February 26 Avalanche Advisory

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, February 26, 2010.

Current Avalanche Danger

Above 6000′ on terrain steeper than 35 degrees the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible.

Below 6000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

At the highest elevations and above tree-line in our mountain ranges, dangerous pockets of unstable snow still exist. Time, warmer weather and very little new snow has settled overall conditions but isolated areas that are very dangerous exist and will remain with us for a few more days. So please remember this: a moderate hazard rating does not mean the danger is gone, just diminished over a broad area. Use this advisory as a starting point. This will give you a good idea of what the potential avalanche problem is and remember we recreate in a dynamic environment where change is constant, over both time and terrain.

Weather and Snowpack Analysis

Mountain weather since Monday has been more of the same (no new snow) with temperatures reaching 45 degrees at Lolo and Lookout passes Tuesday with other SNOTEL locations all reporting temperatures in the high 30’s. Cloud cover moved in and it started snowing early Thursday but we were only able to squeeze a couple of inches of snow from it. Lookout Pass picked up the most with 4 inches in the past 24 hours.

The wind probably did more to improve skiing conditions at 8000 feet as wind speeds have been in the 15-30 mph range for the duration of the week starting out from the NW on Monday and slowly working around the W half of the compass to a strong S-SW flow Tuesday, then back again to a W-NW flow Thursday. Elevations below 7500-8000 feet did not seem to be affected by these strong winds.

We have not received any reports of triggered or natural avalanches since Saturday and all observers reported stronger stability tests but all failures involve the buried surface hoar we’ve been describing for 3 weeks now. On average, it is 25-30cm deep (deeper at higher elevations or near ridge tops on wind loaded slopes) and can be found on all aspects including elevations near the passes. The problem with this particular layer is that it is well protected from the warmer temperatures and will persist as a potential problem whenever we see new snowfall or wind.

It’s easy to find by digging a quick pit no deeper than 2 feet down. It will show up as a thin stripe in the pit wall. Poke your fist and fingers into the pit wall to see the differences in strength. With a thin, weak and highly variable snowpack this season and several close calls last week, you need to become more of an investigator than a robber or you stand a good chance of getting caught by the goods themselves.

Your riding or skiing partners might think you’re some new kind of freak but they will be impressed when the snow pulls out from under one of them and you say “I told you it was weak”!

Weather Forecast and Avalanche Outlook

An upper level ridge is moving through the northern Rockies today allowing a more southerly air flow that will bring very mild temperatures to the area through Saturday. Very little precipitation is expected until sometime next week.

Expect conditions to slowly improve with the moderate temperatures. The next storm cycle will be potentially very dangerous if it comes in quick, warm and with a lot of precipitation. If the clouds break and we have direct sun on the slope, conditions can rapidly become unstable. Get off and out from underneath any steep open slope. Move to a shaded slope or just stick to the groomers on the ski areas.

The past 2 weeks have been edgy in many areas and we’ve been getting some of the best observations and photographs from skiers and riders we’ve seen since we started this web site several years ago. Your observations help us produce a more accurate advisory and may save a life. If you get out and see avalanche activity or want to send us quick snow observations, send us a note at [email protected] or call us at 406-530-9766. 530-9SNO.