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. Chance of snow showers through the day. Chance of rain showers early in the afternoon. Highs 30 to 36. Chance of precipitation 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. A 40 percent chance of snow. Lows 13 to 19.

Saturday: Partly cloudy. Highs 26 to 32.

Saturday Night: Partly cloudy. Lows 8 to 14.

Sunday: Mostly sunny. Highs 31 to 37.

Sunday Night: Partly cloudy. Lows 14 to 20.

Monday: Partly cloudy in the morning then becoming mostly cloudy. A 20 percent chance of snow. Highs 30 to 36.

Monday Night: Mostly cloudy with a 40 percent chance of snow. Lows 19 to 25.

Tuesday: Mostly cloudy. Chance of snow in the morning...then chance of snow...possibly mixed with rain in the afternoon. Highs 32 to 38. Chance of precipitation 40 percent.

Tuesday Night: Mostly cloudy with a 30 percent chance of snow. Lows 18 to 24.

Wednesday: Partly cloudy with a 20 percent chance of snow. Highs 33 to 39.

Wednesday Night: Partly cloudy with a 20 percent chance of snow. Lows 18 to 24.

Thursday: Partly cloudy in the morning...then mostly cloudy with slight chance of rain and snow in the afternoon. Highs 36 to 42. Chance of precipitation 20 percent.

All Temperatures (Highs and Lows) are in degrees Fahrenheit (°F). All Sub Zero Temperatures are Highlighted.

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Mountain Weather

Overnight the mountains near Cooke City and West Yellowstone received an inch of new snow. A few other areas got a trace. This morning temperatures were near 20 degrees Fahrenheit. Winds were blowing 5 to 10 mph from the South with gusts of 15 mph – surprisingly calm for Southwest Montana. Today mostly cloudy skies will keep temperatures from rising above freezing and winds will remain calm. The mountains near Big Sky and West Yellowstone could get an inch of snow while Cooke City could get a few inches. This weekend should have calm winds and sunny skies with a chance of snow for Monday.

Snowpack and Avalanche Discussion:

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

Wind slabs yesterday were mostly unreactive and generally well bonded to the underlying snow. The lead climbing ranger and forecaster from Mount Shasta joined me for a ride in the southern Madison Range through Teepee Basin, Cabin Creek, and Sage Basin. We cut lots of fresh drifts on steep rollovers but none moved or even cracked – a good sign. Local ski patrols reported similar conditions. Watch out, because wind slabs have a habit of catching us off guard.

Layers of facets in the upper 3 feet of the snowpack continue to propagate fractures in stability tests as Doug found south of Hebgen Lake (video) yesterday. North of Hebgen Lake, these layers propagated about a third of the time in our stability tests. Propagation is the second step to get an avalanche. The first step is fracture initiation which depends on the balance between stress and strength. To initiate a fracture, find a place where the snowpack is stressed (like near big drift of wind-blown snow) or find a place where the faceted layers are weaker. Weak places often exist near rocks or cliff bands and are called sweet spots or trigger points by ski patrollers. At a ski area, they know where these points exist.

We don't know where these trigger points exist in the backcountry. For this reason, it's worth digging a few snowpits only 3 feet deep to assess these faceted layers. Watch this video if you are snowmobiling. These layers are variable which can be an advantage. It means we can find slopes where these layers either don't exist or where they don't propagate fractures. For today stubborn wind slabs and buried weak layers mean human triggered avalanches are possible and the Avalanche Danger is rated MODERATE.

Another problem: Cornices are currently very large and often break closer to ridgelines than expected. A very experienced skier and avalanche professional had a large cornice break between his legs yesterday even though he was far from the edge (photo). Had he fallen with it, he was certain that he would have died.

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.