# Depth Hoar Questions



## AcroPhile (Dec 3, 2010)

Ok, there has been a bit of discussion about this in relation to early season snow on the Colorado Conditions thread, so lets talk about depth hoar. 

If I understand it correctly, depth hoar forms when we get some early season snow and then it doesn't snow for a while. It happens on a thin snowpack where a temperature gradient forms in the snow between the warm ground and cold air temp. A thicker snowpack weakens the temperature gradient, therefore creating unfavorable conditions for the formation of depth hoar. 

Everyone seems to think the October snow is going to mess up the snowpack for most of the upcoming season. Obviously, getting a big snowstorm or two then a month of nothing is going to be bad news in terms of a persistent weak layer. 

My question is, what's wrong with October snow as long it keeps snowing? If we get a consistent snowfall throughout this month and next without periods of drought, wouldn't we avoid the depth hoar problem? And, how often does it need to snow to avoid formation of depth hoar? For instance, in Colorado lately, the higher elevations have been getting snow at least once a week. I think that's pretty good, snow wise. Most others, think it's bad news.


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## ETM (Aug 11, 2009)

You kind of answered most of your own questions there and all your information is correct.

If it does regularly snow then the problem of a large temperature gradient promoting depth hoar is not such a concern. You could however argue that the ground will be warmer than it would have been in 2 months time thus promoting a large temperature gradient. 
You might be correct in saying the higher slopes will have no problem, but there might be a depth hoar layer that forms in relation to altitude like a big ring around the mountain.

All of this is purely speculation though, the best thing you can do is start keeping a record of the snowpack if possible so you dont blindly walk into harms way. 
It will be a very interesting season in regards to snowpack for you guys thats for sure.


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## killclimbz (Aug 10, 2007)

^^^Thanks ETM. 

Yes early October snows fuck us. Generally because it doesn't snow much after a decent storm and the warmer ground doesn't help with gradient. We are stuck with the snow being exposed to the warm ground, but I have to think that in the higher elevations, it has mostly cooled off by now. So we are getting a storm over the next 24-48 hours. Hell yeah! Hopefully we get another one in a few days and so on. The quicker the snow pack gets deep the better.

So will deth hoar form? Yes. It is *always* a problem here. How much of the problem is the question. Last year thick layers of depth hoar and some persistent deep slabs created some dangerous conditions as we all saw. The depth hoar was close to 3ft of it in spots to the ground. Hopefully this year it is less than a foot. 

I haven't gotten out yet, there is some stuff to get done. I might shoot for Sunday this weekend. I'd like to get out there and see what this early season snow is doing for sure.


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## snowklinger (Aug 30, 2011)

killclimbz said:


> ^^^Thanks ETM.
> 
> Yes early October snows fuck us. Generally because it doesn't snow much after a decent storm and the warmer ground doesn't help with gradient. We are stuck with the snow being exposed to the warm ground, but I have to think that in the higher elevations, it has mostly cooled off by now. So we are getting a storm over the next 24-48 hours. Hell yeah! Hopefully we get another one in a few days and so on. The quicker the snow pack gets deep the better.
> 
> ...


Yea looks like there might even be moist flow behind the storm for a few days. :yahoo:

We should be shredding next week!


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## killclimbz (Aug 10, 2007)

People are shredding already. There is enough snow out there now to get it done.


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## snowklinger (Aug 30, 2011)

killclimbz said:


> People are shredding already. There is enough snow out there now to get it done.


Yea but I'm holding out for WROD!!!


...that and I may be seriously injured....went for a hike 2 weeks ago and my knee is FUCKED!


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## killclimbz (Aug 10, 2007)

snowklinger said:


> Yea but I'm holding out for WROD!!!
> 
> 
> ...that and I may be seriously injured....went for a hike 2 weeks ago and my knee is FUCKED!


Ah dude, I hope not. I'd get that sonofabitch looked at right away. I know everyone gets excited for this time of year. The thing is almost every year, March, April, and May are the best time of the year. Last year was certainly the case by far. At least find out what you did to weigh your options. 

Fingers crossed for you. Thought I might see you on a split this season.


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## mhaas (Nov 25, 2007)

Do you guys consider early season depth hoar to be any more dangerous than any other persistent hazard such as a rain crust, a buried weak layer or even mid winter depth hoar? Just curious.

The storms have been just skimming northern Utah but each one has added up to around a foot. But luckily (?) most of it has melted once it warms up during the week, except for the high NF peaks.


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## karkis (Jan 8, 2013)

AcroPhile said:


> ... depth hoar forms when we get some early season snow and then it doesn't snow for a while. It happens on a thin snowpack where a temperature gradient forms in the snow between the warm ground and cold air temp. A thicker snowpack weakens the temperature gradient, therefore creating unfavorable conditions for the formation of depth hoar.
> ... what's wrong with October snow as long it keeps snowing? If we get a consistent snowfall throughout this month and next without periods of drought, wouldn't we avoid the depth hoar problem? And, how often does it need to snow to avoid formation of depth hoar? For instance, in Colorado lately, the higher elevations have been getting snow at least once a week. I think that's pretty good, snow wise. Most others, think it's bad news.


sounds like you have a pretty good handle on it but for clarity and for other readers you might note that drought doesn't necessarily create a steep temp grade but if you're in CO it will tend to be quite cold thru periods of high pressure during the winter. That's your problem, CO is exposed to a continental climate which will be reliably cold and dry thru the winter. If you are so lucky to have an exceptional wet / deep season, keep in mind that wind distribution will create areas of shallow snow regardless of the average coverage.



mhaas said:


> Do you guys consider early season depth hoar to be any more dangerous than any other persistent hazard such as a rain crust, a buried weak layer or even mid winter depth hoar? Just curious.


more dangerous? ... i'm not sure if you mean hazardous? 
if you're talking hazard, consider that depth hoar from early season, for the reasons noted above, tends to be widespread and deep which contribute to it being unpredictable and consequential, and hard to manage exposure to it.
Faceting later in winter tends to be more localized to shallow spots, rain crusts tend to occur at lower elevations, surface hoar tends to grow most in specific locations, sun crusts on solar aspects.... often you can work around / limit exposure to those hazards.

If you really do mean 'dangerous', and given that continental snowpacks are historically more dangerous for skiing (fatalities per user numbers) and deep slab on depth hoar is a big part of that stat, then yah its probs the most dangerous beast.


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## wrathfuldeity (Oct 5, 2007)

killclimbz said:


> Last year thick layers of depth hoar and some persistent deep slabs created some dangerous conditions as we all saw. The depth hoar was close to 3ft of it in spots to the ground. Hopefully this year it is less than a foot.
> 
> 
> > So are you saying that you have a 3' hoar layer on the ground that's buried?....that's crazy...I could only imagine if you felt that womp...you'd be shittin da pants.


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## killclimbz (Aug 10, 2007)

Yep, we did. With a hard slab on top. Not everywhere of course Spatial variability an all. Find a spot where that slab was weak though and bad things could happen. As we all saw unfortunately.


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