Dec 17, 2013 @ 6:38 am

December 17, 2013 Avalanche Advisory

The avalanche danger in the west central Montana backcountry is MODERATE. It is possible to trigger an avalanche on slopes above 7000 feet that are wind-loaded and 30 degrees and steeper. On other terrain in the advisory area the avalanche danger is LOW. Low avalanche danger does not mean “no avalanche danger”; if you are on slopes that are 35 degrees and steeper there is always some chance the snow could slide.

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday December 17, 2013. This danger rating expires at midnight tonight. (Dec. 17, 2013).

Weather and Snowpack Analysis

This morning, mountain temperatures are in the low twenties. West and southwest winds above 7000 feet are blowing at 20+ mph and gusting into the 30’s. There is no new snow to report.

Mountain winds blew hard over the weekend and created wind slabs at higher elevations. We received a report of a skier-triggered wind slab on Sunday near St. Mary’s Peak. The slide occurred on an east aspect at 8200 feet in elevation. The crown of the avalanche varied from 6 to 12 inches. (photo) (video) The skier who triggered the slide was able to self-arrest and escape. The report indicated the skiers felt like they didn’t pay enough attention to the high winds and wind-scoured ridge tops. I quote from their report “don’t forget to mention really high winds. I held on with all my strength for awhile to keep from being blown off the ridge. Been hang gliding for years so I know what wind looks like and that was fairly radical. May have affected my decision to get off of the ridge as fast as possible. Then skied wind scoured cement for the next 1200′ vertical or so. Didn’t recognize the point where it changed from wind scoured to wind loaded and it almost cost us big time. The most learning I’ve packed into 6 seconds for awhile”.

The willingness of folks to send us reports like the one above can’t be over-appreciated. These candid notes and comments are great learning tools for us.

We haven’t received much snow since last week and the temperatures have been seasonably warm. Snotel sites indicate overall settlement of the snowpack. The above mentioned avalanche shows you can never discount the wind, no matter what everything else (including strong snow pit test scores) is telling you.

One other concern in the snowpack are facets near the bottom that were formed during the very cold weather 9 days ago. Yesterday, Steve and I found those facets near the ground, just above 6000’ near Lolo Pass. We had a report from an avid local skier who observed the same thing at higher elevations in the Bitterroots. Those facets failed in one of our snow pit tests yesterday. In this video the snow doesn’t fail but it shows the facets near the ground. I would expect to find this weakness on the very cold, north aspects; it is something to keep in mind if we get a big snow in the near future.

Weather Forecast and Avalanche Outlook

A mild air mass is expected to remain over the region through today with temperatures 10 to 15 degrees above normal. A weather system will then move southward over the northern Rockies Wednesday and Thursday with a colder air mass. This event may produce significant mountain snow.

Gear and Practice

Although many early-season “keeners” have been hunting powder (instead of deer & elk) for a while; a lot of  folks are just getting started. Our beacon parks are up and ready at Lost Trail Pass, Lolo Pass and Snowbowl. Think about putting together your shovels and probes and checking them over; perhaps apply a bit of silicone to the joints. It’s a good idea to put fresh batteries in your transceivers and check their functionality. If you have Avalungs or airbags, check to make sure everything is operational. And, consider practicing with your rescue gear.

If you would like to report on avalanche or snow conditions use our public observations form or send us a note at [email protected] .

Ski and ride safe!

I will issue the next avalanche advisory Friday, December 20.


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 the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.