I asked a similar question last winter I think [and am a member of the Ski Club of GB] but the answer wasn't clear, so I'll ask again ...

... The club routinely publishes snow depth figures for the 5 Scottish ski areas at
[www.skiclub.co.uk]

As of this morning, they are [lower slopes, upper slopes] ...

Cairngorm: 10cm, 25cm
Glencoe: 15cm, 45cm
Glenshee: 20cm, 25cm
Lecht: 20cm, 30cm
Nevis: 15cm, 50cm

I'm intrigued to know who makes and supplies these measurements to the SCGB. Clearly, though this winter the precipitation is exceptionally early and heavy (particularly in the west), there is the usual deep drifting and filling ... to the extent that (already) snow depths at Glencoe and Nevis must vary from 0cm to 500cm. Perhaps much more than this already, in some gullies.

So, how are these figures obtained or calculated as averages?



Edited 2 times. Last edit at 11.18hrs Fri 16 Dec 11 by David Goldsmith.

I believe (but the SCGB would not confirm one way or the other in the fairly distant past) that where routine measurements of depth are not regularly taken, that the SCGB uses weather data to estimate snow fall and then predict snowpack depth over time.

Such a strategy would explain how the figures often quoted on the SCGB website for the Scottish Areas can greatly underestimate the depth of cover on the recognised ski runs, where the depth is significantly influenced by windblown accumulations, that arrive on the run often long after the snow stopped falling.

It's not unknown for the Gunbarrel on CairnGorm to fill flat practically overnight 2 weeks after it last snowed, if it's been cold and settled and suddenly you get a Southerly gale coming over the Plateau.

The depth reported for the mid mountain on CairnGorm here, was started in 2010 out of interest to see what actual snow depths at a location compared to reported depths around the web. It's observed on the Cas uptrack, at approximately 2600ft, using a tower for a reference point.

If the same elevation point was used, but from the base of the Gunbarrel, which would require survey tools to measure the drop from the tow track to Gunbarrel surface, no doubt the depth reported would increase considerably - but it would be less reflective of likely depths on the White Lady and M1 for example.

In reality it's basically a bit of fun done out of curiosity. The fact is snow depth data is a worthless tool from a snow reporting perspective here, it doesn't tell you anything useful really, what people need to know is what lifts are open, what runs are skiable and whether to bring powder skis or sharp edges.

I've always felt that if you use - say - 10 permanent poles where the snow lies within proximity of the runs (as you say, alan, a lift tower is good) ... or install a few extra poles where needed ...

... then you average the depths measured from the 10 poles ... you'll get a pretty representative depth measurement.

I can't see how snow depths can be derived from weather data, except maybe for new snow, because there is then a complex calculation to account for snow loss after thaws (particularly if there's heavy rain), and snow compression. It has to be measured as it lies, in its accumulated state.

As for my club, the SCGB, this was a statement on the weekly Snowcast (Ski Club TV) in November 2010:

"What makes the Ski Club's snow reports different is that it's not just automated data from the resorts - we have a team that gathers and checks the information every day. This is how we can deliver unbiased and accurate snow reports to you."

I'll ask the club again if they'll explain the gathering and checking procedure.

In summary, I'd have thought that depth measurements for the upper runs of Glencoe and Nevis - stated as 45cm and 50cm - are very low, looking at the recent photos and videos of the runs.

I've received this response from Alyn Morgan, the SCGB's information manager:

"Thank you for your email. As you rightly point out there are no official measurement depths available for Scotland. We therefore are in regular contact with people at the Scottish resorts to get the best possible data available as well as using other resources that we have at our disposal."

Perhaps that should be translated as: "we make them up"

Just discovered that another website - www.j2ski.com - carries Scottish snow depths. Here they are, for comparison with the SCGB's above:

Cairngorm: 20cm, 30cm
Glencoe: 20cm, 35cm
Glenshee: 20cm, 25cm
Lecht: 20cm, 25cm
Nevis: 20cm, 35cm

So, those depths of 35cm for the upper runs of Glencoe and Nevis are 10cm-15cm less than the SCGB reports, which seemed very low themselves.

If anyone would like to do some 'snow-probing' over the weekend, looking at typical areas of the runs and reporting back, this might be a public service. "We need to get to the bottom of this" [sorry]



Edited 1 times. Last edit at 23.28hrs Fri 16 Dec 11 by David Goldsmith.

David, keep an eye on SAIS snow profiles for the report test sites. Over time, they will give you some idea on the sort of depths that exist on various aspects and elevations in a given season, though test pits done within ski area boundaries are fairly infrequent outwith very wild weather.

At the bottom of each full report page is a link 'View snow profiles related to this report'.

Interesting lead, alan. Had a quick look.

Here are a couple of pits on the western mountains dug by SAIS today:

Glencoe: 900m altitude, 340cm snow depth
Ben Nevis (Observatory Gully): 900m altitude, 240cm snow depth

I think you'd estimated from the weather data that the best of the recent storms had put down at least 40cm 'level depth' snow, so the amplification of that being blown into a gully has got to multiply it many times.

Do we reckon those depths are representative of snow depths on - say the Snowgoose at Nevis or Main Basin at Glencoe?

If you plot the grid reference on a map, should show on this link:

[www.streetmap.co.uk]

The test pit was just on the Flypaper side of the ridge that separates the Spring Run from the Flypaper, the arrow tip is pointing the very edge of the amphitheater like bowl of the Flypaper.

Sorry, clearer at a larger scale:

[www.streetmap.co.uk]

Thanks, alan. So what's to be concluded from this? Is it possible that the snow depths at the top of Glencoe's regular runs are 45cm [SCGB] or 35cm [j2ski] if a 340cm snow pit can be dug in another nearby gully?

This isn't a massive mountain, and obviously Glencoe's various runs are located in the main snow-holding gullies where snow survives longest.

Clearly SAIS will be testing the snow in the slopes most prone to avalanche, but that doesn't necessarily even mean they're looking for slopes with the deepest snow.

I'll raise this in a bit more detail with the SCGB on Monday. SAIS seem to be perfectly clear about how they measure snow depths, so I'll probe a little deeper with the club.



Edited 1 times. Last edit at 12.29hrs Sat 17 Dec 11 by David Goldsmith.

Hi David,

The low SCGB estimates for Scottish snow may help to balance out their normally optimitisc etimates in the Alps !

I wonder what they give for the Lake District today ? 400cm on the lower slopes and 50cm at the top perhaps ?

To update this, the SAIS (SnowSport Avalanche Information Service) - which alan suggested above as an alternative source of info of current snow depths - has published profiles each day since this thread began (16 Dec) based on snow pits of ...

16 Dec 340cm
17 Dec 160cm
18 Dec 240cm
19 Dec 60cm
20 Dec 370cm
21 Dec 70cm

As far as I'm aware, only the figure for the 21 Dec would reflect any thaw.

I've asked the SCGB information dept for further clarification of who supplies the snow depth data and where the measurements are taken.

Just an update on this since both West coast test sites today were taken with in the snowsport areas. At Nevis Range a depth of 400cm was measured on Winger Wall. At Glencoe a depth of 200cm was measured lower down at the very side of the Flypaper Bowl on the edge of the ridge that separates it from the Spring Run.

Snow pits are dug straight down and they might be measuring snow depth perpendicular to the surface of the land. The former is going to be deeper than the latter on steep slopes. What really matters in any case is the average across multiple sample spots. It's no good going digging in drifts.