Today...Windy. Snow in the morning...then snow and rain in the afternoon. Areas of blowing snow through the day. Snow accumulation of 4 to 6 inches. Southwest winds 25 to 35 mph with gusts to around 50 mph. Chance of precipitation near 100 percent. Highs 32°F to 38°F.

Tonight...Windy. Snow showers in the evening...then snow after midnight. Areas of blowing snow through the night. Snow accumulation of 1 to 3 inches. West winds 25 to 35 mph with gusts to around 55 mph decreasing to 20 to 25 mph after midnight. Chance of snow near 100 percent. Lows 5°F to 11°F.

Thursday...Breezy...colder. Snow likely in the morning...then numerous snow showers in the afternoon. Snow accumulation of 1 to 2 inches. Total snow accumulation 7 to 16 inches. West winds 15 to 20 mph. Chance of snow 70 percent. Highs 19°F to 25°F.

Thursday Night...Breezy...colder. Mostly cloudy. Chance of snow in the evening...then slight chance of snow after midnight. West winds 15 to 20 mph. Chance of snow 30 percent. Lows -2°F to 4°F. Wind chill readings -10°F to -20°F.

Friday...Breezy. Mostly cloudy with a 20 percent chance of snow. Southwest winds 15 to 20 mph in the afternoon. Highs 23°F to 29°F.

Friday Night...Mostly cloudy with a 40 percent chance of snow. Lows 9°F to 15°F. Lowest wind chill readings -10°F to -20°F after midnight.

Saturday...Cloudy with a 50 percent chance of snow. Highs 24°F to 30°F.

Saturday Night...Mostly cloudy with a 50 percent chance of snow. Lows 5°F to 11°F.

Sunday...Mostly cloudy with a 40 percent chance of snow. Highs 19°F to 25°F.

Sunday Night...Mostly cloudy with a 40 percent chance of snow. Lows -0°F to 6°F.

Monday...Mostly cloudy with a 30 percent chance of snow. Highs 17°F to 23°F.

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

Tuesday...Partly cloudy. Highs 18°F to 24°F.

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  ♦  ♦  Backcountry Avalanche Warning  ♦  ♦  

The Gallatin National Forest Avalanche Center is issuing a Backcountry Avalanche Warning for the Bridger Range. Heavy snowfall, high winds and an extremely weak snowpack are causing unstable conditions. 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 runout zones should be avoided.

This warning will either be terminated or updated by 6:00 AM on February 23, 2012.

Mountain Weather

During the last 24 hours snow fell, winds blew and temperatures warmed. Since yesterday morning the mountains got 4 to 10 inches of new snow with varying densities. The Bridger Range has gotten 6 inches of 20% density snow (1.2 inches Snow Water Equivalency or SWE); the northern Gallatins, Big Sky area and West Yellowstone received about 5 inches of new (.7-.9 inches SWE) and Cooke City has about 10 inches (1.4 inches SWE). Higher elevations were colder than the measuring stations. Colder air makes lower density powder with the same water equivalency, so expect substantially more snow the higher you go. Winds are blowing out of the west at 30-60 mph with mountain temperatures in the mid to high 20s Fahrenheit. The storm will continue today and drop another 6 to 10 inches in the mountains (.6-.8 inches SWE) with strong winds and falling temperatures.

Snowpack and Avalanche Discussion:

The Bridger Range:

Storm totals at 5:00 AM in the Bridger Range were 19 inches of snow and 2.4 inches of SWE. The avalanche message today is simple: A lot of heavy snow was rapidly added to a very weak and unstable snowpack. Avalanches are very likely.

This is the largest storm of the year and the first time the snowpack has been put under this much stress. It is failing. Weak faceted snow is unable to hold this new storm snow. Traveling in and underneath avalanche terrain is extremely dangerous. Avalanches were reported running on the ground on the west side of the range yesterday. I saw a large natural avalanche above Fairy Lake Sunday night and expect many, many more. For today in the Bridger Range we have issued an Avalanche Warning which means a HIGH Avalanche Danger exists on all slopes.

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

Lots of heavy, wet snow fell with stiff westerly winds. Faceted snow formed at the surface during last week's clear weather and is now buried. Skiers triggered slides on this layer over the weekend and it will continue to avalanche as more snow is piled on top of it (Sunday's video and photo shows this). Compounding the danger is weak, sugary, faceted snow at the ground. Avalanches breaking in the upper layer may step down to the ground creating large, deadly slides. Storm totals measure 8 to 12 inches, but inches of snow are not important; its total weight is. And the snow weighs a lot: 1.5 - 1.8 inches of SWE. Strong wind gusts to 60 mph have created thick, meaty drifts which further raise the instability.

The Avalanche Danger is rated HIGH on:

• Any wind loaded slope.

• Any slope 35 degrees or steeper.

The Avalanche Danger is rated CONSIDERABLE on all other slopes. This danger rating is very close to our Warning criteria. If snow continues to fall the danger will also increase.

I recommend riding lifts in the ski areas, sticking to groomed trails or staying home. If you do head into the backcountry, make sure your inclinometer is handy. Slopes steeper than 30 degrees are avalanche terrain. Do not travel in or underneath these slopes, no matter how small they are.

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. 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.