday Eric and I investigated a natural avalanche nearby on Mount Wheeler (photo, crown profile) where the terrain is generally steeper and experiences more wind. This slide likely occurred last Sunday following significant snowfall. More snow is expected this Sunday and similar slides could easily happen if any significant snowfall occurs.

Don't be discouraged. You can ride all day long on slopes less than 30 degrees with minimal avalanche concerns. Also, you can definitely find stable slopes but it takes work (i.e. several snowpits and multiple stability tests) to ensure you've found one. Unfortunately with wind slabs near ridgetops and weak layers of facets in the snowpack, triggering an avalanche remains possible. For this reason today the Avalanche Danger is rated MODERATE.

Minimizing False-Stable Test Results:

Already this season all three of us have gotten false-stable tests results, which are a bit scary. Stability tests are not 100% accurate and scores showing stability when things are unstable is dangerous, which happen about 10% of the time. This is why we dig multiple snowpits. Karl Birkeland and I studied this "false-stable" problem and made a presentation at the 2006 International Snow Science workshop which you can read HERE.

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

EDUCATION, PHOTOS, SNOWPITS, and VIDEOS

1. For links to Articles, Education and (photos), (snowpits), or (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.