January 26 Avalanche Advisory

Good morning! This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for January 26th, 2009. This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but you can expect avalanche conditions to remain similar unless weather conditions change significantly. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Last week’s warmer temperatures followed by this weekend’s quick cold snap have helped further stabilize the more worrisome features we’ve been addressing the past few weeks. With each passing day, it continues to get more difficult to produce failures during our stability testing. If you like sliding on concrete, this is the time for you to get out!

We received good information from backcountry riders in the Southern Bitterroot who indicated stable conditions and faceted snow growth at the surface. As mentioned last week, this feature needs to be considered during the next big storm. We’ve also been receiving reports from locations that were near last week’s inversion transition zone. These locations saw significant surface hoar growth (due to the higher humidity) while the higher (and warmer/drier) elevations were too dry to allow SH development.

As far as the rotten snow at the ground is concerned, we’ve been talking about this all winter and it just isn’t going away anytime soon. The warmer weather helped glue things together now that it’s cold again but those facets at the ground are pretty well insulated and remain a concern on some slopes. Areas that have shallow or thin snow cover are the most susceptible to failure at this level but it takes a lot of force. We were only able to produce failures on pockets of shallow snow (less than 100cm) on East and West aspects.

You can view 2 good examples of this on these YouTube videos:

Video 1

Video 2

Current Avalanche Danger

At all advisory area locations the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low avalanche danger does not mean no avalanche danger. Dangerous avalanche conditions do exist in isolated areas where the snow is thin. These are typically found on West, South and East aspects, in rocky areas or where wind has scoured the snowpack. It takes a lot of force to produce failure of the snowpack in these areas, but it fails to the ground.

Weather Forecast and Avalanche Outlook

Mostly dry and cool weather is expected for the next couple of days. Arctic air will remain in place while high pressure develops over the region. The next best chance for snow appears to be Wednesday during a transition to a Northwesterly flow aloft bringing increasing cloud cover and a bit more Pacific moisture.

Expect avalanche conditions to remain similar until we receive significant snowfall. The weak, sugary, rotten snow that formed during the cold weather in December is still there, you can find it on most aspects between 6000′ and 9000′ and you can never completely trust it. Although we’re saying the avalanche danger is now low to moderate, it’s still possible to rip out a massive slab with the right amount of force in just the right place. So what do you do? Simple! Go one at a time!

If you have any information you’d like to share or have questions about anything related to snow safety, please contact us at [email protected]

The next avalanche advisory will be posted Friday January 30th, 2009.