Today...Windy...snow. Snow accumulation of 1 to 3 inches. Highs 30°F to 36°F. Southwest winds 20 to 30 mph. Chance of snow near 100 percent.

Tonight...Breezy. Snow likely in the evening...then snow after midnight. Snow accumulation around 1 inch. Lows 17°F to 23°F. Southwest winds 20 to 25 mph with gusts to around 40 mph shifting to the west 15 to 20 mph in the late evening and overnight. Chance of snow 90 percent.

Friday...Breezy. Snow in the morning...then snow and rain in the afternoon. Snow accumulation of 1 to 2 inches. Highs 29°F to 35°F. Southwest winds 15 to 25 mph. Chance of precipitation near 100 percent.

Friday Night...Windy...snow. Snow accumulation of 2 to 3 inches. Lows 11°F to 17°F. Southwest winds 25 to 30 mph shifting to the west 15 to 25 mph after midnight. Chance of snow near 100 percent.

Saturday...Breezy...colder...cloudy. Snow likely in the morning... Then chance of snow in the afternoon. Snow accumulation around 1 inch. Total snow accumulation 7 to 13 inches. Highs 16°F to 22°F. West winds 15 to 20 mph. Chance of snow 70 percent.

Saturday Night...Colder. Mostly cloudy with a 20 percent chance of snow in the evening...then partly cloudy after midnight. Lows -4°F to 2°F. Wind chill readings -16°F to -26°F.

New Years Day...Partly cloudy. Highs 19 to 25. Lowest wind chill readings -10°F to -20°F in the morning.

Sunday Night...Partly cloudy. Lows 2°F to 10°F.

Monday...Partly cloudy. Highs 26°F to 32°F.

Monday Night...Partly cloudy. Lows 8°F to 14°F.

Tuesday...Partly cloudy. Highs 23°F to 29°F.

Tuesday Night...Partly cloudy. Lows 7°F to 13°F.

Wednesday...Partly cloudy. Highs 23°F to 29°F.

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

Mountain Weather

Since yesterday the mountains near Cooke City received 7-9 inches of snow and the mountains near Big Sky, the Taylor Fork and West Yellowstone received 4-5 inches. Near Bozeman, the northern Gallatin Range received 1 inch and the Bridger Range received none. All areas have temperatures near 30 degrees Fahrenheit and very strong winds blowing 15-30 mph from the W with gusts of 40-50 mph. Today temperatures should drop to near 20 degrees Fahrenheit by afternoon and strong winds will continue. A little more snow will fall this morning, then snow will return tonight and through Friday. By tomorrow morning most areas especially mountains from Big Sky south will receive 1-3 inches of snow.

Snowpack and Avalanche Discussion:

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

The entire Madison Range, the southern Gallatin Range and the mountains near West Yellowstone received 4-5 inches of new snow overnight on top of a few inches from yesterday. While this storm didn't provide much snow, it provided very strong West winds. Most slopes have been affected by these winds; some scoured and some loaded. In these areas the snowpack is like an all-you-can-eat buffet of weak snow. Depth hoar crystals exist at the ground, near surface facets exist just under the new snow, and on some slopes one or two layers of surface hoar can be found. Avalanches have numerous weak layers on which they can break. Today's snow and wind have provided the slab. The final ingredient needed for an avalanche is a trigger which could be a skier, rider, or more snow.

As more snow falls and winds continue, avalanches will become easier to trigger and could break over progressively larger areas. Even non wind loaded slopes are approaching their breaking point evidenced by a small slide following last week's storm in Beehive Basin. For today a CONSIDERABLE Avalanche Danger exist on all slopes.

The mountains around Cooke City:

Near Cooke City, the snowpack lacks the smorgasbord of weak layers found in other areas. Instabilities will be confined to the new snow, but avalanches are just as likely with 7-9 inches of new snow and strong winds. Even slopes unaffected by the wind may have warm, dense snow overlying lighter, cold snow which is a good recipe for an avalanche. Today all wind loaded slopes and all slopes steeper than 35 degrees have a CONSIDERABLE Avalanche Danger. Slopes without a wind load (which are very few) and less than 35 degrees have a MODERATE Avalanche Danger.

The Bridger Range and northern Gallatin Range:

No snow fell in the mountains near Bozeman. To make matters worse the Bridger Range received a slight drizzle of rain. With no new snow and no load, the snowpack in the Bridger Range remains in its holding pattern. It is a very weak snowpack but lacks the stress of new snow to create avalanches. Yesterday the Bridger Bowl Ski Patrol tested several slopes with explosives near the Slushman's Lift where the snowpack has backcountry conditions. They were not able to trigger avalanches.

The northern Gallatin Range has a similarly weak snowpack on Mt Ellis, but a completely different snowpack in Hyalite Canyon where the snowpack is stronger and deeper. While there is little snow available to be transported by winds, they have blown especially strong in these areas. Today it is possible to trigger an avalanche on slopes that have been wind loaded where the Avalanche Danger is MODERATE. Until more snow falls all other slopes have a LOW Avalanche Danger.

This morning is warm and windy with fresh snowfall in the southern mountains. Four inches has fallen near Cooke City with 1-2 inches accumulating from the Yellowstone Club to West Yellowstone. Mountain temperatures are in the mid to high 20s Fahrenheit as westerly winds average 30-40 mph with gusts hitting 50 mph. The jet stream will keep winds strong and create favorable dynamics for snowfall. By morning there could be 1-2 inches in the northern mountains and 6-8 inches in the southern ranges.

I will issue 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. We've recently uploaded more photos and snowpits to our web site, more than what are linked in the advisory.

2. 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 Events and Education, or 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.