Yellowstone Seven Day Forecast on 14 January 2011 by the NWS Riverton, WY

Rest Of Today...Breezy. Snow late in the morning...then snow likely in the afternoon. New snow accumulation around 1 inch. Highs 26°F to 32°F. Southwest winds 15 to 20 mph. Chance of snow 90 percent.

Tonight...Breezy. Snow likely. Snow accumulation of 1 to 2 inches. Lows 18°F to 24°F. Southwest winds 15 to 20 mph. Chance of snow 70 percent.

Saturday...Breezy. Snow likely in the morning...then snow in the afternoon. Snow accumulation of 2 to 3 inches. Highs 26°F to 32°F. Southwest winds 15 to 20 mph. Chance of snow 90 percent.

Saturday Night...Breezy. Snow likely. Snow accumulation of 2 to 3 inches. Lows 18°F to 24°F. Southwest winds 15 to 20 mph. Chance of snow 70 percent.

Sunday...Breezy. Snow likely. Snow accumulation of 3 to 5 inches. Highs 29°F to 35°F. Southwest winds 15 to 20 mph. Chance of snow 70 percent.

Sunday Night...Snow likely. Moderate snow accumulations. Lows 21°F to 27°F. Chance of snow 70 percent.

Monday / Martin Luther King Jr Day...Snow likely. Light snow accumulations. Highs 27°F to 33°F. Chance of snow 60 percent.

Monday Night...Cloudy with a 50 percent chance of snow. Lows 15°F to 21°F.

Tuesday...Cloudy with a 50 percent chance of snow. Highs 25°F to 31°F.

Tuesday Night...Cloudy with a 50 percent chance of snow. Lows 13°F to 19°F.

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

Wednesday Night...Colder. Mostly cloudy with a 40 percent chance of snow. Lows 6°F to 12°F.

Thursday...Mostly cloudy with a 30 percent chance of snow. Highs 23°F to 29°F.

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

Avalanche Information - from the Gallatin National Forest Avalanche Center this report is by Mark Staples

Mountain Weather:

Since yesterday the mountains near Cooke City and West Yellowstone received 6-8 inches of snow, the mountains near Big Sky received a trace to 1 inch, and the mountains near Bozeman remained dry. Little has changed in the weather with warm and windy conditions which should continue today. Temperatures this morning were in the mid 20s Fahrenheit except near Cooke City and West Yellowstone where they were in the high teens Fahrenheit. Winds were blowing 15-30 mph from the Westnorthwest with gusts near Bozeman in the 40s. Today temperatures should approach 30 degrees Fahrenheit, and winds shouldn't change much. By tomorrow morning only a trace to 1 inch of snow should fall, but more is coming this weekend.

Snowpack and Avalanche Discussion:

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

A skier yesterday in the southern Madison Range found faceted snow formed at the surface during very cold temperatures early this week. With new snow on top of this weak layer, he easily ski cut 4-12 inch soft slabs. Deeper in the snowpack, no widespread, persistent weak layers exist. Isolated areas may contain deeper instabilities, but these are rare. This means what you see in your snowpit or test slopes will be very similar to what you will find on bigger slopes nearby. With new snow and continued strong westerly winds, soft slab avalanches are the primary concern especially on slopes with wind drifted snow.

For today with easily triggered wind slabs, the Avalanche Danger is rated CONSIDERABLE on wind loaded slopes steeper than 35 degrees and MODERATE on all others.

The northern Madison Range:

Personally, I'd drive right past the Big Sky area and head further south where stability assessments area easier. Riding in the mountains near Big Sky requires more work to safely play in avalanche terrain. Fresh wind slabs are the main issue as they are in the rest of the advisory area, and yesterday Gallatin Snow Rangers noted substantial drifting on Buck Ridge even at lower elevations. What makes stability assessments more difficult is a layer of buried surface hoar about 2-3 feet deep. This layer has gained some strength but at different rates on different slopes. Also, it doesn't exist everywhere which means you may not find it on one slope, but may find it on another.

Today heightened avalanche conditions exist where the surface hoar is present and where recent wind drifts exist and the Avalanche Danger is rated MODERATE.

The Bridger Range and northern Gallatin Range:

Sadly, the mountains near Bozeman have received stronger winds than other areas and less snow. The main areas of concern exist near ridgelines where the snowpack is thin. Because temperatures at the bottom of the snowpack are always 32 degrees F, recent periods of very cold weather have created steep temperature gradients where the snowpack is thin. Steep temperature gradients create weak, faceted snow. Recent strong winds have capped this weak snow with stiff wind slabs and given us a good recipe for an avalanche. Without the stress of new snow, these wind slabs shouldn't be very sensitive, but they make human triggered avalanches possible.

For today, the Avalanche Danger is rated MODERATE on all wind loaded slopes, MODERATE on all slopes steeper than 35 degrees, and LOW on less steep slopes without a wind load.

Information provided by Doug Chabot, Mark Staples, and Eric Knoff from the Gallatin National Forest Avalanche Center.

For detailed Avalanche Terms utilized here, please see the Avalanche Glossary.

~ Mammoth Weather Forecast ~