Wednesday, January 25, 2012

Pilot Peak January 23 2012

The skiing at Pilot Peak last Sunday and Monday was described as exceptional by Jim and Erin (Blog contributors). Well, it was no different Tuesday January 23rd. The cold temps and clear nights have kept the surface snow in primo conditions! The New Pow depth was 35 cm.

Below a video of the skiing at Top of The World and Almost Top of the World. Keep an eye for avalanches track at the sides of the ski runs.

The day started as a blue bird day, no wind, cold, ... just perfect. The next two pictures correspond to very first meadow encountered when skinning up from the first pull-out after Mores Creek Summit snowmobile parking area. Notice the outline of the slab (partially covered by new snow) that avalanched last Saturday (Jan 21st).

The slope angle for this slope measured 31 degrees! A picture looking down, above the fracture line is shown below.

This last avalanche cycle affected many slopes where  I would have either expected avalanches to occur higher in the slope, or slopes with 30-34 degrees to be anchored by the heavy brush of Mores Creek Area. Predictably, slopes steeper than 35 degrees avalanched, but MANY slopes in the 30-33 degree range also slided, and crown fractures were sometime found midslope, just as the slope from the pictures above.

The most impressive slide was at Top of The World (or Round the World). This avalanche ran 1300 feet in vertical. In fact the debris field filled and covered all of the gullies at the very bottom of this run and stopped below the elevation at the bottom of "Almost Top of The World" ski run.

I skied to the bottom of the avalanche debris field in complete disbelief ... it ran beyond the alpha angle of 18 degrees, and the extent and size of the debris toe has completely filled the complex gullies. There were trees and brush that were uprooted and have make this ski run longer!

I am going to be conservative and classify this avi as a D3.5R5 - but if you stand at the bottom of the debris field it was obvios that a rail car would have been destroyed (D4). But D4 are NOT suppose to happen at Mores Creek Summit! This most be a 1:20 year event. This winter is my 20 year skiing this area, and I have never seen anything like this at Mores Creek Summit.

100 feet above the toe of the avalanche debris, looking up to Top of the World" 
1/3 of the way up, looking down into the avalanche path, this one of the gullies that channeled most of the avalanched snow.
2/3 of the way up, looking down into the avalanche path
View of the full track down slope from the crown.
We skied two runs at both flanks of the Top of the World Avalanche. The starting zone average angle was 31 degrees, with a steep sections measuring 33 degrees. There is a steeper line with a rollover at 34 degrees above the fracture crown that was not pulled by the avalanche. I typically do my snowpit above this rollover, and was surprised that this avalanche broke lower in the slope than I expected.

South East Flank of the Avalanche.

North East Flank of the avalanche.
Crown of the Avalanche
Full view of the Avi from mid track
Side view of crown
Crown wall made smaller by new 35 cm of snow. Mark standing inside the avi.
There many other significant avalanches from Saturday cycle at the Knob, Almost Top the World (4 avalanches in that area alone), The Lower glades (2 avis), and the eastern flank from the baldy spot we descend to ski the Knob Ridge. This last avalanche was D2.5-3! Just CRAZY!

The new snow at Sunny aspects (NEE, E, SE, ...) had a delicate layer of surface hoar (SH). Please keep an eye on it in case is not destroyed by the new snow predicted by Wednesday. Although, as we skied out yesterday, there was a deposition of 1-2 cm of new snow that most likely already covered this delicate layer of SH. Furthermore, below the snow surface, there is a low density (very skiable) layer of Near Surface Facets called Diurnal recrystallized snow formed by the relatively mild days and cold nights.

I would not trust the avalanche paths once they get a new slab formed. The bed surface was a pencil hard and capped by a slippery and delicate layer of facets.

Thus, for the next storm cycle it is important to track the SH and NSF at the aspects that get some sun. The deep north should be approached with deep suspicion due to the deep instability (buried depth hoar - DH).

Also - and hate to do this - keep an eye on the rain crust layer buried 35 cm down. Between 7000-8000 feet, this layer has formed a well develop layer of large facets. This layer is easy to detect. Testing of it produced CTMQ3 results. A temperature gradient it is still present, thus it might go from a Q3 to Q2. Performing a loaded column test (simulates a storm by loading column with a block of snow) did not changed compression test (CT) test results. Extended Column test did not showed propagation propensity for this layer either.

Sunday, January 22, 2012

Report for Pilot - Jan 22, 2012

Excellent report from a Jim, a long time BC skier:

During our tour today we saw many class 2 and 3 avalanches that occurred prior to Saturday afternoon. Crowns were 3-5 feet deep and bed surface was the late December rain crust. Most slope angles were 35-38 degrees, but one was 31 degrees. Many of the avalanches occurred in the same place where the late December avalanche cycle scoured to the ground, but some occurred where it did not.

This avalanche cycle is thought to be unprecedented in the opinion of our touring party who has skied extensively around Mores Creek Summit for up to 15 years.

Class 3 on mid- to upper-30 degree SE aspect in Round the World Bowl:

Class 2 on 31 degree E aspect:

We stayed on slopes below 30 degrees and found excellent conditions with supportable snow covered by 6 inches of fluff.

Trail-breaking was easy and skiing was fast. Below ~6800 feet a rain crust was present below the fluff.

We were shocked to see a skin track and ski tracks on the Freeman "Exit Chutes". We questioned that decision-making given (1) numerous class 2 to 2.5 avalanches on similar slopes located a few hundred meters N of the tracks, (2) High avalanche danger posted for ranges surrounding the Boise Mtns. and (3) the plethora of low-angle slope options in the Mores Creek Summit area.

Chago comment:

Yesterday (Saturday 1/21) I was quite surprised at the sensitivity of the snowpack. Agree that this level avalanche instability is unprecedented for Mores Creek Summit. I hope you do not mind posting your comments, since they will contribute to create awareness.

In addition, a week ago I was surprised at the sensitivity of the snowpack at Banner Summit/Copper, and that was prior to the BIG snow event. I am spending next weekend at Norway-Halfway-Oregon, and it is very likely that I will have to tip-toe around the big stuff over there.

Readers of the this blog, please take a look at this avalanche accident report:

Avalanche Fatality - 2012/01/18 - Colorado - Burnt Mountain Near Snowmass Village

The avalanche that claimed a life on this accident was very small, and typical to the terrain that can be found at Mores Creek Summit:

The avalanche was 14 feet wide, ran 30 vertical feet, and was 2 feet deep at the crown. Please carefully evaluate any slope you are about to ski, and have the presence of mind to anticipate consequences, particularly during this period of deep instability.

Another blog reader posted the following comment I think it is important to integrate into Sunday's report:
I skied Pilots on Sunday as well. Saw a large slide over on Freeman on a NW slope. The north bowl of Pilots had slid as well, with a 4-5ft deep crown-line and looked to be wider than a football field's length. However, heard no whumpfing while skinning up the ridge to Pilot's. We opted to ski low-angle (<28 degrees) south-facing aspects, and had a fun ski day! 
We also observed several snowmobilers out and about - some were high-marking up on Freeman's on slopes with similar aspects to the slope we'd seen a slide on. EVERYONE should be careful in the backcountry right now, snowmobilers and skiers alike!
That said, low-angle, south-facing slopes are skiing very well right now with an awesome layer of new snow!
-Erin L.

Saturday, January 21, 2012

Mores Creek Summit - Jan 21 2012

Today I drove to Mores Creek Summit to assess the impact of the significant precipitation event, as well as making turns in a set of new skis that have been patiently waiting for the right conditions.

My new POW tool!
As we all know the precipitation that commenced Wednesday and winded down today brought the snow levels to average conditions:

The Snotel at Mores Creek Summit reported a whopping 75 inches, an increase in excess of 48 inches (4 feet!). It was no surprise that some pull-outs were not plowed (such as Winter's Corner), and that the parking area at the Summit was limited in parking space. With very few options available I decided to make few laps at Freeman. There was another party at Freeman that selected to put an uphill trail on the main ridge. I still was not sure there was not going to be combat with the brush approaching from the ridge, and opted to built a second uphill track close to a run some call "Elevator" (ski line dropping to the switchback). As expected, trail breaking required more work due to the unconsolidated nature of the new snow.

No whumpfing, cracking, or other sign of instability were present during the climb and approach via a NE subtle ridge to the 7000 feet level. During the drive, and ski touring, crown fractures were visible at SW, W, NE, NW, and N aspects. The fractures appeared to be 25-30 cm deep that ran during the storm cycle only at very steep 37-39 degrees slopes between 6000-7000 feet. Terrain above 7000 was obscured and/or not visible. NO avalanches were observed that might have run on the old snow interface.

Some brush still poking out even with 4 feet of new snow!
Mores Creek Summit Winterland

I was very fortunate that the camera worked early in the day, and allow me to record the PST (Propagation Saw Test) and Ct (Compression Test). After finishing the the snowpit, my Nikon point & shoot refused to work - it reported a "lens error". Too bad, since it did not allow me to document the several areas with crown fractures.

Below a video for the PST test in a 26 degree slope with East aspect. As you will notice in the video, I was surprised by the propagation at the interface between the New snow and old facet layer (~65 cm from the ground) after just sliding the saw )blunt side) less that 5 cm. The slab experienced a sudden collapse after the propagation, suggesting a Q1 score.

The next video is for the compression column test. A previous test, not recorded resulted in a CTVQ1, or column failure during isolation. On this video, a second column was isolated and failed after just placing the shovel blade in top of the column, perhaps between a CTV and CT1Q1.

This was a surprise to me, to find the deeply buried facet layer so sensitive at relatively low elevation (6800 feet) and after being buried so deeply (1.3 meters) by a slab.

Snowpit: New snow from 65 to 195 cm

Between 65 and 155 cm the snow was 4 finger hard, and fist hard from 155 to the surface at 195 cm. A very thin and delicate rain crust was present 20 cm below the snow surface.

The weak layer - a fist hard 2 cm layer of large facets - was found above the pencil hard ground to 63 cm old snow layer.

The snow pit work did not detected any remarkable or reactive layer in the new snow (top 1.3 meter). While skiing down in terrain 30-32 degrees, no new snow surface instabilities were detected, and ski cutting in wind loaded and steep roll-overs did not produce results.

Considering that evidence of "deep" instability was found:
  • high probability for trigger likelihood (Easy CT scores)
  • high probability for fracture propagation (PST 5/100 End)
  • high likelihood of slip after fracture nucleation and propagation at a depth of 1.3 meter (Q1 Scores)
It would be prudent to approach steep slopes ( greeter than 35 degrees) at Mores Creek Summit Area with a high level of prudence. And slopes that have avalanched this season should be considered suspect-ful (Freeman-42, Almost Top of the World, Head waters of Edna Creek, ...).

Last weekend a second Avalanche L1 course was completed by Pedro and I. We had a good time at Freeman on Saturday, and a fabulous day at Banner Summit on Sunday.

Students at Freeman (Top) and Avi Instructors demonstrating companion rescue.
At Banner Summit, there was about 25-30 cm sweet POW snow (not facets!) that was skiing incredibly well in top of the old facets.

Carl 3X - enjoying the turns last Sunday!
Results for trigger likelihood (CT), and slip likelihood (Q) were moderate CTMQ2 at the students snowpits. However, the propagation likelihood was high (ECTP, PST 40/100 END). Recent avalanches were spotted in the vicinity, thus we restricted skiing to slopes below 35 degrees.

Carl and Judy gathering data.
Pedro with a couple of students at Banner Summit
Thus, it appears that the reactivity of the winter drought facet layer along with its ability to propagate fractures failures will stay with us for while. :(

I would like to take a few lines to congratulate the students that completed the AVI L1 course last MLK weekend. And knowing that they enjoy this blog, I will include few pictures below for their enjoyment. Thanks Judy for the PICS!

Thursday, January 5, 2012

Playful Skiing at Freeman Peak - January 4 2012

We might not have an abundance of snow in South Western Idaho, but once you get above the 6500 feet, the snowpack has been generous, and there are some great turns to be made. Check the video link included below:

Not only the skiing and the snow quality was great, but I spent the day with Pedro (my son), John T. college kids, and the always funny Mike L.

Ski partner approaching Freeman Summit, with great views of the Boise Mountains to the East.
There were no signs that Freeman has been skied after last week storm cycle. And we had the full hill for us today. The best skiing was between 6500 and 7500 feet at protected slopes.

Ramp above 7000 feet leading to Freeman Summit.
A thick layer of "diurnal re-crystalized" crystals (or Near Surface facet-NSF) between 6500-7500 feet in elevation suggest that the warm temps experienced lately have not resulted in a crust or melt/freeze metamorphosis at this elevation range.

The snow above 7500 feet, even at protected north aspects showed signs of densification or the formation of a crust at NE and East aspects. We observed air temps up to 4-5 degrees C by mid-day. This is very likely the result of the "inversion" due to the mild and tranquil weather, thus somewhat cooler temps at mid-elevations is making skiing fun and forming very skiable NSF crystals, but warmer temps at higher elevations is making the skiing experience "instruktional" with its variety of crusts - Bummer!

Below the snotel temp data for Mores Creek Summit (6100 feet) for the last seven days documents very well the balmy temps (above 0 deg C) since January 2nd. Similar temperature trends can be observed at most snotel stations. In fact, reports froms a Boise friend that skied Copper Mountain last Tuesday confirmed that the warm weather negatively affected skiing there.

Below few pictures we snapped today of the last avalanche cycle at Freeman:

Slab fractures - one of the several observed.
More fractures.
And more fractures, and missing slabs that avalanched.
Crown fracture (top left) with debris (center).
Some of us are very fond of the steep but short chutes 600 feet below Freeman Summit. It is important to remember that these chutes are called by some us 42's for a reason, they measure 42 degrees in steepness. Below a series of pictures of one of the chutes:
Crown of avalanche at 42.
Track and flanks of avi at 42.
Debris field and toe of the avalanche at 42.
Deep debris field due to a very dangerous "Terrain Trap". The trees at the Left side of picture are taller than a person.
Stability test results at East Aspects at 7400 feet resulted in ECTX and CTN results. Last Saturday, the buried depth hoar and facet layers were moist. During the last four days, the buried layers have gained strength as the snowpack has refrozen.

Stability test results at the crown of the Avalanche at 42's slope resulted in CTN scores. It was quite interesting to observe at the crown fracture, the presence of a distinctive layer of what was free water frozen (this is a deep north slope) and with an appearance of water flowing between the slab and weak layer.

Three meters away from the flanks of the avalanched slope at 42s, another nearby slope produced stability results with CTVQ2-50 cm down (DH) and CTMQ1- 50 cm down (DH) scores. This was very concerning, since a CTV represent a spontaneous block failure during its isolation. In other words, considering that 42s aspect has a North aspect, we need to continue to be suspicious of slopes steeper than 32 degrees at protected slopes and with North aspect component.