Today...Patchy fog early in the morning. Partly cloudy with chance of snow in the morning...then cloudy with snow likely in the afternoon. Snow accumulation up to 1 inch. Highs 27°F to 33°F. Chance of snow 60 percent.

Tonight...Cloudy with a 30 percent chance of snow. Lows 7°F to 13°F.

Tuesday...Breezy. Mostly cloudy. Chance of snow in the afternoon. Highs 24°F to 30°F. Southwest winds 15 to 20 mph in the afternoon. Chance of snow 40 percent.

Tuesday Night...Breezy. Cloudy with a 50 percent chance of snow. Lows 10°F to 16°F. Southwest winds 15 to 25 mph.

Wednesday...Breezy. Mostly cloudy with a 30 percent chance of snow. Highs 30°F to 36°F. Southwest winds 15 to 20 mph.

Wednesday Night...Mostly cloudy with a 20 percent chance of snow. Lows 16°F to 22°F.

Thursday...Mostly cloudy. Chance of snow in the morning...then chance of snow and rain in the afternoon. Highs 35°F to 41°F. Chance of precipitation 40 percent.

Thursday Night...Snow likely. Moderate snow accumulations. Lows 15°F to 21°F. Chance of snow 60 percent.

Friday...Mostly cloudy with a 40 percent chance of snow. Highs 25°F to 31°F.

Friday Night...Colder. Partly cloudy with a 20 percent chance of snow. Lows 8°F to 14°F.

Saturday...Partly cloudy in the morning then becoming mostly cloudy. A 20 percent chance of snow. Highs 28°F to 34°F.

Saturday Night...Mostly cloudy with a 40 percent chance of snow. Lows 13°F to 19°F.

Sunday...Mostly cloudy with a 30 percent chance of snow. Highs 28°F to 34°F.

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Mountain Weather

Since yesterday morning 3 to 4 inches of snow has fallen in the Bridger Range, while a trace to 2 inches has fallen elsewhere. Mountain temperatures are ranging from 5 degrees Fahrenheit in Cooke City to the low teens in most other locations. Winds are fairly calm, blowing out of the Westsouthwest at 5 to 15 mph, with the exception of the Ridge at Bridger Bowl where they are blowing out of the Southsoutheast at 5 to 10 mph. Today, temperatures will warm into the low 30's Fahrenheit under partly cloudy skies and winds will stay light out of Westsouthwest. An increasing chance of snow will arrive tomorrow afternoon.

Snowpack and Avalanche Discussion:

The mountains around Cooke City and the Washburn Range:

Cooke City is in a zone of its own, receiving more than two feet of new snow over the past five days. The latest storm to impact the area deposited more than 18 inches of new snow in a 24 hour period. An observer in the area reported multiple point release slides as well as a few natural slab avalanches in the upper elevations. Fortunately the snowpack in this area lacks a widespread weak layer which is helping to keep avalanche activity to a minimum.

The primary avalanche concern today will be wind loaded slopes, mainly in upper elevation terrain and along ridgelines. A secondary avalanche concern is terrain located below large cornices. Additional loading on cornices has occurred with the recent new snow pushing them closer to failure. Cornices have the ability to break farther back then one might expect and can act as triggers for larger slides once released. Avoiding slopes under overhanging cornices and giving them a wide berth near the ridgelines is a smart idea.

Today, all wind loaded slopes have a CONSIDERABLE Avalanche Danger. Slopes that have not received a wind load have a MODERATE Avalanche Danger.

An additional threat will be wet loose avalanches on slopes heavily affected by the sun. If the sun appears and temperatures warm, wet loose avalanches will be possible on steep, rocky slopes where the surface snow is heavy and wet.

The Bridger, Madison and Gallatin Ranges, and the Lionhead area near West Yellowstone:

Yesterday, Doug and I investigated a human triggered avalanche in the southern Madison Range. The slide was triggered from a cornice drop by a pair of skiers skinning up the ridge (the first report we received was that this slide was remotely triggered, but we later found out it was triggered by a cornice drop). This avalanche broke 2 to 5 feet deep, propagated 150 feet across and occurred on a Southeast facing slope around 9,000 feet. A heavy wind load sitting over a thin layer of small grained facets capped by a .8 inch ice crust was the culprit for this event. The slide was confined to a wind loaded pocket and did not propagate into non-wind loaded terrain.

Although we are not finding buried facets to be a widespread problem, this latest slide is a poignant reminder that lingering instabilities still exist. Looking at the character of this slide, I recognized similarities to both the human triggered slide that Doug investigated near Cooke City a few weeks ago and the slide that resulted in a fatality in the Bridger Range last month. The common thread that ties these slides together is a heavy wind load sitting over a weaker - lower density layer. Many times hard wind slabs are difficult to trigger, but once initiated, they often result in large devastating slides.

Recognizing and avoiding large wind whales and slopes directly under cornices will be the best way to stay out of trouble. Obvious clues such as cracking and collapsing and recent avalanche activity is bull's eye data the snowpack is unstable.

Today, human triggered avalanches are possible on wind loaded slopes which have a MODERATE Avalanche Danger. Slopes that have not received a wind load have a LOW Avalanche Danger.

PHOTOS, SNOWPITS, VIDEO and SURVEY RESULTS

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. The results from our survey are posted online. Thanks to all who participated. You can check out the results at http://bit.ly/fpLuSi.

In response to our survey we added a new page to the website with images of our snowpit profiles. This page is under the Resources/Other Info tab at http://fsavalanche.org/Encyclopedia/snowpit.htm

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