Special Avalanche Advisory – 2/17/2014

Issued: February 17, 2014, 7:00 a.m.
Expires: 11:59 p.m. of issue date

Good morning! This is Seth Carbonari with the Flathead Avalanche Center avalanche advisory for Monday, February 17, 2014. This advisory applies only to backcountry areas outside established ski area boundaries. The next scheduled advisory will be Wednesday, February 19, 2014.


MOUNTAIN WEATHER

WeatherGraphicVery little in the way of new precipitation arrived on Sunday.  Weather stations are reporting no new precipitation, temperatures have cooled a bit to the teens to 20’s and some moderate SW winds at elevation with gusts up to 65mph (remote weather stations).  The Flattop SNOTEL Site is the exception and is showing 6 inches of new snow and .9 inches of snow water equivalent in the past 24 hours. The National Weather Service out of Missoula is forecasting the possibility of up to 10 to 15 inches of new snow at higher elevations today and 5 to 8 inches at mid elevations with temperatures remaining in the upper 20’s and moderate WSW winds.

 


RECENT OBSERVATIONS

RecentObservationsGraphicSunday, we were in the Canyon Creek drainage investigating the reported avalanche from Saturday (see preliminary information). We found a melt freeze crust 10 to 18 inches from the surface and of varying hardness. On top of that crust layer we found a weak layer of small facets.  Substantial active wind loading occurred Saturday night through Sunday. We experienced one collapse in the snow pack while traveling along the ridge to the northeast of Canyon Creek. Stability testing revealed unstable results from the weak (faceted) layer above the melt freeze crust.  Extended Column Tests on a southeast slope around 5850 feet produced propagation of quality 1 with easy force.

BNSF avalanche safety reported  a natural avalanche near Shed 7 that was large enough to bury, injure or kill a person (photo1, photo2).

Sunday, we received numerous reports of instability and avalanche activity. Snowmobilers in the Skyland area near Marias Pass reported remotely triggering an avalanche on a north aspect.  Skiers and snowmobilers in the Canyon Creek drainage over the weekend reported a number of human triggered avalanches on southerly facing aspects.  We expect the avalanches reported in Canyon Creek to be running on the same melt freeze crust we encountered.  It is important to note that, not only are we encountering natural avalanches and human triggered avalanches, but we are getting reports of remotely triggered avalanches.  We also received additional reports of natural activity and instability encountered on Saturday in Essex Creek in the Flathead Range.

 Thanks to everyone who sent in observations. They are great and very valuable!

Avalanche on Skookoleel Peak. 2/15/2014.

Avalanche on Skookoleel Peak. 2/15/2014. Photo: Roehner.

Remotely triggered slide about 150 ft. wide and up to 18 inches deep. Whitefish Range. 2/15/2014. Photo: Roehner

Remotely triggered slide about 150 ft. wide and up to 18 inches deep. Whitefish Range. 2/15/2014. Photo: Roehner

Crown of natural avalanche (Class 2) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety  o Approximate crown width: 100 m.  o Approximate crown depth: 60 cm.  o Starting Zone Elevation: 6000 feet.  o Terminus Elevation: 4400 feet  o Starting Zone Aspect: South (135 degrees)

Crown of natural avalanche (Class 2) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety

 

Debris of natural avalanche (Class 2.5) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety.  o Approximate crown width: 100 m.  o Approximate crown depth: 60 cm.  o Starting Zone Elevation: 6000 feet.  o Terminus Elevation: 4400 feet  o Starting Zone Aspect: South (135 degrees)

Debris of natural avalanche (Class 2.5) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety.

Crown of natural avalanche (Class 2.5) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety o Approximate crown width: 30 m.  o Approximate crown depth: 60 cm.  o Starting Zone Elevation: 6000 feet.  o Terminus Elevation: 5000 feet  o Starting Zone Aspect: South (180 degrees)

Crown of natural avalanche (Class 2.5) in John F. Stevens Canyon, Lewis Range, Glacier National Park. 2/16/2014. Photo: BNSF Avalanche Safety

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

SNOWPACK DISCUSSION

Avalanche Problem #1

Storm SnowThe last week has produced a substantial amount of precipitation accompanied by moderate, strong, and at times extreme winds, depositing snow on a variety of weak snow surfaces. With the addition of fluctuating snow/freezing levels, dangerous avalanche conditions developed. Natural and human caused avalanche activity continue to be reported.  Recent storm and wind slabs that have not had time to gain strength are still waiting for added stress to tip the scale and more snow is in the forecast.  Given the forecast for continuing snow and snow transporting winds adding stress to already sensitive storm slabs, it would be wise to continue to avoid wind loaded terrain, steep slopes, and convex rollovers. Keep in mind that wind loaded terrain is not confined to ridge tops. Be aware of cross loaded features at mid elevations such as gulley walls, spur ridges, and rock bands.

 


Avalanche Problem #2

Persistent SlabLayers of weak snow (facets) still exist deeper in the snowpack. The reactivity of these layers has been variable across the advisory area, however the potential for a storm slab or wind slab avalanche to step down to these layers still exists. In areas of shallow snow a layer of weak snow also exists near the ground. It is important to dig and assess each slope for deeper weak layers before riding or skiing it as persistent slabs can be tricky and difficult to assess.

 

 

 


BOTTOM LINE

For today the avalanche hazard is rated as HIGH throughout the advisory area. This means that human triggered avalanches are very likely and natural avalanches are likely . Continue to pay close attention to changing conditions and be prepared to alter plans if conditions warrant. Travel in avalanche terrain is not recommended. 

Note: We are in a period of tricky and dangerous avalanche conditions. Very cautious backcountry travel is warranted. Since February 8, avalanches have killed six people and seriously injured three in the western United States in five separate incidents.

High 

Note: Thank you to all of those who have submitted observations!  They have been extremely helpful during this time of heightened activity.  Keep it up!  We still really need your help. The accuracy of the avalanche advisory 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 fac.admin@flatheadavalanche.org. Thanks for your help.

 


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 fac.admin@flatheadavalanche.org or call 406.261.9873. Thanks!


DISCLAIMER

DisclaimerGraphic

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.