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: Breezy...cloudy. Snow likely in the morning...then scattered snow showers in the afternoon. Snow accumulation of 1 to 2 inches. Southwest winds 15 to 25 mph. Chance of snow 60 percent. Highs 22°F to 28°F.

Tonight: Cloudy. Chance of snow in the evening...then snow after midnight. Snow accumulation of 1 to 3 inches. South winds around 15 mph. Chance of snow 80 percent. Lows 7°F to 13°F.

Monday: Snow in the morning...then numerous snow showers in the afternoon. Snow accumulation of 2 to 4 inches. Southwest winds around 15 mph. Chance of snow 80 percent. Highs 19°F to 25°F.

Monday Night: Colder...cloudy. Snow likely in the evening...then chance of snow after midnight. Snow accumulation around 1 inch. Total snow accumulation 5 to 14 inches. Northwest winds around 15 mph in the evening. Chance of snow 60 percent. Lows -3°F to 3°F.

Christmas Day / Tuesday: Mostly cloudy in the morning then becoming partly cloudy. Southwest winds around 15 mph in the afternoon. Highs 13°F to 19°F. * Merry Christmas *

Christmas Night / Tuesday Night: Partly cloudy with a 20 percent chance of snow. Lows 0°F to 6°F. Lowest wind chill readings -10°F to -20°F after midnight. * Merry Christmas *

Wednesday: Partly cloudy with slight chance of snow in the morning...then mostly cloudy with chance of snow in the afternoon. Chance of snow 30 percent. Highs 18°F to 24°F.

Wednesday Night: Cloudy with a 50 percent chance of snow. Lows 6°F to 12°F.

Thursday: Mostly cloudy with a 40 percent chance of snow. Highs 18°F to 24°F.

Thursday Night: Mostly cloudy with a 30 percent chance of snow. Lows 3°F to 9°F.

Friday: Mostly cloudy with a 20 percent chance of snow. Highs 16°F to 22°F.

Friday Night: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of snow. Lows -1°F to 7°F.

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

 Hazardous Weather Forecast  Gibbon Falls Forecast  Mammoth Forecast  Midway Forecast  Norris Forecast  Old Faithful Forecast 

Mountain Weather

Overnight a fast moving weather disturbance dropped 2 to 3 inches of snow in the mountains around West Yellowstone and Cooke City including the southern Madison Range. The mountains around Bozeman and Big Sky picked up a trace to one inch. Currently, temperatures are in the teens Fahrenheit and winds are blowing 10 to 20 out of the South-southwest with gusts reaching close to 30 mph. Today, highs will climb into the 20s Fahrenheit under partly to mostly cloudy skies. Winds will continue to blow 10 to 20 from the South-southwest. A more potent storm will impact our area tonight and tomorrow. 1 to 3 inches is possible by morning with 4 to 6 inches likely by tomorrow afternoon.

Snowpack and Avalanche Discussion:

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

Weather is the architect of avalanches. Precipitation, wind and temperature all play a crucial role in snowpack development. Over the past few days, the storms have eased and the winds have picked up. This has created a more variable snowpack than the one we were dealing with just a week ago. As one experienced backcountry skier put it yesterday - The skiing went from hero to zero in three days. He was describing conditions in a more alpine setting, but the fact is - the snowpack continues change.

Avalanche Problem # 1: Wind Slabs

Over the past 48 to 72 hours, strong South-southwest winds have stripped windward slopes, redistributing heavy amounts of snow onto north and east aspects. Dense, nearly supportable wind slabs can be found on the lee side of upper elevation slopes, mainly below ridgelines and cross loaded terrain features. These slabs could be resting over weaker, low density snow making them susceptible to human triggers. Round, hardened wind pillows will be features to recognize and avoid.

In areas that received new snow, shallow soft slabs will found on leeward slopes near ridgelines and in cross loaded gullies. Fresh wind slabs will be sensitive to human triggers, but should stay relatively small in size.

Avalanche Problem # 2: Buried Persistent Weak Layers

Over the past few days, large natural avalanches have been observed in the northern Bridger Range. These slides occurred on wind loaded slopes, but went above and beyond typical wind slabs. Deep crown lines and good propagation indicate these slides failed on buried facets formed earlier in the season. Buried persistent weak layers are not widespread, but continue to make their presence known. Upper elevation slopes, specifically those with shady aspects (north through east) appear to be holding the weakest snow near the ground. Areas where the snowpack is non-uniform - mainly in upper elevation, rocky terrain will be likely areas to trigger a deeper slide (photo, photo, photo).

In areas where the snowpack is uniform and more than a meter deep, generally strong and stable conditions exists (photo).

A future problem is the surface snow that has become faceted over the past few days of calm, clear weather. This problem does not exist on all slopes, but is something to keep in mind as more storms impact the area. Mark found weak surface snow on the west side of the Bridgers on Friday and I found near surface facets forming on Mount Ellis Yesterday.

Today, human triggered avalanches remain possible and the Avalanche Danger is rated MODERATE.

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.