Avalanche Information - from the Gallatin National Forest Avalanche Center

Mountain Weather:

Under cloudy skies a trace of snow has fallen this morning. In the northern mountains temperatures are in the single digits while around West Yellowstone and Cooke City the temperatures are 0°F to -10°F. Winds are from the west to northwest averaging 15-20 mph with gusts in the 30s. Today will remain cloudy with temperatures warming into the teens as northwest winds blow 20-30 mph. Small weather disturbances will bring flurries, but accumulations will be less than an inch by tomorrow morning.

Snowpack and Avalanche Discussion:

The northern Madison Range:

Slopes continue to show instability in the mountains around Big Sky. On Friday, snowmobilers triggered a slide in the first Yellowmule on Buck Ridge. That same day a skier on Yellow Mountain got collapsing as he approached a steep slope. In the last 48 hours strong westerly winds blew snow into slabs that broke with ski cuts; all the ski patrols reported this. Yesterday, a skier saw evidence of a few natural slides on wind-loaded slopes near Mount Wilson and Dudley Peak breaking 12-18 inches deep. He got collapsing/whumphs as he skied, had cornices crack under his feet and got the buried surface hoar to break clean in all four of his snowpits.

Winds are still blowing and loading slopes. Last week’s storm left plenty of snow to move which will keep the danger elevated. On slopes with a buried surface hoar layer avalanches will break into deeper snow. New snow last week, continued winds, recent avalanche activity and a persistent weak layer make heading into the backcountry serious business. For today, the avalanche danger is rated CONSIDERABLE on all slopes.

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

We received many observations in the last two days from riders and skiers who headed out in the zero degree temperatures. The reports had a common thread: wind-loaded slopes were sensitive to human triggers. The Bridger Bowl Ski Patrol found wind pillows 4-16 inches deep avalanching from a simple jump. On Electric Peak in the southern Gallatin Range, a skier wrote about lots of new snow and thin wind drifts cracking as he toured. Besides the recent wind slabs, the snowpack is generally strong with good stability. Last Wednesday we found solid snow near Hebgen Lake and also on Mount Ellis two days ago. There are isolated slopes with weak snow: some spotty surface hoar buried near Flathead Pass and down south in Bacon Rind. A few stability tests a couple feet deep will tell you if there are layers to be concerned with. There’s no need to dig to the ground since the weak snow is found in the upper pack. For today, the avalanche danger is rated CONSIDERABLE on all wind-loaded slopes steeper than 35 degrees and MODERATE on all others.

Gallatin National Forest Avalanche Center ~ Mammoth Weather Forecast

Yellowstone Seven Day Forecast on 02 January 2011 by the NWS Riverton, WY

Today: Breezy. Cloudy with a 40 percent chance of snow. Highs 8°F to 14°F. Southwest winds 15 to 20 mph. Lowest wind chill readings -32°F to -42°F in the morning.

Tonight: Breezy. Cloudy with a 40 percent chance of snow. Lows -3°F to -9°F. West winds 15 to 20 mph.

Monday: Cloudy with a 20 percent chance of snow in the morning... Then partly cloudy in the afternoon. Highs 13°F to 19°F. West winds around 15 mph early in the morning becoming west around 15 mph late in the afternoon. Lowest wind chill readings -18°F to -28°F in the morning.

Monday Night: Partly cloudy. Lows -7°F to 1°F. Southwest winds around 15 mph.

Tuesday: Mostly cloudy with a 20 percent chance of snow. Highs 14°F to 20°F. Southwest winds around 15 mph in the afternoon. Lowest wind chill readings -14°F to -24°F in the morning.

Tuesday Night: Mostly cloudy with a 20 percent chance of snow. Lows 0°F to 6°F.

Wednesday: Mostly cloudy with a 20 percent chance of snow showers. Highs 18°F to 24°F. Lowest wind chill readings -12°F to -22°F in the morning.

Wednesday Night: Mostly cloudy with a 20 percent chance of snow showers. Lows 7°F to 13°F.

Thursday: Partly cloudy with a 20 percent chance of snow showers. Highs 24°F to 30°F.

Thursday Night: Partly cloudy with a 20 percent chance of snow showers. Lows 9°F to 15°F.

Friday: Partly cloudy with a 20 percent chance of snow showers. Highs 25°F to 31°F.

Friday Night: Partly cloudy with a 20 percent chance of snow showers. Lows 11°F to 17°F.

Saturday: Partly cloudy with a 40 percent chance of snow showers. Highs 24°F to 30°F.

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