THIS ADVISORY HAS EXPIRED
ISSUED ON March 6 2014 at 7:00 am.
The Flathead Avalanche Center is issuing a Backcountry Avalanche Warning for the entire advisory area including the Whitefish Range, Swan Range, Flathead Range, and portions of Glacier National Park. Continued snow, rising temperatures and snow levels, and strong winds have created highly unstable conditions. Natural and human triggered avalanches are likely.The avalanche danger is rated HIGH on all slopes in our advisory area. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended and avalanche runout zones should be avoided.
This warning will either be allowed to expire or updated by 7:00 a.m. on Friday, March 7.
Good morning! This is Todd Hannan with the Flathead Avalanche Center avalanche advisory for Thursday, March 6, 2014. This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory will be Saturday, March 8, 2014.
In the past 24 hours we received an additional .9-1.7 inches of snow water equivalent with snowfall amounts ranging from 5-9 inches of heavy snow. Currently temperatures are 30- 36°F and winds range from 5mph up to 25 mph out of the southwest. For today expect light snow showers to taper this morning with renewed intensity late afternoon/early evening. Snow levels should remain fairly high, we could continue to see rain up to 5000 feet today, winds will be out of the southwest 10-25 mph with stronger gusts on the ridge tops.
This is a storm where snow accumulation may not be as impressive as the amount of snow water equivalent (SWE). SWE of new snow is basically the weight added to the existing snowpack, and the mountains picked up a lot! Here is a summary:
Storm Totals: Since Sun. 3/2 at 4:00 a.m.
Shed 7 (John F. Stevens Canyon): 23”
Noisy Basin (Swan Range): 2.9” SWE, 13” snow
Flattop Mt. (Glacier Park): 5.1” SWE, 26” snow
Stahl Pk. (Whitefish Range): 3.9” SWE, 21” snow
Pike Creek (Flathead Range): 3.3” SWE, 23” snow
BNSF avalanche safety reported substantial natural avalanche activity in their program area overnight, with sizes up to 3.5 out of 5 on the destructive scale. The 3.5 on the destructive scale signifies that it is on the high end of the 3 class where an avalanche could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees (Snow, Weather, and Avalanches (3.6.5 Size)).
Avalanche Problem #1
Over the past few days we have seen a substantial amount of weight added to the snowpack. Short lulls in precipitation have not been sufficient to allow for adjustment to the load. Since the onset of the storm on Sunday, temperatures have warmed, piling heavier more dense snow on top of colder lower density snow. In addition to new snow that recently fell, there have been winds capable of transporting snow and loading leeward slopes with an even heavier burden. The snowpack is providing us with obvious signs of instability such as natural avalanche activity, shooting cracks, and collapsing. It is recommended to heed its warning and avoid avalanche terrain and run outs today.
Avalanche Problem #2
Given the relatively high snow levels today and potential for continued rain at high elevations, wet avalanches are a concern. We saw loose, wet avalanche activity Tuesday and more was reported yesterday. The wide scale collapsing we experienced at low elevations on Tuesday demonstrates the potential for wet slab activity to occur. We could also begin to see renewed activity from glide cracks. At low elevations on roads or trails remember that even small avalanche paths and cut banks can produce dangerous avalanches. Avoid steep slopes and terrain traps such as gullies and narrow canyons when surface snow becomes wet, you observe pin wheels, or it is raining on the snow.
Avalanche Problem #3
Persistent slab remains a concern, particularly as we stress them with a new load. The deep persistent slab on the mid-January crust with weak snow adjacent to the crust still poses a threat in many areas. Additionally, there have been several recent observations of layers of weak faceted snow buried 2-3 feet down from the surface. Once initiated, a persistent slab has the ability to propagate long distances, change aspects, and wrap around terrain features. Remain vigilant in assessing slopes for persistent slab instabilities and be aware of the potential for smaller avalanches to step down into these deeper layers and propagate longer distances. Identifying persistent slab is only half of the battle, be thinking of how and in what areas you might be able to trigger them. Continue to avoid areas where triggering these deeper slabs is more likely, such as steep convex rollovers and in areas with shallow snow often found in steep rocky terrain or scoured areas.
For today the avalanche hazard is rated HIGH. Continued precipitation with rising snow levels and temperatures, will cause very unstable conditions. This means that natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended.
Note: Once again, given this persistent slab problem, we need data/information. The accuracy of the avalanche advisory and our understanding of this persistent slab problem becomes much more robust when we have more information. Thus, observations from all of you are extremely valuable to us. Even it is just a simple email saying “Hey, we found good riding in Mountain Range X, and observed no signs of instability or recent avalanches”. This type of information is just as important as observations of avalanches. The observations need not be formal, and can remain anonymous. Don’t’ worry, we won’t give away your secret riding spot either. Call us at 406.261.9873 or email us at email@example.com. Thanks for your help.
Community Avalanche Awareness Night!!! Join the new Friends of the Flathead Avalanche Center (FOFAC) for avalanche discussions followed by an opportunity to socialize with other winter backcountry enthusiasts.
March 6, 2014 (Thursday). 6:30 pm – 8:00 pm program and social afterwards. Moose Lodge, Whitefish. Details here.
New blog post by Ted Steiner about risk assessment in the backcountry here.
See recent snow profiles as well as snow profiles from the entire season here.
Join us March 14, 8:00 p.m. at Penco. We are working with the Flathead Snowmobile Association for the first in a series of motorized specific backcountry safety seminars. Details here.
Check out an interesting new research project that you can participate in about winter backcountry riding/snowmobiling and decision making from the Snow and Avalanche Lab at MSU. Details here.
Observations are extremely valuable to us. If you’ve been out in the backcountry, please drop us a line with your observations at firstname.lastname@example.org or call 406.261.9873. Thanks!
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.