Wednesday, March 18, 2009

That was the winter that was—how to quantify ski conditions

Recently, we explored the weather of the now-seemingly-over winter of 2008-2009. Today, we'll look in to how the skiing went, and how it measures up against recent years. With the weather, it was rather easy. First of all, there are numbers. There's data going back nearly two centuries. So it's not very qualitative. Second of all, some folks have done a lot of work documenting the weather. Ski conditions, on the other hand, are a little harder to quantify. We'll set up the qualifications for different levels of ski season quality (excellent, good, fair, poor) today, and explore the current season, and recent past seasons, later this week.

One way to do this is to count skiable days. But where do you count them, and how? Do you count days you could ski on the Como Glacier (quite a few—it probably still has snow on it)? Or days you could use your best skis at Murphy (not quite as many days, but it is a bit more fun)? And if we are going to rate ski seasons (as I am about to attempt to do), we need to establish some sort of criteria. We'll figure out how to decide whether it is an excellent, good, fair or poor season for skiing. So, what makes a good snow year?

Well, jumping beyond trail conditions at large, we can focus on three trails at three times: The City of Lakes Loppet Course (when it is held), the Mora Vasaloppet course when it is held, and the Birkie. These are entirely subjective: three points in time in three disparate locations. They do, however, account for the three largest long races anywhere near the Twin Cities. In addition, they are the only local (under three hours drive) snow-on-the-street finishes—with cheering crowds lining the course. They occur from late January to late February, generally the peak of most local racing (although there are many fine races earlier on), and when we really want snow on the ground. I'd be hard pressed to call it a "good snow year" if one (or more) of these events is shortened, "laked" or canceled. Plus, they traverse a diverse set of terrain, and they are usually rather indicative of local trail conditions.

Thus, these races will be used to assess ski seasons as follows:
• For a ski season to be excellent, all races must be held in their entirety (with the minor exception that the City of Lakes may be shortened by a couple kilometers since it is the furthest south of any major races and most prone to melting—if a couple k on the front nine are shaved off, it still qualifies).
• For a good snow year, at least two races must be fully held, and the third can not be canceled, it can only be shortened (due to snow, not cold temperatures, which do not represent the snow conditons) or "laked."
• If more than one event is shortened, or one is canceled, a season can be ranked only as high as fair, and
• If all three are shortened, or more than one is canceled, only a poor rating for the season will suffice.

Beyond the races, we begin to analyse snow conditions. When we looked at the year in weather, we looked some at snow depth. But ski conditions are based not only on snow depth, but on the temperature (ice, slush, &c.) and, of course, on grooming. What good is six inches of snow pack if it is topped with an impenetrable layer of glare ice? And what of the differences across the area? Sometimes there's good skiing at Murphy and Lebanon with brown grass at Elm Creek and Elk River. Sometimes Woodland Trails have good conditions and everyone else is on man-made snow. At times the whole Metro is very white, but only some areas have good enough grooming to merit good conditions. Wouldn't it be nice if there were a treasure trove of ski trail observations from across the Twin Cities going back several years?

Of course, I am referring to's "First Hand Trail Reports." Thanks to Bruce and his archiving, we can go back towards the start of the internet and compare conditions across the area each day of the winter—from the first "fast grass" to the last melting slush at Woodland Trails. For the purposes of this analysis, the "Metro" will stretch across the seven county region, and poke in to Sherburne to include the trails in Elk River, which often prolong the local ski season on their own.

Now, how do we count skiable days? Well, based on the reports on Skinnyski, I've devised two levels of skiing. One is "poor to fair." For a day to be counted under this criterion, somewhere in the Metro (other than a lake or manmade snow) needs to be at least somewhat skiable. This can include "fast grass" or crust skiing, but somewhere there must be the ability that day to strap on a pair of rock skis and glide. That is counted as a poor-to-fair day. The other criterion is "good to excellent." For this to be in play, somewhere between Murphy and Elk River needs to be skiable with good skis (excellent or very good) or at least two locations need to be reporting "good" conditions—skiable on at least "B" skis. If these criteria are not met, it is counted as a fair-to-poor day.

Once the days are counted, we can quantify a season:
• An "excellent" season must have at least 100 days of skiing, with at least 75 "good to excellent"
• A "good" season must have at least 75 days of skiing, with at least 50 "good to excellent." If a season has more than 100 days of skiing, only 40 need to be "good to excelent"
• A "fair" season requires at least 50 days of skiing, with at least 35 rated "good to excellent." A season with 20-30 days of "good to excellent" skiing can qualify for fair if it had at least 75 days of skiing overall.
• If a season does not meet any of these criteria, it is rated as a "poor" ski season.

Since this is already quite subjective, I'll throw in a few more criteria:
• For a season to be rated "excellent" there must be at least 20 days of skiing in December, January and February. March skiing is great, but it's not the same when the skiing is after all the races.
• For a season to be rated "good" there must be at least 20 days of skiing in at least two of the months of December, January and February.
• For a season to be rated "excellent," Murphy-Hanrahan, the most notorious of the "needs a lot of snow to open" venues, must be open and "good to excellent" in at least three separate calendar months. For a "good" season, two are required.
• No season may be rated "good" or higher unless there was at least ten days of skiing before January 1. What good is late snow when you are rollerskiing on Christmas?
• No season may be rated as "excellent" when a major race (such as the Bear Chase, the Noque, the Pepsi, the Gov Cup, any major Birkie Trail event, the Minnesota High School Championships, Nationals or JOs, if they are held in the Upper Midwest, &c.) is canceled due to lack of snow. If two are canceled, a season will not be rated "good."

Finally, ski seasons will be rated at a certain level only if all of the criteria for that level are met. Later this week we'll rate this season, and past seasons back to 2002-2003, with some nifty charts as well.

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