Building the Colorado snowpack

[pechelman]

random question and observation

the past couple snows here in denver have been sticking around much longer than usual. Normally it seems the snow falls and it all melts the next day. Is this an indication of anything up in the mountains? Or is it just a factor that the snowfall here has been a bit warmer\wetter snow than usual or something else?

Or have I just not lived long enough here in CO to realize that the snow usually does stick around this long in contradiction to the small sample set of data that I have from only living here 2 years?

It still seems unusual to meet that a lot of the stuff I drive by going into work still have significant snow coverage....from the flat plains north of castle rock to a whole bunch of east facing hills just below the foot hills.

I will say its been freaking crazy windy in comparison to what Ive seen in the past 2 years. (esp Thursday night)

[Joey Joe Joe Junior Shabadoo]

Right off the top of my head, I would say you are right to think that the snow usually melts pretty quickly along the Front Range. In the 8 years I have lived here most of it was in Boulder and even the biggest snows usually melted quickly. I would guess it is an indication of colder temps after a storm. Those colder temps(which we have had in the mountains too) usually delays and/or slows bonding of the new snow to the older snow, which in turn can slow stabilization of the upper parts of the snowpack. I have been riding the lifts a lot recently so I don't know how true this is in the bc but some of the recent avi reports from CAIC and the RFAC seem to indicate this as well.

[lemon boy]

I would say that it is more indicative of abnormal snowfall down here coupled with pretty normal cold temps. In the mtns things are seasonably cold.

[FrankZappa]

Wind, Wind, Wind.

Yesterday's tour near Guanella Pass was a story of wind. Windscour much above Treeline other than steep east/SE aspects and below treeline. There varying slabby and punchy windcrusts. Rotten at the bottom anywhere thinner than 30" deep.

I really hate the wind - creates a) extreme variability in depth, b) windslabs prone to slide, c) nasty wind crusts.

I hear what you're saying. Especially above TL combined with east of the divide. While it can make a 4" snowfall thigh deep in other spots through transport (which is frickin' awesome), it's also the culprit creating the loading zone where the avies tend to reside. My experience/education here comes from many years skiin' loveland, home to lots of wind, but in a "controlled" environment.

Wind and it's effect is also the very reason I spend most of my BC time below TL or head to ranges that aren't as prone to the endless pounding from the wind. ie. San Juans.

I used to (and guess I still do) have kind of a theory about the effects the wind has on the individual snowflakes and hence the way that would build into the pack - to a certain extent. What I've been thinking/observing can be witnessed by driving your car or getting out and walking/slipping around on your feet in different locals. Note: In these observations I'm generally speaking of observations during a storm.

Here's what I noted: Up around Loveland I think the flakes get broken down and are likely to be a "smaller" grain size and prolly pack denser. - Cooler temps in general may/prolly play a part here too. I noted that tracktion, in the car and on foot, was pretty good around there. Like small sharp grains.

Now I've been hanging around the Monarch area and when it snows it's generally much calmer, (as compared to Loveland area). The roads are much slicker and the way the snow gets under tires and feet is like an ice rink on a slope. And the pack I think is less dense (blower). Like big flat slipery plates.

In the Wolf Creek area, home of the big overnite dumps, and warm daytime temps, you can almost watch the settlement it's so fast. Here snowfall is mixed a lot but generally fluffly I think due to less wind. Graupel, rime, columns, flakes... all kinds of snow in there. And I think temps play a roll as they seem somewhat warmer.

I'm sure there are other factors, but I just thought I'd throw these observations up.

Some factors: Northern CO seems to get storms out of the PNW, whereas southern CO seems to do better with storms coming from southern CA and Baja regions. Moisture content. Orographics, etc.

So, I guess with and without wind, as far as the pack goes, we get soft and hard slab development. And I the structure of the individual flakes and the way they make up the build I think is pretty heavily impacted by wind.

[FrankZappa]

Well, now I'm thinkin' about all the kinds of crystal formations out there, and what effects they can build into the pack. You know, structure wise like densities and how they might bond to each other.

So, I'm gonna borrow a bunch of great close ups from http://www.lpsi.barc.usda.gov/emusno...ison/comp1.htm and qoute what they say for each pic. While some of these may not pertain to Colorado's pack, I'll put 'em all in cuz they're kinda purdy.

---------------------------------------
Comparative Images of Snow Crystals
This series of scanning electron micrographs represents newly precipitated and metamorphosed snow crystals. The small circular inserts are the "classical" light microscopic images that have been published by Nakaya, Bentley and others. Magnification figures (i.e. 450x) that are indicated on the micrographs are only true for 8" x 10" images. Bars are accurate for all magnifications.


The image that most people have of a snow crystal.


A common snow crystal form; note the double sheet structure.


The column forms across a wide range of cloud temperatures and has many variations including the bullet.


The needle crystal is often associated with heavy snowfall in the Northeastern United States.


This form has been difficult to image using light microscopy whereas LTSEM reveals it's true 3-D nature
The crystal type is sometimes indicative of a temperature inversion layer in the atmosphere.


A combination of two crystal forms; the Japanese Tsuzumi is an unusual variation.


The side plane is only one example of irregular crystals which include broken crystal fragments and abnormal growth features.


Sometimes the original crystal shape coated by rime is apparent, sometimes only an amorphous blob is evident.


Ice pellets commonly occur with other crystal forms near the freezing point.


Small hail that has been fractured to show internal structure.


Sampled shortly after deposition on snowpack.


This wind-packed snow from Alaska's North Slope resembles a 3-D jigsaw puzzle.


The original form is evident but rounding has occurred.


Rounding of original shape is more pronounced.


Some nearly distinguishable forms exist and sintering between grains has started.


Small rounded grains with no original crystal forms evident.


Evidence of both rounding and faceted growth exists.


Initial layered forms are present with faceted crystals.


Layering and hollow interior characterizes this unusual depth hoar crystal.


Another layered and hollow depth hoar crystal with little evidence of bonding.


Obtained in a portion of a melting snowpack with little free water apparent.


Obtained in the surface layer of a melting snowpack with much free water evident.


Firn from South Cascade Glacier.


Glacier ice from South Cascade Glacier.

[smitchell333]

Zappa - some interesting pictures. I think a lot of what's important about the snow crystal structure is what it means for that snow's role in the pack. If its loose and no bonds between crystals it can mean little slab avy danger if its the top layer - ala untouched powder. But if loose and slippery and no bonds on the bottom such as depth hoar and a tense slab lays above it - whuuummmppffff.

Anyone get out today? What aspects above treeline are skiing OK?

[grskier]

Just going to post an observation... Was hiking and skiing in the side country in the Holy Cross wilderness area and saw some amazing (both amount and size) surface hoar. Fun to ski, but could set up as a poor layer once it gets energy on it.

[Below Zero]

12/09/06 - The snowpack on the north facing aspects around the Montezuma area had large crystals of surface hoar. The entire snowpack was sugar above and below treeline.

[~mikey b]

great shots FZ - that's a good resource

[Jer]

Love those crystals, Zappa.

You in CO yet mike?

[~mikey b]

ferry leaves at 0245 tomorrow morning

we'll be on the road from Bellingham Dec 15th, and will likely be in your neck of the woods around the 20th or so.....

meadow skipping?

[MakersTeleMark]

Touring in the Monarch Pass area on 12.10 I found 10-15" of total hoar to the ground. Wind deposited pockets existed with 20ish inches, still hoar. Very thin crusts on isolated aspects. They definitely need snow down there.

[Loudpawlz]

Touring in the Monarch Pass area on 12.10 I found 10-15" of total hoar to the ground. Wind deposited pockets existed with 20ish inches, still hoar. Very thin crusts on isolated aspects. They definitely need snow down there.

On what aspects/area did you observe these conditions? I was at the ski area on Sunday and Monday. They did get a decent acummulation between Sunday afternoon and Monday afternoon.

[MakersTeleMark]

Near and at treeline around and below the cat terrain.

[pde20]

Lots of wind and steady small accumulations this week near Loveland resort resulted in good, though highly variable conditions this AM. ~ 12-15 inches of new snow in sheltered areas with significantly more in wind loaded gullies and rollovers with sensitve soft slabs lurking...at least they were soft below treeline, didn't get above treeline to see if they were any more insidious:



Highly variable coverage too with lots of logs still lurking just out of sight. Be careful out there, particularly this weekend if this storm drops a big new load on us as the newer snow wasn't bonding all that great and there were a couple of times where we were wallowing in nearly full pack facets.

[Jer]

ferry leaves at 0245 tomorrow morning

we'll be on the road from Bellingham Dec 15th, and will likely be in your neck of the woods around the 20th or so.....

meadow skipping?

That'd be fun! drop me an email or PM or just post somewhere obvious as the time approaches.

[FrankZappa]

pde20, is that A tow? Coming down to the interstate behind the lodge about even with LL's parking lot. South aspect then if it is?



Nice shot BTW

[pde20]

pde20, is that A tow? Coming down to the interstate behind the lodge about even with LL's parking lot. South aspect then if it is?

No. East aspect ~ 11,000 ft

[lemon boy]

trelease?

[goldenboy]

I'm just posting b/c as much as I enjoyed the crystal photos, it takes forever for this page to load.

[HikeforTurns]

I'm just posting b/c as much as I enjoyed the crystal photos, it takes forever for this page to load.

Hah, i was thinking the same thing before i read your post, so here's another

[FrankZappa]

Well hell! If we get just 4 more posts, wait make that 3, then we can go straight to the next page.

[FrankZappa]

No. East aspect ~ 11,000 ft

Ohhhhhhhh.... So you were below LL and LL's parking lot.

(2 more)

[FrankZappa]

Watch... some body will "quote" this once we get a new page.

(1 more - who's it gonna be?)

[smitchell333]

To the rescue for new page.