Today...Breezy. Snow in the morning...then snow likely in the afternoon. Snow accumulation up to 1 inch. Highs 24°F to 30°F. Southwest winds 15 to 20 mph. Chance of snow 80 percent.

Tonight...Breezy. Snow likely in the evening...then snow after midnight. Snow accumulation of 1 to 4 inches. Lows 17°F to 23°F. Southwest winds 15 to 25 mph. Gusts up to 40 mph. Chance of snow 90 percent.

Saturday...Breezy...snow. Areas of blowing snow. Snow accumulation of 3 to 5 inches. Highs 26°F to 32°F. Southwest winds 15 to 25 mph. Chance of snow near 100 percent.

Saturday Night...Breezy...colder. Snow likely. Snow accumulation of 1 to 2 inches. Total snow accumulation 6 to 19 inches. Lows 8°F to 14°F. Southwest winds 15 to 20 mph. Chance of snow 60 percent.

Sunday...Breezy. Cloudy with a 50 percent chance of snow. Highs 17°F to 23°F. West winds 15 to 20 mph.

Sunday Night...Mostly cloudy with a 40 percent chance of snow. Lows 5°F to 11°F.

Monday...Chance of snow in the morning...then snow likely in the afternoon. Highs 21°F to 27°F. Chance of snow 60 percent.

Monday Night...Mostly cloudy in the evening then becoming partly cloudy. A 50 percent chance of snow. Lows 4°F to 10°F.

Tuesday...Partly cloudy with a 20 percent chance of snow. Highs 18°F to 24°F.

Tuesday Night...Partly cloudy with a 40 percent chance of snow. Lows 6°F to 12°F.

Wednesday...Mostly cloudy with a 40 percent chance of snow. Highs 23°F to 29°F.

Wednesday Night...Mostly cloudy with a 50 percent chance of snow. Lows 13°F to 19°F.

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

♦ WINTER STORM WARNING ♦

A Winter Storm Warning remains in effect from 11:00 PM this 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. Avalanches were triggered yesterday and more will occur. Today 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

Since yesterday morning the Lionhead area near West Yellowstone and the mountains near Cooke City received 11 to 15 inches of new snow. The southern Madison Range received 6 inches, northern Madison Range near Big Sky received 3 to 5 inches, and the mountains near Bozeman received 1 to 2 inches. This morning temperatures at 9000 feet were in the low 20s Fahrenheit. Ridgetop wind were averaging 10-20 mph from the West and Southwest with gusts of 35 mph. Hyalite is the exception with winds averaging 30 mph and gusting to 50 mph.

Another few inches of snow may fall this morning, but snowfall will end today. More snow should return late tonight mostly in the southern areas which will have another inch or two by tomorrow morning. Winds today will be relatively calm blowing 15-30 mph from the West and Southwest but increase again this evening. Temperatures will remain in the low 20s Fahrenheit at higher elevations but warm to the low 30s Fahrenheit in the valleys.

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.

• In the last 24 hours these areas received 1.1 to 1.5 inches of snow water equivalent (SWE) which is about 11 to 15 inches of snow.

• In the last 3 days, the mountains near Cooke City received 3.3 inches of SWE, and the Lionhead area near West Yellowstone received 2.3 inches of SWE.

Yesterday Doug and his partner triggered several avalanches along Lionhead ridge some with cornice drops and another remotely. Further north near Hebgen Lake, Eric and his partners also triggered an avalanche remotely. Remotely triggered avalanches are a clear indication of very unstable conditions. A skier near Cooke City triggered an avalanche in wind loaded gully while skiing the adjacent low angle slope. He also observed another one triggered by a falling cornice. Those avalanches occurred yesterday. Since then, more snow has fallen and more avalanches will occur today.

Avoid avalanche terrain but also avoid avalanche run out zones where you can trigger and be caught in an avalanche. Many avalanche fatalities have occurred near West Yellowstone and Cooke City by people in run out zones. Today the Avalanche Danger is HIGH.

The Bridger, Madison and Gallatin Ranges:

The Bridger, Madison, and Gallatin Ranges have received less snow but plenty of strong wind which has formed many hard wind slabs. Triggering one of these wind slabs can easily cause an avalanche to break deeper in the snowpack or even at the ground. Avoiding these wind slabs is the key to avoiding avalanches, but this will be hard to do. Many of these wind slabs have been covered by last night's snowfall and might be difficult to find visually.

Don't let your guard down on non-wind loaded slopes especially in the Madison Range which received about 0.4 to 0.6 inches of SWE. While this snowfall may not seem like much, the snowpack is very weak on many slopes and may struggle to support even this small load. Today all wind loaded slopes have a CONSIDERABLE Avalanche Danger. Non-wind loaded slopes have a MODERATE Avalanche Danger.

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.