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: Mostly cloudy with isolated snow showers. Southwest winds around 15 mph in the afternoon. Chance of snow 20 percent. Highs 20°F to 26°F. Lowest wind chill readings -10°F to -20°F in the morning.

Tonight: Mostly cloudy with isolated snow showers. Southwest winds around 15 mph until early morning. Chance of snow 20 percent. Lows 4°F to 10°F.

Thursday: Mostly cloudy with scattered snow showers. Southwest winds around 15 mph in the afternoon. Chance of snow 50 percent. Highs 23°F to 29°F.

Thursday Night: Mostly cloudy with scattered snow showers. Southwest winds around 15 mph in the evening. Chance of snow 30 percent. Lows 11°F to 17°F.

Friday: Mostly cloudy in the morning then becoming partly cloudy. Isolated snow showers. Chance of snow 20 percent. Highs 28°F to 34°F.

Friday Night: Partly cloudy. Lows 14°F to 20°F.

Saturday: Mostly sunny. Highs 35°F to 41°F.

Saturday Night: Partly cloudy. Lows 17°F to 23°F.

Sunday: Breezy. Mostly cloudy with a 50 percent chance of snow. Highs 29°F to 35°F.

Sunday Night: Mostly cloudy with a 50 percent chance of snow. Lows 11°F to 17°F.

Monday: Mostly cloudy with a 30 percent chance of snow. Highs 23°F to 29°F.

Monday Night: Partly cloudy with a 20 percent chance of snow. Lows 6°F to 12°F.

Tuesday: Partly cloudy. Highs 26°F to 32°F.

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Mountain Weather

Under partly cloudy skies there's no new snow to report. Yesterday, temperatures reached the 20s Fahrenheit as winds calmed throughout the day. This morning, mountain temperatures are in the single digits Fahrenheit with light ridgetop winds out of the west to southwest (15 to 20 mph). Skies will remain partly cloudy with light winds and temperatures warming into the low 20s Fahrenheit. Tonight will become mostly cloudy, but offer no real chance of snow.

Snowpack and Avalanche Discussion:

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

Mark and his partner skied around Beehive and Bear Basins yesterday. What he found is indicative of the conditions throughout southwest Montana and his tour offers a few key lessons on the snowpack and travel.

Lesson 1: The weakest layer in the snowpack (sugary facets), will be found in the upper three feet (video). Other than slopes holding a thin snowpack, you do not need to dig to the ground to find this.

Lesson 2: Many slopes are stable and offer good skiing and riding. Either slopes lack a significant weak layer or the layer has strengthened and will not break in our stability tests. Mark found this on east facing slopes in Bear Basin.

Lesson 3: If the snow structure looks weak (i.e. a layer of weak, large-grained facets supporting a dense wind slab) yet stability tests show strength, dig another pit. Do not be afraid to throw out stable tests results in a structurally weak snowpack since they represent "false-stable" conditions (article). Mark found a slope in Beehive with one foot of weak facets underlying a two foot slab. His tests showed stability but he did not believe it (snowpit). An hour later he visited Big Sky Snow Safety and learned they triggered a 100-foot wide avalanche with an identical structure and aspect (photo).

Lesson 4: Slopes adjacent to avalanches are also unstable. This lesson comes from Cooke City where a snowmobiler triggered an avalanche right next to a large slide that released last Tuesday (photo). On slopes with recent avalanche activity there's no need to dig a snowpit because avalanches are the number one sign that slopes are prone to slide.

In general the snowpack is not looking too bad, nor is it looking great. You can still trigger avalanches if you hit just the wrong spot. Evidence includes avalanche activity over the last week in the Bridger Range, Lionhead and Cooke City, instability in our snowpits and Mark's concise findings from yesterday. These all point to a MODERATE Avalanche Danger.

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.