Today...Breezy...snow. Areas of blowing snow. Snow accumulation of 2 to 6 inches. Highs 27°F to 33°F. Southwest winds 15 to 25 mph with gusts to around 40 mph. Chance of snow near 100 percent.

Tonight...Breezy. Snow in the evening...then snow likely after midnight. Snow accumulation of 1 to 2 inches. Total snow accumulation 3 to 12 inches. Lows 8°F to 14°F. West winds 15 to 20 mph. Chance of snow near 100 percent.

Sunday...Breezy...cloudy. Chance of snow in the morning...then slight chance of snow in the afternoon. Highs 18°F to 24°F. Southwest winds 15 to 20 mph with gusts to around 35 mph. Chance of snow 40 percent.

Sunday Night...Breezy. Cloudy with a 50 percent chance of snow. Lows 5°F to 11°F. Southwest winds 15 to 20 mph.

Monday...Snow likely. Snow accumulation of 1 to 2 inches. Highs 22°F to 28°F. Southwest winds around 15 mph. Chance of snow 70 percent.

Monday Night...Mostly cloudy with chance of snow in the evening... Then partly cloudy with slight chance of snow after midnight. Lows 6°F to 12°F. Chance of snow 40 percent.

Tuesday...Partly cloudy. Highs 19°F to 25°F.

Tuesday Night...Partly cloudy. Slight chance of snow showers in the evening...then chance of snow showers after midnight. Lows 8°F to 14°F. Chance of snow 40 percent.

Wednesday...Not as cold. Mostly cloudy with a 40 percent chance of snow. Highs 27°F to 33°F.

Wednesday Night...Mostly cloudy with a 40 percent chance of snow. Lows 16°F to 22°F.

Thursday...Mostly cloudy with a 50 percent chance of snow. Highs 28°F to 34°F.

Thursday Night...Colder. Mostly cloudy in the evening then becoming partly cloudy. A 50 percent chance of snow. Lows 8°F to 14°F.

Friday...Partly cloudy with a 20 percent chance of snow. Highs 21°F to 27°F.

♦ WINTER STORM WARNING ♦

A Winter Storm Warning remains in effect from 11:00 PM Friday evening to 11:00 PM MST Saturday.

* Summary and timing...snow will continue to overspread Yellowstone early tonight...becoming heavy at times after midnight. The heaviest snowfall is expected between 4:00 am and 10:00 am Saturday...and mainly impact the southwest quarter of the park.

* Snow accumulations...2 to 4 inches in the north with 8 to 12 inches in the mountains...and locally higher amounts approaching 18 inches possible in the south.

* Wind and visibility...southwest winds 25 to 35 mph with gusts in excess of 50 mph over higher peaks...becoming west by Saturday evening. Visibility will be reduced to near zero at times.

* Impacts...outdoor activities and travel may become extremely treacherous as the strong winds and heavy snow combine to produce whiteout conditions.

Precautionary/preparedness actions...

A Winter Storm Warning for heavy snow means severe winter weather conditions are expected or occurring. Significant amounts of snow are forecast that will make travel dangerous. Only travel in an emergency. If you must travel...keep an extra flashlight... food... and water in your vehicle in case of an emergency.

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

♦ AVALANCHE WARNING ♦

The Gallatin National Forest Avalanche Center continues a Backcountry Avalanche Warning for the Lionhead area near West Yellowstone and the mountains around Cooke City. Heavy snow continues to fall on an extremely weak snowpack causing unstable conditions. Today, natural and human triggered avalanches are likely and the Avalanche Danger is HIGH on all slopes. Areas of unstable snow exist. Natural and human triggered avalanches are likely. Avalanche terrain including avalanche run out zones should be avoided.

Mountain Weather

A strong westerly flow continues to usher pacific moisture into southwest Montana. Since yesterday another 4 to 6 inches of high density snow has fallen in the mountains around Cooke City and West Yellowstone while the mountains around Big Sky picked up an additional 2 to 3 inches. Unfortunately the mountains around Bozeman have remained dry.

At 4:00 AM temperatures are in the mid to high 20s Fahrenheit and winds are blowing 20-30 mph out of the West-southwest with gusts in the 50s being recorded in the northern Gallatin and Madison Ranges. Today, an unsettled weather pattern will continue with an additional 4 to 6 inches possible in the southern ranges and 2 to 3 inches in the north. Temperatures will rise into the mid 30s Fahrenheit and winds will stay moderate to strong out of the West-southwest.

Snowpack and Avalanche Discussion:

The Lionhead area near West Yellowstone and the mountains around Cooke City:

Near West Yellowstone and Cooke City, the story is simple. Heavy snowfall and high winds have created very dangerous avalanche conditions. Storm totals over the past four days equal:

• 4 inches of SWE, totaling over 3 feet of snow, in the mountains around Cooke City.


• 2.9 inches of SWE, totaling over two feet of snow, in the mountains around West Yellowstone.

This heavy load has been deposited on top of a very weak snowpack resulting in highly unstable conditions. Any slope that has received additional loading due to wind will be more susceptible to both natural and human triggered avalanches.

Today the message is clear - if you play in avalanche terrain you will likely find avalanches. During dangerous conditions such as these, it is possible to trigger slides from a distance including from the bottom of the slope. Even small, unassuming slopes can have large consequences, especially if associated with terrain traps.

Today, the Avalanche Danger is rated on HIGH on all slopes and travel in avalanche terrain is not recommended.

The southern Madison and southern Gallatin Ranges:

The southern Madison and southern Gallatin Ranges have not received as much snow as the mountains around Cooke City and West Yellowstone. However, storm totals of over a foot combined with strong winds are adding a tremendous amount of stress to a very weak snowpack.

Yesterday, riders in Cabin Creek and Tepee Basin in the southern Madison Range observed numerous natural and human triggered avalanches and found unstable results in their stability tests. I found similar conditions in the Sothern Madison Range on Thursday.

While wind loaded slopes are the primary avalanche concern, non-wind loaded slopes also have the capability of producing avalanches.

Today, very dangerous avalanche conditions exist on wind loaded slopes where the Avalanche Danger is rated HIGH. Non-wind loaded slopes have a CONSIDERABLE Avalanche Danger.

The northern Madison and northern Gallatin Ranges:

Yesterday, my partners and I toured into Beehive Basin and found four inches of high density snow resting over a variety of weak layers. While four inches does not seem like a lot, it was enough to produce obvious signs of instability such as cracking and collapsing. We also sympathetically triggered a slide with a cornice drop, confirmation unstable conditions were present.

Today, the primary avalanche concern will be any slope that is wind loaded. Prior to the storm, strong winds created spatially variable hard slabs that are now buried under the new snow. These slabs may be difficult to pick out visually but will often reveal themselves with a loud collapse. Wind slabs formed during or immediately after the storm will be of the softer variety and will easily fail under the weight of a skier or rider. Triggering one of these wind slabs can easily cause an avalanche to break deeper in the snowpack or even at the ground.

The Hyalite Drainage in the northern Gallatin Range deserves a special mention because it has more stable conditions. Recently formed wind slabs could produce and avalanche, but the overall likelihood of triggering a slide is less in this area.

Today, human triggered avalanches are likely on all wind slopes which have CONSIDERABLE Avalanche Danger. Slopes without a wind load have a MODERATE Avalanche Danger.

The Bridger Range:

Over the past four days the Bridger Range has received 1 to 2 inches of new snow. The lack of precipitation has done little to improve skiing and riding conditions, but it has helped reduce the avalanche danger.

Yesterday, the Bridger Bowl Ski Patrol did not receive any notable results during control work. They also mentioned avalanche observations around the area have been minimal. However, strong winds prior to the storm did produce stiff wind slabs which could be triggered by a skier or rider. Steep, rocky terrain, specifically below ridgelines will be the most like areas to find unstable snow.

Today, human triggered avalanche 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.

Beacon Parks

The Friends of the Avalanche Center installed a Beacon Training Park outside West Yellowstone last Friday. It's located south of town on the main snowmobile trail. Stop by and do a quick practice before heading off into the mountains!

EDUCATION, EVENTS, 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.

3. Check out all our education programs, Click Here.

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.