May 9, 2012

Snow in the Cascades

Filed under: Hiking, North Cascades, Snowpack, Weather — geezerwriter @ 4:39 pm

This morning as I was sitting at my computer trying to avoid going to the gym, I recalled having a short conversation at my meeting last Sunday about Snotels. These are remote automated weather stations that have been built at various places in the mountains by the Natural Resources Conservation Service, an arm of the USDA (Department of Agriculture). I had run across them in the past while poking around on my favorite weather website Weather Underground, Inc, but I never knew if they were accurate or reliable – I knew they reported snow depth, for instance, but were they measuring the actual snow depth at the moment or the total amount that had fallen or the water equivalent or what?

The man I spoke to at the American Alps meeting, a long-time employee at North Cascades National Park, was saying that they do measure actual snow depth as well as water content and are accurate enough that they are used by Seattle City Light, the Seattle utility that operates the three hydroelectric generating stations at the three big dams on the Skagit River along North Cascades Highway (SR 20).

And then this morning as I scrolled down through my local weather underground page I noticed a clutch of links to snotels in the area, two along the Middle Fork of the Nooksack River (near Lookout Mountain, called MF Nooksack, and Elbow Lake, resp.) and one on the North Fork (off Wells Creek Road). Those locations are approximate since the websites only give the latitude and longitude down to degrees and minutes, and a minute of latitude is more than a mile – I presume that don’t want unauthorized riff-raff (like me) to be able to find them. [I just had a bright idea of how to narrow the search but I’ll keep that to myself, for now.)

Anyways, the nice people at NRCS not only display current data and complete historical data for the entire lifetime of the snotel (10-20 years) in neat tables on your browser but they also package it in a machine-readable format (CSV) that can be imported into a spreadsheet application. Once there it can be manipulated and charted in all sorts of ways.

The motivation for this is that our hiking season was almost wiped out last year by the extraordinary La Nina snowfall. And we have now had a rare back-to-back La Nina this year, with near record snow depths at the Mount Baker Ski Area – great for skiers, not so much for hikers. We will be setting our July-September schedule in a few weeks and it would be nice to get an idea of when we can go where. So the first thing I did was download the data for the last two years at the MF Nooksack and Wells Creek locations, which I chose because they are in the areas where we hike in the summer and are at the sort of elevations that we hope to reach – 4900 feet and 4030 feet, respectively.

Snow Depth 2010-12 at MF Nooksack (4900′)
and Wells Creek (4030′)

The black line (on all graphs) is the current “water year”, starting on October 1, 2011. The first thing that struck me on the MF chart is the flat-topped area where it seems to be bouncing off the 200 inch line – I suspected that this might be some sort of physical limitation on the equipment. But the WC chart shows a very similar shape (at a lower level, to go with the lower elevation) so I don’t think it is an artifact. Notice also how it tracks with our experience at sea level – it is almost flat in December (which was unusually dry) with barely enough new snow to keep up with the natural settling and compaction, and then takes off after the New Year, with a monster spike in Feb and Mar, which were especially wet in town, too.

The encouraging thing is that the maximum snow depth was higher and earlier this year. Last year’s green line doesn’t peak until mid April and then hangs like Michael Jordan on a dunk well into May. I love the way this year’s line is already below last year’s – and the current warm sunny weather can’t hurt.

To get more of a context I went back and downloaded the 2010 data (the brownish line), which I remember as a more typical year. But was it really? The only way to know is to get more data…

MF Nooksack data for the years 2003 to 2012

So I fetched the entire history of the MF Nooksack snotel which went into service on October 10, 2003. Most years had some missing data (and some had a lot) so I smoothed over most of them, except 2008 (purple) which had such huge gaps that it would just be wild guessing.

This was even more encouraging – with the exception of that big hump in March we are moving close to where all but two recent years are clumped together.

On more picture: I averaged the years from 2003 to 2010 (with the exception of 2005 which is an obvious outlier on the low side) and graphed it with last year and this year, which gives a cleaner picture:

2012 and 2011 vs. the average of seven prior years

So where’s the beef? We are still well above average but well below last year. That little zag in the black line tracks with the damp, chilly weather which has been all too apparent on our recent hikes – without that we would be on a trajectory more likely to join the red line than the green one. So I think it is not too late for some warm, clear weather to rescue this year’s summer hiking season.


1 Comment »

  1. This is very interesting, Al! And encouraging. See you tomorrow for a nice hike in the sunshine…

    Comment by DJan — May 9, 2012 @ 7:34 pm

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