2008-2009 Colorado Snowpack Observations

**Rontele** · 10-15-2007, 12:49 PM

We'll start a new thread. The only observation this cube jockey has today is that it snowed yesterday.

Edit to add: The forecast for this week 10/15 -10/22 looks promising with a long wave trough setting up over the western conus ejecting short waves into CO in the Wed-Thursday time frame. Orographics on Wed/Thurs look favorable from the WNW (slightly less favorable for SuCo). Looks like a brief transitory ridge on Friday before another system for the weekend. The GFS wanted to cut this low off over Eastern Colorado, but the ECMWF is more progressive with the system, which seems more likely given the building high pressure from the west. After this weekend, the high pressure looks to take hold for the remainder of the month.

Here are some good links:

CAIC
NOAA Homepage
Climate Prediction Center Products Page
CPC QPF page
Colorado Data Page
Colorado Forecast Discussions
Colorado SNOTEL data
Animated GFS and jet stream maps courtesy of the Canadian Avalanche Center
iskibc ski blog
USFS Fireweather Information Website Interface is a little difficult, but gives some great forecasting tools, which are also found on the NWS pinpoint, interactive page. (thanks to Halsted for finding this)

**pechelman** · 10-15-2007, 03:38 PM

can anyone comment on the recent snowfall

wet & heavy?
sticking around?
melting off?
aspects?
wind?
how well do they make pina colada snowballs?

excellent job on creating yet another worthwhile thread D!

this might be better than those 3298 other ones about poop

**lemon boy** · 10-16-2007, 10:36 AM

I would guess by sunday night there was >12" above say....9,000' -9,500' in grand county.

Fairly heavy, at least by Colo standards.

edit- steep very northerly shots above treeline were still holding snow as of Sat as well.

**~mikey b** · 10-17-2007, 05:58 AM

anything to get the Nike spam off the main page...

hoping to get out and poke around Vail Pass this week just to get a sense of the start of the base - been stuck in Glenwood while my wife worked at the hospital the last few days

**Rontele** · 10-17-2007, 08:01 AM

Persistent WNW flow through tomorrow, then ridging before a strong cold front moves in on Saturday. Models still disagreeing over some of the features, but the barclonicity--at least--is showing up in both the GFS and EC models. There are actually some hints of retrogression of a closed low, but that seems unlikely.

**pechelman** · 10-17-2007, 08:46 AM

dude, D

if you understand what baroclinicity means, you're quite the closet enginerd cause I had to look it up.

What does this resultant atmospheric vorticity mean with regard to the snowpack?
Finer grain snow? Drier? What will this do to the prevailing persistent WNW flow? (in terms of wind loading)

and if all of the models seem to agree on baroclinicity, it must mean that it has pretty large vertical entropy gradient. (ie vertical atmospheric shear)
besides inducing vorticity, what other implications does a large cold air mass moving down have for this early season snow? (hoar?)

**Rontele** · 10-17-2007, 09:50 AM

Originally Posted by pechelman

dude, D

if you understand what baroclinicity means, you're quite the closet enginerd cause I had to look it up.

What does this resultant atmospheric vorticity mean with regard to the snowpack?
Finer grain snow? Drier? What will this do to the prevailing persistent WNW flow? (in terms of wind loading)

and if all of the models seem to agree on baroclinicity, it must mean that it has pretty large vertical entropy gradient. (ie vertical atmospheric shear)
besides inducing vorticity, what other implications does a large cold air mass moving down have for this early season snow? (hoar?)

A good wind event, which they are expecting will load the lee slopes-- -E/SE in this case. All that is really happening now is the building of the initial base. Hoar is not really an issue unless we get a long spell of cold, clear nights. My worry is that we should see some decent snows through the weekend, then a large high pressure builds in by the beginning of next week. Yesterdays long-range forecast had it holding through the end of the month.

**FrankZappa** · 10-17-2007, 10:03 AM

Hey D, would you put a bunch of links to weather sites in the first post so they're easy to find.

I lost all my old ones the other day when my hard drive took a dump.

For the record, since we're talking weather (is this the CO weather thread?), the way this system is acting now, and over the last 12-15 hrs, is making for great "Monarch" district winter weather. Pumping right up in and targeting the pass area. Just thought you might want to know for future reference, since so many of you get some free days at Monarch with the Loveland passes.

As for the pack, there has been hardly a flake around this end til now. So we are set for a premo base if it'll start stacking up over the next week or two without going to the crap side.

**pechelman** · 10-17-2007, 10:04 AM

I guess i was asking what significance is the baroclinicity.

im on board with the prevailing winds loading those aspects, but baroclinicity brings vorticity so i was wondering how much and if to any extent, this windload will be change. It would also seem that if the snow remains airborne longer, in a high energy \ entropy atmosphere, that the snow would be broken down into smaller particles and dried further (maybe?)

I was also thinking that since this new snow might be dried and cooled a lot by being airborne potentially longer within this cold air mass, that a larger temp gradient would exist between any remaining snow, the ground, and this new snow.

im probably just over analyzing, but im just trying to understand the importance and implications of a baroclinitic atmosphere to the snowpack, since its a new thing to me

2nd question
how common are baroclinitic events in CO?

**Rontele** · 10-17-2007, 10:24 AM

Originally Posted by pechelman

I guess i was asking what significance is the baroclinicity.

im on board with the prevailing winds loading those aspects, but baroclinicity brings vorticity so i was wondering how much and if to any extent, this windload will be change. It would also seem that if the snow remains airborne longer, in a high energy \ entropy atmosphere, that the snow would be broken down into smaller particles and dried further (maybe?)

I was also thinking that since this new snow might be dried and cooled a lot by being airborne potentially longer within this cold air mass, that a larger temp gradient would exist between any remaining snow, the ground, and this new snow.

im probably just over analyzing, but im just trying to understand the importance and implications of a baroclinitic atmosphere to the snowpack, since its a new thing to me

2nd question
how common are baroclinitic events in CO?

You are engineerding this, P.

Shocker. Baroclinicity happens anytime there is a cold front. I think unless you are an avy professional, getting VERY scientific about weather and snow can be more of a hinderance. I put links at the top of the page.

**pechelman** · 10-17-2007, 10:55 AM

I like science
Sometimes I ride and ski for it.

point taken

**Hacksaw** · 10-17-2007, 11:56 AM

Originally Posted by Rontele

I think unless you are an avy professional, getting VERY scientific about weather and snow can be more of a hinderance.

LOLROF

No, D. is not an Avy Professional..... But, he is a professional in another occupation.

**Rontele** · 10-17-2007, 01:14 PM

Originally Posted by Hacksaw

LOLROF

No, D. is not an Avy Professional..... But, he is a professional in another occupation.

Glad I could make you smile. I am no avy professional and marginally a professional at my other job. But for us avy jongs, I think it is important to keep what is important in front of you and not lose sight of the forest for the trees...

**~mikey b** · 10-19-2007, 03:33 PM

I had to get out and take a look around before the next storm hits. Didn't have a partner or a ton of time, so I kept it close to the road. Went out Corral Creek to Uneva Pass. There was a skin track - fucked up by postholers - and a few ski tracks. The south facing stuff had about 35-50 cm of mostly new snow. Winds have been moving snow, and the cornices are already starting to form. North facing is probably holding more and better snow....

At about 11000', there was about a 1cm melt-freeze crust right above the ground, with a little bit of hoar crystal formation below the crust.

Up higher, at about 11900, that crust was not eveident.

Pretty thin and dodgy, but some fun turns were had. Great to be back out on snow for the first time this season, and for the first time since my shoulder surgery.

**~mikey b** · 10-19-2007, 03:43 PM

fixed 'em

**smitchell333** · 10-19-2007, 05:02 PM

Originally Posted by Rontele

A good wind event, which they are expecting will load the lee slopes-- -E/SE in this case. All that is really happening now is the building of the initial base. Hoar is not really an issue unless we get a long spell of cold, clear nights. My worry is that we should see some decent snows through the weekend, then a large high pressure builds in by the beginning of next week. Yesterdays long-range forecast had it holding through the end of the month.

Berthoud 10/19

12-24" on the east facing above the pass, 0-10" below the pass. Noticeable depth hoar development beginning on the bottom layer. Its pure math at this point.

Temperature gradient, thus moisture transportation, and thus depth hoar development is happening any time the average temp below 0 deg celsius/10cm of depth in a given location is greater than 1 deg C/10cm. In other words anytime the temps are significantly below freezing we are developing hoar.

At lower elevations with just a few inches this happens pretty fast.

More snow is better, so pray for more!

**FrankZappa** · 10-19-2007, 05:13 PM

I think we may be getting a favorable series of systems going. Seems to me we've been lining up a couple per week lately and if it'll keep up it til we get a couple few feet on the groung it could be good.

Also, days like today with the warming chinook like wind in between instead of the deep freeze seems good too.

As long as that TG and some frozen stuff by the ground stays down there in a minimal state I can live with it. That kind of stuff I see at Wolf Creek a lot and we all know about the pack there...

**Jtoke** · 10-20-2007, 07:18 AM

East Red and Buffalo below treeline have some nice lines.

**smitchell333** · 10-20-2007, 05:28 PM

Originally Posted by FrankZappa

I think we may be getting a favorable series of systems going. Seems to me we've been lining up a couple per week lately and if it'll keep up it til we get a couple few feet on the groung it could be good.

Also, days like today with the warming chinook like wind in between instead of the deep freeze seems good too.

As long as that TG and some frozen stuff by the ground stays down there in a minimal state I can live with it. That kind of stuff I see at Wolf Creek a lot and we all know about the pack there...

Warm temps can be good if means the snowpack gets melt/freezeish as that seems to rot out slower, like last year.

Wolf Creek - Their avg higher volumes of snow are great for skiing but also ulitmately bridge over even significant hoar. More, More, More

I will say that this weekend, if we get the volumes of snow forecast (8-14"), and any significant wind we are going to see higher avy danger as the ground is an excellent sliding layer, there is some hoar and crust development, and wind slab is all you need. That guy who died off Mines a couple years back was skiing one of these early storms.

**goldenboy** · 10-22-2007, 09:27 AM

Well, it was fun skiing again a couple of days, but in the Elks, we have just enough snow to rot out in the next week or two since there's no snow at all in the forecast. The snow that is on the ground is pretty dense and wet, though, so maybe it will survive and more snow will arrive in time. Fingers crossed.

**khakis** · 10-23-2007, 05:25 PM

Originally Posted by smitchell333

...the ground is an excellent sliding layer, there is some hoar and crust development, and wind slab is all you need.

I've been wondering about this lately...what does it take to get past early-season ground-slide danger? Do sustained cold and a thick insulating snow layer get consolidation down deep? Or is a smooth substrate always going to have a risk of breaking off all the way to the ground?

yeah i know...jong...been out of the game for a few years, taking AIARE 1 in december...

**smitchell333** · 10-23-2007, 09:09 PM

Originally Posted by khakis

I've been wondering about this lately...what does it take to get past early-season ground-slide danger? Do sustained cold and a thick insulating snow layer get consolidation down deep? Or is a smooth substrate always going to have a risk of breaking off all the way to the ground?

I think the answer is basically 1)enough snow that you dont break down into the lower layers and depth hoar development is reduced AND/OR 2) time and melt freeze to consolidate the upper layers enough that you dont penetrate.

The good news is that the hoar is still relatively limited so if you can find places to get out and make turns with out ruining yourself and your skis it can be safe avy wise.

**pechelman** · 10-23-2007, 09:17 PM

on note #2

isnt it an issue if it has time to melt\freeze so that when the water percolates down it dissolves the depth hoar\breaks whatever structure the snow has or surface against the ground?

i noticed you typed that with the assumption of sufficient depth to remove any stress from this interface, but thats not exactly how it is early\late season.

sorry for my brief poorly worded post
i just typed an essay and im hungry and need to shower

**Rontele** · 10-24-2007, 07:19 AM

pechelman, you are a dirtbag.

Forecast doesn't look real promising for snow for the next week or so. After that the models can't really gauge any sort of consensus. Could be dry through the beginning of November.

**pechelman** · 10-24-2007, 08:29 AM

just sayin

its hard to talk about this stuff so im not trying to make anyone look bad or point anyone out as wrong, because its happend to me a lot too on this subject.

there are a lot of assumptions made by the poster, sometimes some information lost in typing and reading said post, and perhaps some things neglected or inferred by the reader that the poster didnt even think about that may or may not be true.

either way, the answer for most of this stuff is really "it depends".