Building the Colorado snowpack

**Sir Jongalot** · 01-14-2007, 04:30 PM

Originally Posted by telemike

Minturn was in the clouds when we left this morning, but Vail Pass was bluebird. Managed to get in a couple runs off Ptarmigan and it was goood.

How was the snowpack looking - good for kickers?

**smitchell333** · 01-14-2007, 04:32 PM

?
1/13/06 I was out Indian Peaks 8600 to 11600. Found better than average snow depths and overall coverage. Stability wise it was a bit on the sketchy end - below treeline it was inverted with substantial depth hoar underlying anywhere it wasn't bare ground 3 weeks ago. Hollow and although a touch of a drumming in spots, NO whumphing heard. Above treeline what was still there was hard as a rock.

Good news is if this settles down decently - esp with any significant warming - it stands an excellent chance of mostly bridging over the sheit.

Good skiing with 2-4" of new on top.

**FrankZappa** · 01-14-2007, 08:00 PM

I'd think it'd be tough to get "any significant warming" especially in the high country mid winter like this. Maybe on southerly aspects with some solar radiation... ?

If what I read in Trempers books and my memory serves me right... doesn't some positive metamorphism happen within the pack if the TG over X distance happen when it is very low (I forget what it is but like a couple degrees)?

I would think that happening in some of the buried old surface facets and such would be more likely to help in the mid pack and with the bridging process (if bridging is what I think it is).

**FiveLarge** · 01-14-2007, 10:27 PM

Originally Posted by telemike

Minturn was in the clouds when we left this morning, but Vail Pass was bluebird. Managed to get in a couple runs off Ptarmigan and it was goood.

I think you've referred to Ptarmigan a couple of times...just so I'm sure that I know what snowpack area you're describing, are you referring to Ptarmigan Hill near Vail Pass (12,143)? If that's giving anything special away, feel free to PM me.

**~mikey b** · 01-15-2007, 09:19 AM

Originally Posted by spthomson

I think you've referred to Ptarmigan a couple of times...just so I'm sure that I know what snowpack area you're describing, are you referring to Ptarmigan Hill near Vail Pass (12,143)? If that's giving anything special away, feel free to PM me.

I am referring to Ptamigan Hill near Vail Pass. I didn't think it was much of a secret, but considering that my partner and I had the only tracks on it on Saturday.............

**smitchell333** · 01-15-2007, 10:45 AM

Originally Posted by FrankZappa

I'd think it'd be tough to get "any significant warming" especially in the high country mid winter like this. Maybe on southerly aspects with some solar radiation... ?

If what I read in Trempers books and my memory serves me right... doesn't some positive metamorphism happen within the pack if the TG over X distance happen when it is very low (I forget what it is but like a couple degrees)?

I would think that happening in some of the buried old surface facets and such would be more likely to help in the mid pack and with the bridging process (if bridging is what I think it is).

Well - we have had substantial warming in Dec and Jan before. One of the best B/C winters I remember was 1996/97 - we had a 60" base by Xmas and on the 27th or so we had temps upwards of 50 deg F at 10K - Made for stellar stability on all but the highest/shadiest faces once it refroze solidly.

But - you are right that with time and with sufficient weight the mid pack will tend to consolidate or bridge. Temps sure can help though.

**iskibc** · 01-15-2007, 11:54 AM

Originally Posted by telemike

I am referring to Ptamigan Hill near Vail Pass. I didn't think it was much of a secret, but considering that my partner and I had the only tracks on it on Saturday.............

No, it's no big secret. It probably doesn't get much traffic because it's a fairly long approach. Everytime I've been up there I've only seen the cat skiers hitting the obvious stuff. Some great touring up in there.

**Buster Highmen** · 01-15-2007, 05:38 PM

Originally Posted by FrankZappa

If what I read in Trempers books and my memory serves me right... doesn't some positive metamorphism happen within the pack if the TG over X distance happen when it is very low (I forget what it is but like a couple degrees)?

Generally, rounding will occur at low vapor pressure with crystallization occurring more in the crevices than the points of the crystal. The delicate, spikey crystals will generally only form at a high vapor pressure.

At least according to freshman thermodynamics. And Sturbie.

**FrankZappa** · 01-22-2007, 02:02 PM

1) Who's Sturbie? ^^^

2) If I'm translating what the observer told me on Wolf Creek on Sat correctly when we came across him in his pit, the 220cm pack there is basically going isothermal (I didn't bother to check for myself)... and it was bomber ('cept for that buried surface hoar layer - but it's almost bridged over that as far as triggering goes I think).

**Hacksaw** · 01-22-2007, 04:14 PM

Originally Posted by FrankZappa

1) Who's Sturbie? ^^^

Craig Sterbenz = Snow Safety Director Telluride Ski Area

**FrankZappa** · 01-30-2007, 12:36 PM

It seems to me that there's almost always a mid-winter lull in the storms, such as what we've had these last few weeks. With a "deeper" pack I would think that things settle down and generally become quite bomber. With a less than desireable thin pack I'm not so sure it can be trusted as much... all other factors considered of course.

There's been a few words said lately coming in from various corners of the state about some of the "unexpected" sluffs and such about the pack on different aspects...

And with the ever greater influx of thrill seekers out there these days said lulls can make the back country look like a feeding frenzy has taken place. I've noticed this frenzy phenonomen mostly around Silverton the past few years - and the latest report is in, as exerpted from an E-mail I recieved:

We did a tour on Red yesterday ....... Hung out at treeline and had lunch until everyone got cold, didn't take long. Must have only been 15 degrees in the sun. Snow on the black rocks in the sun was barely melting. ........, really nice firm snow similar to WC in the open glades and gullies. ........

Seems like the best snow is in the open glades and slide paths. The trees are facets from top to bottom in most places. Of course, there are layers of hidden facets in the open areas and that's where the danger lurks.... People are laying tracks down in almost every slide path along the 550 corridor. Nuts, but sure looks like fun! Tracks on Kendall. 4K! All it takes is a crotch rocket or high speed quads.

My pals evaluation and the thin pack and associated characteristics would keep me pretty leary of a lot of lines in that neighborhood, especially with this years build (being a little below average) - generally speaking here. What say you?

So, I wonder how many folks actually have some kind of evaluation process in place in this frenzy... or just follow the tracks of an other and jump right in? Sucker pack? ... could be [shrug].

**~mikey b** · 02-11-2007, 08:31 PM

Snow off and on all day at Vail Pass - getting heavier as the day went on. There was a few inches of new by the end of the day. Warmish and wetish out there today. Surprisingly good skiing on Shrine Mtn, especially considering how crappy it was Fri and Sat.

T'was snowing at Vail Pass, snaining in Vail when we came through around 5pm, rained all day in Minutrn.

**~mikey b** · 02-15-2007, 06:44 PM

NOAA is posting an Winter Storm Warning and an Avalanche Watch from the CAIC this afternoon.

CAIC is forecasting that the avalanche hazard will rise to HIGH in the Front Range and Vail/Summit County areas this weekend.

Snowpack Discussion

Snow accumulations are around one to two feet with the most around Vail Pass. The Vail area will get the most snow tomorrow, as well. Observers are having a hard time measuring snow before it can blow away. Ridgetop gusts are in the 50-60 mile an hour range and sustained winds 25-35 miles an hour. Tomorrow, the winds really start to blow. All the recent snow has turned into windslabs on most slopes. Strong winds will accompany snowfall over the next few days, so additional snow will just thicken the slabs.

The avalanche activity observers can see has been shallow, running in the recent snow. The slides are sensitive and propagating fairly wide. Sympathetic avalanches occurred on E-SE-S aspects, running on a slick sun crust. There are a few locations where the recent snow has bonded to the underlying old snow and is reluctant to move. The key seems to be a layer of low-density snow under the slabs.

The avalanche danger will be increasing, and stability deteriorating, through this storm. With the forecast snow amounts and winds, we could see a natural avalanche cycle tomorrow. I am issuing an Avalanche Watch this evening. If we do get the forecasted snow amounts, expect widespread natural avalanches on Friday. With the changing conditions, you will need to analyze conditions continually. Be aware of the terrain above you and how it might load. Careful route finding and good travel habits are mandatory. Stay on low angle terrain well clear of steep slopes.

Avalanche Danger

The avalanche danger in the Vail/Summit Zone is rising towards HIGH on all aspects near and above treeline, and CONSIDERABLE on all aspects below treeline. Avoid traveling in or below avalanche terrain.

If you have observations from this area, or any other, please send them to caic@qwest.net

Sun & Mon at Vail Pass, I was seeing snow that was failing fairly easily in shovel shear and compression tests. All this new snow and wind loading may really tip the scales.

Have fun and be safe this weekend.

**Blurred** · 02-15-2007, 07:38 PM

The avy danger going up at vail pass/vail is interesting. I personally don't really consider sloughs as avis. I mean snow moves whenever you ski steep and deep.

Tomorrow the danger will go up, but from everything I've observed and read, it's only affecting areas disturbed by the wind. Wind slabbing and loading will be huge and will have big results. However, I feel like areas sheltered from the wind will be fine. It requires loading to slide, and this recent snow has not been exposed to warm temps, wind or anything else to load it up....so yes, in protected areas it will slough in areas steep enough, but nothing life threatening beyond the usual.

Now exposed areas are another story. DO NOT GO ABOVE TREELINE TOMORROW.
Plus I'm guessing the leeward side will be the only side with snow due to the 80 mph gusts.

**FiveLarge** · 02-15-2007, 08:12 PM

Originally Posted by BlurredElevens

The avy danger going up at vail pass/vail is interesting. I personally don't really consider sloughs as avis. I mean snow moves whenever you ski steep and deep.

Tomorrow the danger will go up, but from everything I've observed and read, it's only affecting areas disturbed by the wind. Wind slabbing and loading will be huge and will have big results. However, I feel like areas sheltered from the wind will be fine. It requires loading to slide, and this recent snow has not been exposed to warm temps, wind or anything else to load it up....so yes, in protected areas it will slough in areas steep enough, but nothing life threatening beyond the usual.

Now exposed areas are another story. DO NOT GO ABOVE TREELINE TOMORROW.
Plus I'm guessing the leeward side will be the only side with snow due to the 80 mph gusts.

In the spirit of discussion/learning...

1)I'm not sure at what point the scale tips...but sloughs, when big enough, can still bury, right? And enough sloughing could be the load that tips the scales in the pack and causes a step down, yes? (I understand and agree with what you're saying...if you're skiing steep, some snow is going to move). Maybe it's a matter of terms...I think of a slough as ONLY the new/surface snow moving.

2)With the winds they're forecasting (which don't sound like they'll affect Vail Pass area as much as stuff closer to the divide), I would think even "wind sheltered" areas will still see some wind affects. That aside, with 1-2 feet already having fallen in Eagle, and another 1-2 forecast through Friday night, even without any windloading in wind-sheltered areas, wouldn't that be enough loading on its own to tip the scales? I know it's been somewhat (relative) gradual...I think tomorrow won't be as gradual...temps have been colder since the start, which isn't helping stabilization...

**~mikey b** · 02-15-2007, 08:13 PM

I think part of the reason for concern is that it is gaper-rific holiday weekend. Folks who have no idea what's up will be farting around above treeline and in heavily wind-loaded areas this weekend.

I bet there will be some fun turns to be found, too.

**Blurred** · 02-15-2007, 08:53 PM

Originally Posted by spthomson

In the spirit of discussion/learning...

1)I'm not sure at what point the scale tips...but sloughs, when big enough, can still bury, right? And enough sloughing could be the load that tips the scales in the pack and causes a step down, yes? (I understand and agree with what you're saying...if you're skiing steep, some snow is going to move). Maybe it's a matter of terms...I think of a slough as ONLY the new/surface snow moving.

2)With the winds they're forecasting (which don't sound like they'll affect Vail Pass area as much as stuff closer to the divide), I would think even "wind sheltered" areas will still see some wind affects. That aside, with 1-2 feet already having fallen in Eagle, and another 1-2 forecast through Friday night, even without any windloading in wind-sheltered areas, wouldn't that be enough loading on its own to tip the scales? I know it's been somewhat (relative) gradual...I think tomorrow won't be as gradual...temps have been colder since the start, which isn't helping stabilization...

All good thoughts.

From what I've observed, the sliding surface is the layer that got baked in the sun for the huge mount of time before this recent snow. Everything that has fallen on that surface is recent, and doesn't have energy. 3 feet of light blower imo is definitely not enough to cause step downs or anything of that nature. Now wind effected snow on the other hand consolidates, creates bonds of slab, and creates load. (which I refer to as energy) Altogether different story.

As far as sloughs go, I'd probably have to speak to you in person about it. I wear my fingers out discussing them here.

Z · 02-15-2007, 10:52 PM

I think you are right on blurred....good points.

On another note, I am personally starting to realize that the best day to ski bigger lines in the CO BC is the day of, or after. When we get this blower snow with no cohesive slab or huge wind event that always happens 2 days after, all you get is sluffy pow.

There. I said it.

**FiveLarge** · 02-16-2007, 07:43 AM

Originally Posted by Z

I think you are right on blurred....good points.

On another note, I am personally starting to realize that the best day to ski bigger lines in the CO BC is the day of, or after. When we get this blower snow with no cohesive slab or huge wind event that always happens 2 days after, all you get is sluffy pow.

There. I said it.

Again, not looking to criticize argue...

Perhaps the "There. I said it" comment was made with this in mind (dunno)...but the first 24-48 hours after a storm with "enough" snow to create a load that pack must adjust to (enough depends on many variables of the existing pack, and the new that is falling) are when the bulk of avalanches occur (obviously, not including wet slides, and slides after a wind event...which, yes, again mostly occur in the first 24-48 after the wind event.

The snowpack needs time to adjust to a new load, and for energy of new snow to ease. Again...how much load and how much energy is dependent on many factors...and I'm not saying it's inherently a death sentence to ski after the first 24-48...but it is when the most avies occur...even in CO.

**FiveLarge** · 02-16-2007, 07:45 AM

Originally Posted by BlurredElevens

As far as sloughs go, I'd probably have to speak to you in person about it. I wear my fingers out discussing them here.

I would enjoy discussing in person sometime...

**FiveLarge** · 02-16-2007, 09:55 AM

Oh, and trust me, I'd rather be skiing right now...

From the Crested Butte avy center, regarding the avy on Snodgrass 2/14:

Skier triggered avalanche, large in size. It started as a sluff at the top and stepped down to trigger the slab. One skier was partially buried but dug himself out. Around 10,000 on a NE aspect. Observed several loose snow avalanches.

I realize the CB pack is not likely the same as the VP pack...but, nevertheless, demonstrates that sloughs can have larger consequences than just the new, loose snow...

**smitchell333** · 02-27-2007, 09:37 AM

Underlayers are almost totally rotted anywhere its less than 6 or 7' deep. Higher elevation deep drifts are the only thing I've see that isnt hoared bad. We need some warm temps to settle this thing out - that or lots of snow.

**goldenboy** · 02-27-2007, 10:52 AM

Regarding sloughs- In general, they don't concern me and they often add a really fun element, BUT with a rotten pack they can be trouble. Don Pedro started this slough on the climax chutes outside of CB on a ski cut. The slough stepped down into a fracture and ran full track. These photos are from the CB Avalanche center (there is a good collection of photos there- the Robinson basin ones were caught on film for Thrillhead Creations next movie- the skier was lucky to grab a tree and not go over the cliffbands)

**HikeforTurns** · 03-01-2007, 06:47 PM

Some crazy wind transport going on from pretty much Avon to Evergreen during my drive home today. keep an eye out.

**Avalanche_Observer** · 03-02-2007, 10:55 PM

Right on - with about 30" of new snow along and west of the Divide over the past week, there's lots of snow available for transport. Couple the new snow with the sustained winds of 30 MPH with gusts as high as 50 MPH from the west, and watch for significant loading on east facing aspects. Look for new loading to take place over the weekend on south facing aspects as the winds turn northerly and northeasterly. Many south facing aspects along the Front Range and Summit County areas have a variety of buried crusts from warm temperatures a few weeks ago.