Experienced widespread cracking and collapsing above 6000 ft.  

Pit dug on NE aspect above Marion Lake.  This pit dug adjacent to collapse and subsequent fracture of weak layer without an avalanche.  Widespread cracking and collapsing on all aspects.  Remotely triggered soft slab avalanche on ESE aspect from about 30-40m away on the flats on the ridge.  Failure layer on all avalanche activity was surface hoar layer about 50-60cm from surface.  On ESE aspects this layer sits on top of a MF crust. 

Image 1: Surface hoar crystals buried about 50-60cm from the surface.  Notice striations on these feathery crystals.

Image 2: Generalized image of snowpack in this area. All avalanches sliding on surface hoar layer.

Image 3: Remotely triggered soft slab on aspects that wrap around from NE to SE.

http://www.dailyinterlake.com/news/local_montana/article_9a90b8d6-5cb0-11e1-95ec-001871e3ce6c.html 

Buried surfaced hoar is still evident on many slopes.  We found this weak layer about 25 cm down from the surface in our snowpits.  On a north aspect, this layer is now sandwiched between new snow and older harder snow.  On east aspects, we also found some evidence of this layer sitting atop a melt-freeze crust.  Our Extended Column Test on a N aspect gave us no results (i.e no propagation).  Our Compression Test yielded CT14 Q2.  

We experienced isolated cracking on E and SE aspects off the ridge. These cracks weren't traveling very far, though.  Wind slabs were present, but not quite slabby enough to move.  However, the surface snow was easily sluffing and moving fast and readily.  A bit more wind and snow and....

We did get a couple of very small pockets of wind slab to move further down where wind in the gully is variable and the surface snow was a bit more slabby. 

Toured to the saddle SE of Mt. Penrose.  Climbed to the chute just SE of the prodiminate one with  the 150 foot rock wall on the skiers left.  My partner and I cut the cornice.  It fractured 20 yards wide and 6 feet deep!  Propigation ended 75 yards down slope.  There wasnt much snow left in the chute.  There was a good size pile when all was said and done.  120 yards wide.  5-6 feet deep. 

Remotely triggered an avalanche on a NE aspect at ~6000 ft. from 20 ft. away.  Crown ranged from 6-18 inches.  Slope was wind loaded from STRONG SW winds (nearby weather station at Shed 7 reported 80+ mph gusts).  Pit dug on avalanche crown.  Failure layer was interface of new/wind loaded snow and old snow.  

Isolated cracking on other aspects as well.  

Flathead National Forest, Kalispell office, 650 Wolfpack Way.

Speakers: Stan Bones & Tony Willits

This was submitted by Ted Steiner.

GENERAL INFORMATION:

Toured today with Jason Grizwold, District Ranger for Glacier National Park, up the southeastern aspect of Mount Shields to the south ridge of “Little Shields.”  Continued on ridgeline to an elevation of 6900 feet elevation.  Touring was slow due to trail breaking in up to 60 cm of new low density and wind transported snow.  Descended northeast exposure of Little Shields to skier’s right treed ridge…  Followed this ridgeline feature to the Fielding Creek Drainage.  Skiing conditions on upper third were excellent, middle third satisfactory, and lower third tolerable but slow going as low density snow was covering (hiding) numerous hazardous obstacles.  

WEATHER OBSERVATIONS:

Temperatures had been warming all night previous to tour and at start of tour air temp at the Canyon floor was

-8C (17F) and at high point air T was -4.8 C (23F).  Light snow showers throughout the day. Southwest winds gusting moderate to strong…  Snow transport onto northeast exposures.

SNOWPACK OBSERVATIONS:

Snow profile conducted on a northeasterly aspect was full depth at approximately 2106 m (6910 ft) elevation on Little Shields.  Snowpack was 157 cm (62 in) consisting of mainly new snow and mixed forms in the upper half of snowpack and mixed forms to well developed facets in lower half.  Hardness in upper third was Fist, middle third 4F+ and, lower third Fist.  In this profile, middle third of snowpack was bridging an otherwise unconsolidated snowpack.  Stability tests were limited to Compression Tests with no extraordinary results.  CT 13 and a CT12 both Q2 were main focus and found on a decomposing crust layer approximately 55 cm from snowpack surface.  This layer was not observed in sidewall profile examination.

AVALANCHE OBSERVATIONS:

No natural avalanche activity observed.  However, low elevation natural activity did occur on 1/19/2012 and was limited to recently fallen new snow on steep cutbanks/ rock faces.  On our approach to Little Shields we did have some localized shooting cracks at lower elevations and occasional audible collapsing.  Cornice drops onto northeast exposures at approximately 1676 m (5,500 ft) resulted in no slab releases.  

There is a lot of alder and brush still showing. The south facing slopes off the Marion Dickey ridge are very brushy. People have been skiing there but you are not going to get a clean shot from top to bottom for sure. The head of the lake looks like a better option but not that day. The wind was pretty fierce once out on the lake. The lower slopes of Essex north face are totally brushy. That said I was able to pick my way through on the exit. Forget about skiing Back Door as the brush is showing top to bottom. Skiing out on the trail was tolerable. Also, the route up to the Middle Ridge from the BMW sign is impassable on skis. Needless to say, we need more snow.

*******************************************************************************************************

Hey Folks,

Since you all follow the weather pretty closely you may already be aware of the big pattern change for next week.  We (NWS) are often pretty cautious and conservative about impacts that far out, but there is high confidence in this event.  Valley impacts are still somewhat uncertain, but the mountains should acquire several to numerous feet of new snow next week with the heaviest likely from Wednesday through the weekend.  During that period the Clearwaters of northern Idaho and the Bitterroots could receive up to 5 inches of SWE.  Models are painting just a bit less than that over the Rattlesnakes and the mountains of NW Montana, but stay tuned.  It will depend on exact placement of the moisture plume of course.

The initial front/upper trough will move in this weekend/early in the coming week, but those typically result in inches of snow.  But later next week we should be talking feet.  Think we are going to mention something to this effect on our Facebook page http://www.facebook.com/US.NationalWeatherService.Missoula.gov.  In the NWS that media is really meant to keep a weather-related conversation going.

Our next posting may generate some comments or questions (hopefully) on how this will afffect the backcountry conditions.  You experts are encouraged to respond or initiate comments on that page.

You are welcome to pass this on to your field observers.

Marty 

Elevation 5800 ft NE Aspect wind 5-15mph w temp 30C

80 cm snow pit depth down to ground

ECT 29 Q1 at the ground

ECT 7 Q1 on Facets under a 10CM ice lens 30cms into the snow pack

Both results in the same pit!!!

Powder conditions with 3-4 inches on the surface with two major ice crust layers with facets below.  ECT tests showed variation within the pit.  Ground was not frozen and mud was soft.  Wind had deposited soft slabs in the area with volital results just below the 10CM ice lensunder a 30cm soft slab.  Forest conditions showed less instability within the shaded and protected areas.  Pit was in an open area with obvious snow loading and transport.  It appears without some investigation that the snow pack is incredibly stable, the deeper you look the less it appears that way.  I am going to say my results were less than conclusive with variability in snow pack and stability.  Let's keep the opbservations coming in so we can all benifit from any data available.  I will continue to post info as I get it.  The parking lots at Autumn Creek, Cascadilla, Rescue Creek and Feilding all had cars parked in them on Sunday.  No visible natural slides or other signs of instability.

Flathead National Forest, Kalispell Office, 650 Wolfpack Way.

Speakers: Stan Bones & Tony Willits.

As the day progressed, lower elevation and S facing aspects became sun affected and new snow turned heavy.  Natural point releases on SE aspects along Marion/Dickey Ridge of Pk. 7798 (photo).  In the mid- to late afternoon, winds from the SW increased to moderate (20-30 mph) thus causing wind loading.

Image 1: Natural point releases on Marion/Dickey Ridge on SE aspect.  Appears as if it tried to pull out a slab on looker's right of slide.

Image 2: Debris from avalanche path into Essex Creek.  Appears to have occurred during last week's wet storm as this debris looks like it entrained a lot of wet, heavy snow as it crossed Essex Creek!  Crown from this slide was about 1/2 to 3/4 of the way up the avalanche path.  

Karl Birkeland, Acting Director and Avalanche Scientist

USDA Forest Service National Avalanche Center 

If you've been at some of the various snow and avalanche workshops or the NAC meeting this fall, you've heard about some of the great graduate work that Ned Bair and Zach Guy have done. Ned recently finished his dissertation and Zach recently finished his thesis.  If you are the kind of person that likes to read about all the details, I've just posted their documents up on the NAC website:

Bair, E.H. 2011. Fracture mechanical and statistical properties of avalanches that fail on nonpersistent snow crystals. Ph.D. Dissertation, Bren School of Environmental Science, University of California at Santa Barbara, 188 pp.   http://www.fsavalanche.org/NAC/techPages/theses/bair.pdf

Guy, Z.M. 2011. The influence of terrain parameters on the spatial variability of potential avalanche trigger locations in complex avalanche terrain. M.S. Thesis, Department of Earth Sciences, Montana State University, 245 pp.  http://www.fsavalanche.org/NAC/techPages/theses/guy.pdf

Great stuff!

Hope you are all having a good start to winter.

Riding at the lake onto or at the end of trail 895H (Near Doris' Point). One area of steep area of slope had previously avanlached. Later another portion of slope let go up to tree line, approximately 6". Against better judgement we decided to stay in area because we observed areas remaining had some tree cover. That area then let go up high and swept one rider off machine who was lower on less steep portion, leaving rider partially buried and sled mostly buried. Area was approx. 100' + wide and about 4-5' deep at bottom. Nearly missed another rider and third rider was in a safe area. In the end we got off very lucky and the incident was a result of bad judgement given signs observed. Very unstable conditions exist. In all cases it appeared that new snow layer released. 

Pit on ESE aspect revealed a thin layer of decomposing buried surface hoar (2-4 mm, ~45 cm from surface in this pit) above an old MF crust that propagated with moderate force in ECTs.  

No propagation on same layer on N aspect in ECTs - no crust present either.  Just a very thin layer of buried variable surface hoar that appears to be decomposing and bonding to adjacent layers (new snow and old decomposing precip particles) on this aspect.  However, did note recent natural avalanche activity on multiple steep N-facing slopes across canyon as mentioned above.  This thin surface hoar layer seems to be variable across space and variable in strength.  

Rain crust on surface to about 5500 feet.  Above that......SNOW!

Image 1: Recent natural avalanche activity on multiple, steep North facing aspects.  Debris barely visible at bottom of chutes on edge of lake.

Image 2:  Snowpit from ESE aspect.  N facing aspect on other side of ridge harbors similar surface hoar layer but not on top of crust and also appears to be rounding.  Quite variable layer it seems.

We saw many natural avalanches today on south west facing slopes starting at 6 to 7000 ft and running to the bottom of the runouts, several across the snowmobile trails.Went on the road to the west of werner peak with several small avalanches across the road. I would agree with the high rating. 

Skookeleel aka Dorothy's on Dec. 26 report of a soft slab, size 2 (60 cm x 60 m x unknown length) skier triggered on a NE aspect on a 35 degree slobe at 6500'. Failure occured by kicking a small cornice block on the NE wind loaded slope, propagating fractures along the entire length of the crown, subsequent release upon approach on skis. Isolated natural releases on similar aspects and elevations. This occured before the recent rain event.

Big Mtn Side Country on Dec. 28 report of natural and skier triggered activity. Apparent natural release on the high road leading from the resort to the pass between Canyon and Big creeks. This is the road above the route skiers return to the resort on coming from Canyon creek. Skiers noted a release from the steep north facing road cut jusst past the resort boundary onto the high road running to the lower return road. This buried an existing skin track put in that morning. This same group then toured towards Gooley's and triggered a release on the steep NE aspect above the small pond by jumping on the ridge. Remote trigger. 18" crown x length unknown.

Erich Peitzsch, USGS Avalanche Specialist, Avlanche Forecaster for the Glacier National Park road crew.

Snowpit (total snow depth on N aspect was 130 cm) revealed a facet/crust/facet sandwich located near the ground in the snowpack. This sandwich is less than appetizing because of the mixed results we saw in our stability tests.  This layer did not propagate in our extended column tests (ECT).  This layer did fracture on the facets above the crust in our compression tests (CT) with moderate force.  So, despite it not propagating, I am definitely keeping my eye on this layer particularly when we have our first notable loading event (i.e. lots of weight added to the snowpack during the next storm).  

Strong wind (gusts over 50 mph....nearly knocking us over)  from the SW was transporting some snow creating isolated windslabs on lee sides of ridges.  These slabs did not appear to be widespread much below the ridges, but there were isolated pockets.  

Avalanche Safety Presentation

--Avalanche Advisories Underway--

The Flathead National Forest is hosting a free presentation about early-season backcountry snow and avalanche conditions in Northwest Montana on Tuesday, December 13, 6:30-9:30pm at the Flathead National Forest Office in Kalispell, 650 Wolfpack Way.  Forest Service Avalanche Specialist Stan Bones will present the evening session.

The presentation will focus on the weather in Northwest Montana, including typical weather patterns, websites that display current mountain weather conditions and forecasts, and how to interpret the data and forecasts.  A discussion regarding the fall and early winter weather to date, and how these conditions affect snow and avalanche conditions will also be held. 

Bones will discuss last season’s conditions and how the weather set the stage for the January 2011 Doris Ridge Fatal Avalanche Incident. Bones will also review how avalanche advisories are formulated, the North American Avalanche Danger Scale and the new local advisory format.

The session will be an open discussion with an emphasis on a question-and-answer format. 

The session is free and open to all.  There is no registration.  Please call the Flathead National Forest at 758-5284 or visit www.fs.usda.gov/flatheadfor more information. 

Avalanche Advisories for Northwest Montana Underway

The Flathead National Forest issues avalanche advisories for Northwest Montana throughout the winter, beginning the first Friday in December or as weather conditions warrant.  Advisories are issued once a week, on Friday mornings, until the third week in December, when they are issued Tuesday and Friday mornings (as weather conditions warrant) until April. Advisories include information about snowpack conditions, weather forecasts, and hazard evaluations. 

Advisories are posted on the Flathead National Forest website, http://www.fs.usda.gov/flathead

and on the Glacier Country Avalanche Center website, www.glacieravalanche.org.  The advisory can also be accessed by calling 406-257-8702.  Anyone traveling in the backcountry will always need to make their own time and site specific avalanche hazard evaluations.     

I suspect these long, dry cold periods are not helping what little snow we have. Maybe a rain storm would be good? Skiing was poor but at least the sun was out. Temps were warm; mid 20's to start the day, mid 30's at the end of the day. The temps were not affecting snow consistency on the surface. Winds were high out of the SW. Travel conditions were easy with minimal penetrations.

 Activity. AIARE Snowmobile LevelI Avalanche Course

Observation. 12 Snowmobiling L1 Students made multiple observations on many aspects and elevations between 5800' - 6400' under supervision from AIARE instructors.

 Obs. Avg Snow depth@ 6000': 85cm. 3 Layers of concern found on varied aspects at 6000-6200':

 1. 10 - 15 cm of 5mm Facets/Depth hoar at ground failed at CTE Q2 in several compression Tests. ECTN in all tests. Note that these failure occurs on a grassy slope with lack of anchoring.

 2. Buried surface hoar/rimed grains @ 20-25 from surface. Found these in 2 test pits over 1/2 mile apart. CTM Q1 in several compression tests. ECTN in all tests. 

 3. Near surface facets at 5 cm from surface are insulated by new snow. Easy Tilt tests identified this layer on most aspects/elevations. Will be a concern depending on how upcoming weather/snow arrives. 

 Results.

Quality riding to be had despite low coverage. Side-hilling on small scale steeper convexities produced no results. We decided to look out for uniform snow cover on slopes lacking sufficient vegetative anchoring. Look out for buried stumps, rocks, and logs!

Good course with participants from Winter Wonderland Tours guides, Border Patrol, local and SAR groups.

Posted by Joe Grabowski from an observation by Ryan Murray with Cascade Powder Cats                           

There are enough ski tracks out there to make the untracked experience nearly impossible. Some skiers are bolder than me. I did observe tracks through the weeds at lower elevations.

Speaker: Erich Peitzsch, USGS Avalanche Specialist, Forecaster for Glacier National Park road crew. 

Tuesday, November 29, 6 to 7 pm.

Whitefish Library.

 Our stability tests showed that this layer has the potential to propagate a fracture with hard force (ECTP 21, Q1).  Partly sunny skies dominated today, but a constant WSW wind (20-30 mph) was transporting any surface snow available for transport.  We experienced no collapsing or cracking today, and did not see any recent avalanche activity.   Ski penetration was ~5-15 cm with a very supportable base underneath.  Overall good skiing to just below 6000 ft.

http://utahavalanchecenter.org/accident_gad_valley_11132011 

I did some XC touring off of the Big Creek road on Saturday and Sunday. Toured up to 6,000' both days and found 12" to 15" with about half of the snow being from the storms over the weekend. On Saturday we encountered blizzard conditions during the afternoon and evening. The snow was mostly grauple and created a slab layer on top. Observed cracking on the snow surface. Touring was excellent.