That was the winter that was—weather

In the space of about 36 hours last week, we went from -4 to 50, and two days later we were close to 70. It melted all the snow this side of Duluth, it seems, and, looking at the weather charts for the next couple weeks to April (have we skied in April? Yeah, but it melts real quick), has pretty much put an end to the ski season. Today, I'll tackle the numbers, later I'll look at the ski season.

So how did it stack up? How does it compare to last year, and previous years. Was it warmer or colder? Was the snow better or worse? How was the skiing and grooming?

Well, there are a lot of ways to answer. First, we can look at the temperatures and snow (skiing will come later). "Meteorological Winter" runs from December to February—for which records are kept. March counts as spring. This coincides rather nicely with local ski season—there are some races in March but the big ones are done and the races are generally up north. Here's how it looks:

Month	Avg. High	Avg. Low	Mean	Max	Min	Hi >32	Lo <0
Dec.	23	4	13.5 (-5.2)	41	-13	6	12
Jan.	16.8	-0.2	8.3 (-4.8)	46	-22	1	15
Feb.	29.1	12.4	20.8 (+0.7)	47	-5	13	4

A few more tidbits: snowfall was about normal (17, 8 and 11 inches) as were below zero temperatures—about 30 for the winter. There were ten days below -10, and two below -20, the first time in five years. We had a month below freezing (December 30-January 30) and almost a calendar month until the temperature skied to 46 on the afternoon of the last day of January. We were running about five degrees colder than normal, February was about average.

The coldest day of the winter was January 15, which actually fell midweek and not during a race—what are the chances. Up north was down near -40; at the airport the high was -6, the low -22, meaning for the day it was 25 degrees below average. A lot of the 'burbs went to -30 or colder. March 11, however, with a high of 8 and a low of -3, was 27 degrees below average. The warmest day, and the only day not to fall below freezing, was during the mid-February, snow-eating meltdown when the high was 47 and low was 35, 23 degrees above normal. That was a bummer—at least it was post-Mora and post-City of Lakes and Birkie was pretty much spared.

Now, on to the meteorological, numerological and chartological fun. A guy called Charles Fisk has a great website chronicling Twin Cities weather back to the '20s. The 1820s. I'm not going to link his whole site—though I could—but he has taken a ton of data and presented it in great charts. For instance, here's the month of January, in temperature.

But then it gets cool. For this winter he has charted snowfall, against the average snowfall. It'll make more sense with a chart:
Okay, that's pretty cool. And he has charts going back to 1884 (for snow), for the year, with snowfall, snow depth, temperature and all else. Here's 2008, for example. And then he has some outrageously awesome charts, like this one, showing average temperature over the whole year, by hour. Uh, amazing? I could spend all day at this site.
No wonder I love early may—60s and dry. If that's not cool enough, he has charts about wind speeds and directions and even thunderstorm probabilities (most frequent just before dawn in July fwiw).

Anyway, what can we deduce from all this information? Well, it was a pretty normal winter. It was a little colder early on, and then normalised some. The snow never got deep, but it's not terribly frequent to have deep snow in the Twin Cities. Look at the average snow depths by day for Minneapolis. The median from Mid-January to Mid-February is about five inches of depth—which is about what we had this winter. And before New Years it is significantly less. So, I got to thinking, when did we build a real "base" of snow? When did we have a good, deep layer of snow on the ground—a foot or more—in January or February. It seems abnormal not to have it, although it is actually an aberration. The last time the snow depth was more than a foot in January or February for more than a couple days was in 2001, a good snow year; and before that 1997. Before that, you have to go back to even years in the early '08s: 1986, 1984 and 1982. Before that were six years from 1969, '70, '71 and '72, 1975 and 1979. Before that, it happened one other time in each the 1960s, 1950s, 1940s, and 1930s. So people remembering the big winters remember a seventeen year period from 1969 to 1986—since the advent of skating there have been two winters with real "base building."

What I mean by base building, is snow maps like (and these are from the Minnesota Climate Working Group at the U, going back to the mid-90s):
That's March 1, 2001. Most of Minnesota had had a foot of snow or more on the ground for a month, and more than 18 inches at the end of the month. I wasn't around, but that looks awesome. The best we mustered this year was mid-January, when most of the state had a foot. Not too shabby.

A couple more data points: A nice article from skinnyski.com (PDF) shows that the 1960s to 1980s were higher than average in snowfall but that we actually seem to be getting a bit more snow compared to the first half of the century(see pages six and seven). From Fisk's site, again comes:
(click to enlarge). Again, it shows the heyday of snow in the Twin Cities from about 1970-1985, but also it looks like snowfall has been increasing slightly. Does this mean the snow sticks around more? No, likely not—warming temperatures may preclude that, but they may well cancel each other out.

And, we might well be due for a nice, good winter with a foot and a half of snow on the ground where one warm spell doesn't kill the snow, as they seem to come once a decade or so (save for the '70s and '80s). Of course, we have snow-making now (and Wirth will probably get better at, you know, making enough snow) which helps, too. We paid dearly from 2001 to 2007—we'll explore that soon—but have done rather well this year and last, and hopefully will do better going forwards.

And stay tuned for a rough analysis, using Skinnyski.com trail reports, of conditions for every day back to 2002 (when Bruce's site started archiving).

(Oh, and take this all with a grain of salt. Despite some weather geekiness, IANAM—I am not a meteorologist.)