March 5 Avalanche Advisory

Hello! This is Steve Karkanen with backcountry avalanche information from the West Central Montana Avalanche Center for Friday, March 5, 2010.

Current Avalanche Danger

Above 6000 feet 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. We are rapidly losing snow at the lower elevations and 5000 feet is the transition zone from no snow to some snow depending on aspect.

Weekend temperatures are expected to be above freezing even with cloud cover. On slopes exposed to the sun the wet snow avalanche danger will quickly rise to CONSIDERABLE. Human triggered avalanches are probable, natural avalanches are possible. Roller-balls and small point release avalanches are good indicators of an increasingly unstable condition. If you see these indicators or begin punching through the snow to your knees you need to move to a more shaded aspect. Be mindful of what you are exposed to from above.

Weather and Snowpack Analysis

We have been through an extended period of near record breaking warm temperatures with a short cool down Wednesday with minimal precipitation. The weather forecast looks like we go back to warm weather with no precipitation at least through the weekend. These unseasonal warm temperatures have done a lot to wreck the skiing, make the southern exposures nearly isothermal and send all but the die-hard back to town for grassy sports, riding bikes or fishing. A lot of choices these days but come on, there’s nothing better than being on the snow when the sun is out, the snow is corn and the view outstanding. And if you know where to look and time it right, the backcountry skiing and riding is still pretty good.

But you have to be careful as we continue to find the buried surface hoar layer we’ve been describing for the past month to be sensitive in our stability evaluations. This is a widespread condition I think now mostly confined to the more sheltered NW to NE aspects or pockets heavily shaded from the sun. This video gives a good idea of how persistent the problem has been now. Certainly strengthening with the warmer temperatures but still a potential problem worth looking for especially at the higher elevations (7500 feet +).

httpv://www.youtube.com/watch?v=kNXwthEH3IU

The sun exposed aspects have been warmed to the point where in many areas our observers are finding the snow to be rotten to the ground. With mountain temperatures in the 40’s, the southern aspects will be prone to slide in the afternoon hours. They might look OK and are probably just fine in the morning, but during the peak of direct sun or when you start punching through last nights crust, your best course of action is to move to a shaded slope. But don’t forget about the buried surface hoar layer we just showed you!

Weather Forecast and Avalanche Outlook

The National Weather Service Office in Missoula is forecasting the weak upper level low pressure system currently over us with isolated snow showers mostly in the southern Bitterroot to move to the east this weekend leaving mostly dry conditions. Saturday and Sunday are expected to be very nice with some clouds lingering over the mountains. The next chance for any appreciable precipitation is early next week.

Expect wet snow avalanche danger to increase during warm afternoons. The stability on northerly aspects will continue to strengthen with the moderate temperatures but don’t completely trust anything until you have proven the slope is stable. The variability of our snowpack in Western Montana has been a nagging problem this year. The only slopes you can be 100% sure are safe are those brown grassy hillsides up to the snowline. Above that, pay attention!

If you have not taken the survey, this is your last chance. We plan to take it down and tally the results after Monday March 8. So please take the survey and register for a chance to win a Tracker transceiver, Voille shovel, or a missoulaavalanche tee shirt.

With the current early spring conditions, we plan to issue the final Monday advisory on March 8. This is dependent on weather conditions and we will issue early week advisories as conditions change. We plan to continue with Friday advisories to March 26.