Today: Mostly sunny, with a high near 23°F and a low around 4°F. Wind chill values as low as -10°F. North northwest wind between 6 and 8 mph.

Saturday: Sunny, with a high near 29°F and a low around 5°F. Wind chill values as low as -5°F. West southwest wind around 6 mph.

Sunday: Partly sunny, with a high near 28°F and a low around 3°F. Southwest wind around 8 mph.

Monday: Mostly sunny, with a high near 24°F and a low around -3°F. North northeast wind between 3 and 5 mph.

Tuesday: Mostly sunny, with a high near 23°F and a low around 4°F.

Wednesday: A slight chance of snow. Partly sunny, with a high near 20°F and a low around 1°F.

Thursday: A slight chance of snow. Partly sunny, with a high near 15°F.

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

Mountain Weather

Yesterday another 2 to 3 inches of snow fell in most areas except the southern Madison Range and the mountains near West Yellowstone which only got a trace. This morning temperatures were in the teens Fahrenheit and ridgetop winds were blowing 10-20 mph from the West-northwest. In the Bridger Range ridgetop winds were blowing 35-40 mph. Today will have sunshine and temperatures in the mid to high 20s Fahrenheit with little change in the winds. The next chance for snow may be Sunday evening.

Curious why La Nina hasn't brought more snow to Southwest Montana? Read a brief explanation from the National Weather Service office in Missoula here.

Snowpack and Avalanche Discussion:

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

One of the biggest factors affecting the avalanche danger is significant snowfall. Without much stress from new snow, there have been few avalanches. Although the snowpack is weak in most areas, it is generally stable because it has little stress. This situation will change if or when a big storm arrives, but for now the waiting game continues.

Weak layer #1: Snow in October provided beautiful images of fall with snow capped mountains in the background, but this snow has become a layer of weak, faceted crystals called depth hoar lying at the bottom of the snowpack. Avalanches in late November and early December occurred on this layer. Yesterday, my partners and I toured into the Flanders drainage of Hyalite Canyon. Along the way we dug multiple snowpits. In some places where the snow was deepest, this layer was less obvious. In many other places this layer was very obvious and very weak.

Weak layer #2: Recent dry weather created strong temperature gradients at the snow surface. This means the upper few inches of snow experienced big temperature differences which metamorphosed (changed) the old, broken snowflakes into small faceted crystals called near-surface facets. Additionally, many areas have a layer of surface hoar (photo) on top of these facets. Wednesday's snow covered and preserved both these layers. Until more snow falls, these layers are not much of an avalanche hazard.

The current situation: Some slopes have a snowpack more than 2 feet deep with depth hoar at the bottom, a slab in the middle, and more facets on top. Other slopes have a snowpack less than 2 feet deep with depth hoar at the bottom, facets in the middle, and more facets on top. Avalanches require a slab resting on a weak layer. For this reason, slopes with more than 2 feet of snow and any wind deposited snow have a MODERATE Avalanche Danger. Slopes with less than 2 feet of snow and no wind loading have a LOW 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.

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.

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.