Yellowstone Seven Day Forecast on 05 January 2011 by the NWS Riverton, WY

Today: Breezy. Snow likely. Snow accumulation around 1 inch. Total snow accumulation 1 to 2 inches. Highs 17°F to 23°F. Southwest winds 15 to 20 mph. Chance of snow 70 percent. Lowest wind chill readings -10°F to -20°F in the morning.

Tonight: Cloudy with a 50 percent chance of snow. Lows 7°F to 13°F. Southwest winds around 15 mph.

Thursday: Cloudy with a 50 percent chance of snow. Highs 23°F to 29°F. Southwest winds around 15 mph early in the morning.

Thursday Night: Mostly cloudy with a 40 percent chance of snow. Patchy fog after midnight. Lows 11°F to 17°F.

Friday: Mostly cloudy. Patchy fog in the morning. Chance of snow in the morning...then slight chance of snow showers in the afternoon. Highs 25°F to 31°F. Chance of snow 30 percent.

Friday Night: Cloudy with a 50 percent chance of snow. Lows 11°F to 17°F.

Saturday: Snow likely. Moderate snow accumulations. Highs 21°F to 27°F. Chance of snow 70 percent.

Saturday Night: Colder. Mostly cloudy with a 40 percent chance of snow. Lows -4°F to 4°F.

Sunday: Colder. Mostly cloudy with a 30 percent chance of snow. Highs 7°F to 13°F.

Sunday Night: Colder. Mostly cloudy with a 20 percent chance of snow. Lows -4°F to -14°F.

Monday: Mostly cloudy with a 20 percent chance of snow. Highs 5°F to 11°F.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. A 20 percent chance of snow. Lows -2°F to -8°F.

Tuesday: Partly cloudy with a 20 percent chance of snow. Highs 7°F to 13°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 Doug Chabot

Mountain Weather:

At 6:00 AM the Yellowstone Club is showing ten inches of new snow. All the other ski areas got six inches with other sites also reading 3-6 inches. Temperatures warmed into the teens as wind speeds increased out of the southwest averaging 20-30 mph with gusts reaching 40-50 mph. Under mostly cloudy skies mountain temperatures will climb into the low 20s today with strong southwest winds. More flurries this morning and again later tonight will drop an additional two to four inches.

Snowpack and Avalanche Discussion:

The northern Madison Range:

Up to ten inches of light, 5% powder, fell in the mountains around Big Sky last night. Southwest winds are blowing 20-30 mph which is moving the new snow into soft slabs near the ridgelines. The northern Madison Range has a layer of buried surface hoar 12-18 inches deep on many slopes and this new snow will keep the avalanche danger heightened. We received three observations from these mountains yesterday: one wrote about collapsing and surface hoar propagating fractures in a snowpit on Yellow Mountain; another had compression tests failing with light taps near Beehive Peak while a third found stable snow and no surface hoar on west-facing slopes in Beehive Basin. Divergent reports like these can occur as the weak layer begins to strengthen and loses its consistency throughout a region. Although this ultimately makes finding the instability trickier, it's a trend we like to see. Given the new snow, wind and buried weak layer, the Avalanche Danger today is rated CONSIDERABLE on all wind-loaded terrain. On slopes not affected by the wind the Danger remains MODERATE.

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

Three to six inches of light density powder has fallen at most SNOTEL sites which are also measuring .2-.4 inches of Snow Water Equivalent (SWE). The new snow will be drifted into soft slabs on the ridgelines and easily triggered, but not step down into older snow. The avalanche danger will be spiked only on wind-loaded terrain since most ranges have a strong snowpack. Mount Ellis, Teepee Creek, Lionhead, and Cooke City have layers that are bonding well together. A lone blip in this story was reported by a skier in Taylor Fork in the southern Madison Range yesterday. He noted collapsing and found surface hoar buried a foot deep. On one hand, this is good news because we know the instability is not widespread. On the other hand, it shows that we still need to be on the lookout for buried weak layers. Luckily it's only 12 inches deep and we can find it with hand pits.

Today, it's likely a person could trigger a slide on wind-loaded slopes, so I'm rating the Avalanche Danger CONSIDERABLE on this terrain. For slopes without wind deposits, the Avalanche Danger is rated MODERATE on all slopes steeper than 35 degrees while lesser angled slopes have a LOW Danger.

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

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

Gallatin National Forest Avalanche Center ~ Mammoth Weather Forecast