How to identify icy areas

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How to identify icy areas

Postby sierra_cement » Wed Oct 16, 2019 12:53 pm

A friend of mine stopped skiing after tearing his ACL while skiing an icy surface in Tahoe. I believe that had happened due to a refreeze after rain. I don't want the same to happen to me.

What are the strategies to identify and guess where the icy surfaces? Here is my understanding, please let me know if this is accurate.

- Beginner trails rarely have exposed ice as the slope is not too high. So best to start there to understand the conditions.
- High day time temperatures can produce an icy surface the next morning.
- West facing runs in the morning can have icy slopes. East facing will get soft due if it's sunny.
- Is spring more likely to have icy surfaces? More rain in spring due to higher temperatures?

I mostly plan to ski Tahoe, Utah, Mt. Bachelor for the next few years.
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Re: How to identify icy areas

Postby Tony Crocker » Wed Oct 16, 2019 1:44 pm

sierra_cement wrote:- Beginner trails rarely have exposed ice as the slope is not too high. So best to start there to understand the conditions.

Not really. Lower slopes are more prone to melt/freeze than higher ones, and flat slopes are more prone to melt/freeze than steeper ones with less direct sun
sierra_cement wrote:- High day time temperatures can produce icy surface next morning.

True but other factors such as low altitude, high humidity and high water content snow make snow more prone to turn to hardpack/frozen granular.
sierra_cement wrote:- West facing runs in the morning can have icy slopes. East facing will get soft due if it's sunny.

"Following the sun" around the mountain on warm spring days is a good plan. But there are nuances. How warm is the current day vs. the one that produced the melt/freeze in the first place? To the extent the current day is cooler, some slopes may not soften all day. The first warm day is often really good, as you get the softening part without the freeze before hand.
sierra_cement wrote:- Is spring more likely to have icy surfaces?

On a temporary basis yes. But much of it can be avoided by following the sun if it's warm enough. However, if you get rain when the sun is weak midwinter, you won't get rid of the ensuing hardpack/frozen granular other than by resurfacing with new snow. Manmade snow and grooming can go a long way toward repairing those surfaces but a moderate amount of traffic will scrape it down to the hard subsurface. There's really no substitute for a 1+ foot dump to bring on optimal conditions.
sierra_cement wrote:More rain in spring due to higher temperatures?

In the Northeast rain incidence is least midwinter and very high in the shoulder seasons, November and mid-March and later. But rain vs. snow likelihood on the West Coast is driven more by storm patterns and ocean temperatures. Rain is most likely in November, then in December and least likely in February/March. January and April are in between.

Avoiding unpleasant conditions for ski areas withing driving range is mostly a function of following current weather patterns closely. For Tahoe Bryan Allegretto at OpenSnow is the best resource IMHO.

Once on the hill, watch other skiers while riding chairs. Those are the "guinea pigs" testing snow surfaces you may not be sure about. On questionable slopes Craig Morris at Fernie called them "sacrificial lambs." Listen for "loud turns" on icy surfaces.

Also, part of learning to ski is learning to adapt to conditions. Southern California skiing is nearly perpetual spring, so I learned early on to deal with both hardpack and heavy snow, and to be attuned to chasing the optimal transition period between them.
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Re: How to identify icy areas

Postby sierra_cement » Wed Oct 16, 2019 3:41 pm

Thanks, Tony. A couple of follow-ups:
- More skier traffic -> higher likelihood of icy surface. Especially true on steeper slopes. Correct?
- When do you get a coral reef surface?
- Dust on crust, coral reef is equally dangerous as an icy surface?

Tony Crocker wrote:Not really. Lower slopes are more prone to melt/freeze than higher ones, and flat slopes are more prone to melt/freeze than steeper ones with less direct sun

I got this completely wrong. Higher elevation -> brighter sun due to less atmosphere. So a beginner slope high on the mountain will still be icy if it is sunny.

But there are nuances. How warm is the current day vs. the one that produced the melt/freeze in the first place? To the extent the current day is cooler, some slopes may not soften all day. The first warm day is often really good, as you get the softening part without the freeze beforehand.

I don't think I understand this. What is the importance of softening without the freeze?

In the Northeast rain incidence is the least midwinter and very high in the shoulder seasons, November and mid-March and later.

No plans to visit North-east for skiing but good to know.

But rain vs. snow likelihood on the West Coast is driven more by storm patterns and ocean temperatures. Rain is most likely in November, then in December and least likely in February/March. January and April are in between.

Temperatures also follow a weird pattern here. I remember a 55 degree ski day at Northstar in January.

What about Utah? I believe rain is not likely in the Cottonwoods due to their higher elevation. What about the other areas like Park City, Powder Mountain?

Avoiding unpleasant conditions for ski areas withing driving range is mostly a function of following current weather patterns closely. For Tahoe Bryan Allegretto at OpenSnow is the best resource IMHO.

Thanks, I will start following this.

Once on the hill, watch other skiers while riding chairs. Those are the "guinea pigs" testing snow surfaces you may not be sure about. On questionable slopes Craig Morris at Fernie called them "sacrificial lambs." Listen for "loud turns" on icy surfaces.

If unsure about iciness, I will only get on that lift if it allows downloading or has a cat track down. A flat icy slope is less scary than a steep one.

I believe these are the mountains with high elevation beginner/lower intermediate terrain in Tahoe:
Heavenly: good intermediate terrain at high elevation, no beginner terrain at higher elevation.
Mt. Rose: good beginner and intermediate at higher elevation (8200)
Kirkwood: low on the mountain but still high elevation (7800)
Squaw: beginner terrain @ 8200. Some intermediate terrain up high.
Alpine: some intermediate at higher elevation but it ends at low elevation.

Others don't have beginner/intermediate terrain at high elevation.

*** Utah ***
Cottonwoods: the base elevation is high by Tahoe standards but all beginner terrain is low on the mountain.
Park City: beginner terrain low (same as Northstar). Some intermediate terrain higher and north-facing (Silverlode).
Canyons: higher beginner/intermediate terrain above Red Pine. North facing intermediate terrain at Iron Mountain/Dreamscape/Daycatcher.
Deer Valley: don't know
Powder mountain: some beginner terrain above 8k as per the trail map.
Snowbasin: not much beginner/low intermediate terrain.
Beaver Mountain: the whole mountain is lower elevation than others so best for mid-season only.
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Re: How to identify icy areas

Postby Tony Crocker » Thu Oct 17, 2019 1:38 pm

"Coral reef" usually refers to an ungroomed slope of irregular snow that has melt/frozen. As far as dust on crust is concerned, the steeper and less smooth the slope, the more new snow is required to be able to make turns in the new snow as opposed to being on the old subsurface. That's why I refer to days with say 3-6 inches new snow as "low angle powder days." If you want to ski powder on those days, look for intermediate not advanced terrain. It's even better if the subsurface was groomed before the new snow. Higher speeds and longer radius turns are also helpful to minimize contact with the old subsurface.

sierra_cement wrote:- More skier traffic -> higher likelihood of icy surface. Especially true on steeper slopes. Correct?

Yes, but this is the scenario where manmade snow tends to be more difficult than natural snow, especially if the natural snow fell as low water content. Intermediate trails in Colorado can take a fairly high traffic load and be more resistant to icing IF they are predominantly natural snow. In mid-season Sun Valley and perhaps a few places in Colorado will deliberately make 8-10% water content "gunpowder" to top off groomed trails with snow more similar to natural snow.

sierra_cement wrote: I got this completely wrong. Higher elevation -> brighter sun due to less atmosphere. So a beginner slope high on the mountain will still be icy if it is sunny.

Higher elevation means less dense air, makes it more difficult to transmit the temperature from that air into the snow. If the air has a lot of water vapor in it (high humidity), that makes it easier to transmit the temperature from that air into the snow. A high elevation beginner slope is more likely to melt/freeze in the first place than a lower one and the lower melt/freeze may be more thorough/severe. But once the melt/freeze has occurred over both slopes, the higher slope will take longer to soften.

sierra_cement wrote:Temperatures also follow a weird pattern here. I remember a 55 degree ski day at Northstar in January.
55 degrees in January is still less likely to produce as severe a melt/freeze as 55 degrees in March due to lower sun angle. And even 55 degrees in March may not produce a melt/freeze on a high altitude and steep north face.

sierra_cement wrote:What about Utah? I believe rain is not likely in the Cottonwoods due to their higher elevation. What about the other areas like Park City, Powder Mountain?

I think rain is still quite rare in those places. But there are multiple reasons the snow is so much better in the Cottonwoods than elsewhere in Utah.
1) The obvious is ~50% more snowfall to refresh surfaces.
2) The other places therefore have more snowmaking dependence so that subsurface is more often evident. Powder Mt. is nearly all natural, but that means its lowest Paradise chair can take awhile to open in early season.
3) Higher altitude in the Cottonwoods
4) Higher proportion of north facing in the Cottonwoods. The steepness of much of that north facing at Alta/Snowbird adds further to this advantage.
Virtually every factor related to snow conditions favors the Cottonwoods over the other Utah areas, so the cumulative difference can be huge, especially in the shoulder seasons.

You impression of specific areas is overall accurate. From what you have said about your wife, June Mt. would be nirvana to her. The Silverado run there is true green, 2 1/2 miles long starting from 10,000 feet. And June is very quiet as it's overshadowed by nearby Mammoth. Both are on the Ikon Pass.
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Re: How to identify icy areas

Postby ShiftyRider » Thu Oct 17, 2019 7:17 pm

Re the subject just go to Mt Baldy, hop aboard Chair 3, and look around. If ShiftyRider is nowhere to be found on the descent, it means that Emile's and Liftline are too icy...
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Re: How to identify icy areas

Postby sierra_cement » Thu Oct 17, 2019 9:21 pm

ShiftyRider wrote:Re the subject just go to Mt Baldy, hop aboard Chair 3, and look around. If ShiftyRider is nowhere to be found on the descent, it means that Emile's and Liftline are too icy...


haha.. love it.
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Re: How to identify icy areas

Postby sierra_cement » Thu Oct 17, 2019 9:37 pm

Tony Crocker wrote:You impression of specific areas is overall accurate. From what you have said about your wife, June Mt. would be nirvana to her. The Silverado run there is true green, 2 1/2 miles long starting from 10,000 feet. And June is very quiet as it's overshadowed by nearby Mammoth. Both are on the Ikon Pass.


Thanks Tony. Hope we can make it to June this time. We will be skiing more at Mt. Rose this time.
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Re: How to identify icy areas

Postby tseeb » Fri Oct 18, 2019 9:20 am

sierra_cement wrote:*** Utah ***
Cottonwoods: the base elevation is high by Tahoe standards but all beginner terrain is low on the mountain.
In your other thread, I pointed out that Brighton in Big Cottonwood Canyon has a base of 8755' and top to bottom beginner runs off two of their chairs to the top (over 10K'). Snake Creek is N-facing and heavily treed so snow not affected much by sun. Milly is NE-facing and lone beginner run starts on N-facing slope then wraps around to E-facing. But not sure how appropriate either of these are for a true beginner.

Tony Crocker wrote:A high elevation beginner slope is more likely to melt/freeze in the first place than a lower one and the lower melt/freeze may be more thorough/severe. But once the melt/freeze has occurred over both slopes, the higher slope will take longer to soften.
While I agree with most of your comments, I have to wonder if "A high elevation beginner slope is more likely to melt/freeze in the first place than a lower one" is a mistake. Given similar exposure and usual altitude/temperature correlation, it seems like the opposite is true.

If your only experience is at Squaw, where beginner terrain is at both bottom and high on mountain, but bottom is heavily forested and shaded and N-facing while top is very lightly treed and is mostly S and E-facing, and there are often temperature inversion where bottom is (sometimes much) cooler than beginner area at top in AM, even the comment "once the melt/freeze has occurred over both slopes, the higher slope will take longer to soften" can be questioned.
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Re: How to identify icy areas

Postby Tony Crocker » Fri Oct 18, 2019 12:19 pm

My comment should have been prefaced, "other factors being the same." Worse exposure can easily be an overriding factor. As for Squaw, beginner terrain at its base must be microscopic. I can't say I've ever noticed it.
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Re: How to identify icy areas

Postby sierra_cement » Fri Oct 18, 2019 1:03 pm

Thanks Tseeb, great point about Squaw. Definitely relevant as we plan to go to Squaw a few times this season. But most likely more Mt. Rose than Squaw. I think Mt. Rose will be better place to learn than Squaw.

tseeb wrote:In your other thread, I pointed out that Brighton in Big Cottonwood Canyon has a base of 8755' and top to bottom beginner runs off two of their chairs to the top (over 10K'). Snake Creek is N-facing and heavily treed so snow not affected much by sun. Milly is NE-facing and lone beginner run starts on N-facing slope then wraps around to E-facing. But not sure how appropriate either of these are for a true beginner.

I checked the trail map. Yes, there are runs off Snake Creek and Milly. The access to Milly is via Majestic. And the access trail is rated blue. Main street off Milly is accessed by Backdoor trail which is rated blue. Hopefully my wife is good enough by April to do a short blue section. I used to be terrified of the short steep sections during my first 10 ski days. I will only take her there if she is feeling confident. Brighton looks like a great spot for April. Sleep in SLC at lower elevation and still enjoy the good snow, hopefully with fewer crowds than main season.


Tony Crocker wrote:My comment should have been prefaced, "other factors being the same." Worse exposure can easily be an overriding factor. As for Squaw, beginner terrain at its base must be microscopic. I can't say I've ever noticed it.


I have been on the lower beginner trail called Pioneer off First Venture lift. I liked it. I think it was my 3rd ski day. It is off to the side on it's own and I don't believe I saw much expert traffic comingled. But it is very short and mostly for true beginners in the first few days on skis. The runs at top of the mountain are longer and fun. I do remember it was a bit of walk from the First Venture lift to the funitel.

Do any of the east facing runs that have softened earlier in the day freeze up in the afternoon? I think maybe the contact with cold snow underneath and no heating from the sun could freeze them up.
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Re: How to identify icy areas

Postby tseeb » Fri Oct 18, 2019 3:49 pm

Tony, I still don't understand how "high elevation beginner slope is more likely to melt/freeze in the first place than a lower one". Since the first part of melt/freeze is melt and that is less likely to occur at high elevation due to lower temps and as you said "Higher elevation means less dense air, makes it more difficult to transmit the temperature from that air into the snow", won't there be less melt/freeze since there is less melt?

And sierra_cement, I see green Snake Creek Access also trail covers part of the route from top of Majestic to Snake Creek lift. But I'm not familiar enough with the area to know if that route is true beginner or if you can easily cross Hawkeye to get to green Thunder Road which also gets you to Snake Creek lift. It does look like there are two long greens from the top of Snake Creek and it seems like it would make sense to have an easier way to get to bottom of lift from top of Majestic so beginners can ski those. If you do get there, the views off the back are beautiful. As far as getting to Milly, the problem with the access trail is there is an X-intersection between Majestic Access and Milly Access where you need to carry speed to avoid having to walk trail along edge of parking lot. It may be easier to walk across parking lot or take what would be very short shuttle if one goes that way.
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Re: How to identify icy areas

Postby sierra_cement » Fri Oct 18, 2019 4:14 pm

tseeb wrote:Tony, I still don't understand how "high elevation beginner slope is more likely to melt/freeze in the first place than a lower one". Since the first part of melt/freeze is melt and that is less likely to occur at high elevation due to lower temps and as you said "Higher elevation means less dense air, makes it more difficult to transmit the temperature from that air into the snow", won't there be less melt/freeze since there is less melt?

All things being equal (which is rarely true when it comes to ski slopes), a higher elevation slope will get more intense sun due to less atmosphere. The cold temperature at higher elevation is not able to keep the snow cold because there is less medium for heat transfer. So the impact of more intense sun is higher than the cooling effect of the cold air. So more quicker to melt. At least that's how I understand it. You guys probably have more practical knowledge.


And sierra_cement, I see green Snake Creek Access also trail covers part of the route from top of Majestic to Snake Creek lift. But I'm not familiar enough with the area to know if that route is true beginner or if you can easily cross Hawkeye to get to green Thunder Road which also gets you to Snake Creek lift. It does look like there are two long greens from the top of Snake Creek and it seems like it would make sense to have an easier way to get to bottom of lift from top of Majestic so beginners can ski those. If you do get there, the views off the back are beautiful. As far as getting to Milly, the problem with the access trail is there is an X-intersection between Majestic Access and Milly Access where you need to carry speed to avoid having to walk trail along edge of parking lot. It may be easier to walk across parking lot or take what would be very short shuttle if one goes that way.

Thanks.. I will do a few runs myself before getting the family on those lifts. Let's hope I get there this season. If not this season, it's highly likely we will go to Brighton Solitude sometime in April in future years. Our school district usually has 2nd week of April off.
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Re: How to identify icy areas

Postby Tony Crocker » Sat Oct 19, 2019 12:28 pm

tseeb wrote:I have to wonder if "A high elevation beginner slope is more likely to melt/freeze in the first place than a lower one" is a mistake.
Yes a mistake, low elevation is more likely to melt/freeze.

sierra_cement wrote:All things being equal (which is rarely true when it comes to ski slopes), a higher elevation slope will get more intense sun due to less atmosphere. The cold temperature at higher elevation is not able to keep the snow cold because there is less medium for heat transfer. So the impact of more intense sun is higher than the cooling effect of the cold air. So more quicker to melt. At least that's how I understand it. You guys probably have more practical knowledge.

This is not true, and I'm sorry my misquote above added to the confusion. The effect of the higher thin atmosphere is that it is a better insulator than denser air and especially high humidity air. That's why frigid temperatures of zero F or below feel colder in the Northeast than in Colorado or Alberta.

Combine that with the higher elevation being cooler at the average rate of 4F per 1,000 of elevation and there is no question that winter snow lasts longer the higher you go most of the time. Midwinter temperature inversions are an exception, but in those situations the effect is generally not to melt the higher snow (the sun angle is still weak) but mainly to better preserve the lower snow.

For intermediate and better skiers, exposure has a more dramatic impact than altitude in spring, especially within a North American ski area where the bulk of terrain is within a 2,000 foot range. But I was impressed with the absolute effect of altitude at the highest elevations in Colorado in April 2011. East facing slopes at Breck and Loveland over 11,500 feet were still retaining winter snow. Another absolute altitude effect I see is rain resistance. An overall good rule of thumb is that there is a snow preservation tradeoff of about 1,000 feet in altitude for 4 degrees of latitude. For spring melt/freezes I think this rule works well, but for rain incidence Mammoth at 11,000 feet still gets almost no rain vs. maybe a couple of times a season at Bachelor at 9,000 or Whistler at 7,000.
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Re: How to identify icy areas

Postby tseeb » Mon Oct 21, 2019 5:34 pm

I think some of sierra_cement's confusion over "a higher elevation slope will get more intense sun due to less atmosphere" is he is confusing the effect of the sun on his skin vs. snow. The higher elevation/less atmosphere means less UV gets blocked which means sun's effect on our skin is more intense, but as Tony Crocker says sun does not melt snow at higher elevation more easily.
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