Today...Breezy. Snow likely. Snow accumulation of 2 to 5 inches. Highs 26°F to 32°F. Southwest winds 15 to 20 mph. Chance of snow 70 percent.

Tonight...Breezy...cloudy. Snow likely in the evening...then chance of snow after midnight. Snow accumulation of 2 to 3 inches. Total snow accumulation 4 to 9 inches. Lows 2°F to 8°F. West winds 15 to 20 mph. Chance of snow 70 percent.

Friday...Partly cloudy. Highs 16°F to 22°F. West winds around 15 mph late in the afternoon.

Friday Night...Partly cloudy. Lows 0°F to 6°F. West winds around 15 mph in the evening.

Saturday...Partly cloudy in the morning then becoming mostly cloudy. A 20 percent chance of snow. Highs 18°F to 24°F. Southwest winds around 15 mph in the afternoon.

Saturday Night...Partly cloudy. Lows 5°F to 11°F.

Sunday...Partly cloudy in the morning then becoming mostly cloudy. A 20 percent chance of snow. Highs 25°F to 31°F.

Sunday Night...Partly cloudy with slight chance of snow in the evening...then mostly cloudy with chance of snow after midnight. Lows 13°F to 19°F. Chance of snow 40 percent.

Monday...Mostly cloudy with a 50 percent chance of snow. Highs 25°F to 31°F.

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

Tuesday...Mostly cloudy with a 20 percent chance of snow. Highs 25 to 31.

Tuesday Night...Mostly cloudy with a 30 percent chance of snow. Lows 10°F to 16°F.

Wednesday...Mostly cloudy with a 40 percent chance of snow. Highs 26°F to 32°F.

♦ WINTER STORM ADVISORY ♦

A Winter Storm Advisory remains in effect from 5:00 AM early this morning to 5:00 AM MST Friday.

YELLOWSTONE NATIONAL PARK - INCLUDING THE CITIES OF...LAKE...MAMMOTH...OLD FAITHFUL - 2:22 AM MST THU JAN 26 2012

THE NATIONAL WEATHER SERVICE IN RIVERTON HAS ISSUED A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW...WHICH IS IN EFFECT FROM 5:00 AM EARLY THIS MORNING TO 5:00 AM MST FRIDAY.

* SUMMARY AND TIMING...SNOW WILL BEGIN THIS MORNING AND LAST INTO TONIGHT. THE HEAVIEST SNOW WILL FALL FROM THE LATE MORNING HOURS THROUGH THE EVENING.

* SNOW ACCUMULATIONS...6 TO 12 INCHES IN THE SOUTHWEST PORTIONS OF THE PARK. LESSER AMOUNTS IN THE 3 TO 6 INCH RANGE ARE LIKELY AROUND MAMMOTH.

* WIND AND VISIBILITY...15 TO 25 MPH WITH GUSTS OVER 30 MPH. VISIBILITY WILL BE REDUCED BELOW ONE QUARTER MILE AT TIMES.

* IMPACTS...THOSE WITH OUTDOOR INTERESTS SHOULD BE ALERT TO DETERIORATING WEATHER CONDITIONS AND BE PREPARED FOR POTENTIALLY HAZARDOUS TRAVEL.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY MEANS THAT PERIODS OF SNOW AND BLOWING SNOW WILL CAUSE TRAVEL DIFFICULTIES. BE PREPARED FOR SLIPPERY ROADS AND LIMITED VISIBILITIES...AND USE CAUTION WHILE DRIVING.

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

Mountain Weather

In the last 24 hours, 1 to 2 inches of snow fell near Big Sky and West Yellowstone and 3 to 4 inches fell near Cooke City. However, strong winds dominated yesterday's weather averaging 30-40 mph and gusting 50-70 mph from the West. This morning westerly winds eased and were blowing 15-20 mph, gusting 30-40 mph. Temperatures were in the high teens and low 20s Fahrenheit. Today temperatures will rise into the upper 20s Fahrenheit, and winds may calm a bit more. More snow will fall with 1 to 2 inches near Big Sky and Bozeman and 3 to 4 inches further south.

Snowpack and Avalanche Discussion:

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

The snowpack in the southern mountains between West Yellowstone and the Taylor Fork drainage is not complicated. The bottom half is all weak facets and the upper half is new snow that has fallen in the last 10 days. This layering will be evident when you step off your sled or out of your skis and sink to the ground. On Tuesday near Lionhead, my riding partners and I dug snowpits and did stability tests but these weren't necessary to assess stability. We knew the snowpack was weak because our track would trench through the snowpack and bounce off buried rocks and trees. We knew the snowpack was unstable because we saw countless avalanches both new and old. A few slopes had not produced avalanches, and we treated these slopes like a loaded gun. On the same day nearby, Karl also found natural avalanche activity, a snowpack with a weak base, and unstable conditions.

The mountains near Cooke City received almost double the precipitation of other areas and many avalanches have occurred in this area. Yesterday at Lulu Pass, very strong winds made Doug feel like he was on Denali. On a south facing slope on Scotch Bonnet Mountain he found weak facets on an ice crust (video). This same layer produced a massive avalanche in the SE bowl on Scotch Bonnet and in several South facing chutes closer to Lulu Pass. Two weeks ago, I found a similar layer on S aspects near Sheep Creek. N aspects do not have this layer, but some have weak depth hoar that will easily break while others have relatively strong snow.

Very strong winds have readily transported snow and formed hard wind slabs. Doug said that wind loading was occurring at seemingly random spots. A few natural avalanches are possible, but conditions are ripe for more human triggered avalanches and for today the Avalanche Danger is CONSIDERABLE.

The Bridger, northern Madison and northern Gallatin Ranges:

The snowpack near Big Sky and Bozeman also contains weak facets. In some places like Hyalite Canyon, these facets have not been problem this season, and near Big Sky in Bear Basin, they seem to be gaining some strength. In the Bridger Range these facets remain very weak. It is worth digging to the ground and assessing these facets. However, the primary concern in these areas is wind loading. Triggering a fresh wind slab should be pretty easy today. Warm temperatures may have helped some wind slabs bond to the underlying snow, but don't trust them. For this reason, the Avalanche Danger is rated CONSIDERABLE on all wind loaded slopes steeper than 35 degrees. Other 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. 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.