29. There are two interesting charts that I wanted to post to my blog.
My parents have been keeping snow records since the year 2000, and I had an opportunity to enter the data into Excel and chart it.
The first chart (to the left) is yearly snow fall totals for the last seven years, from October 2000 until April 2007. When the current snow season ends, I will add that data to this chart.
For the location that these snow fall numbers have been measured, the National Weather Service's map of average seasonal snowfall shows 70 inches to be average. Four of the last seven years have been above average (57%) while the other three have been below average (43%).
Another interesting pattern has been the ups and downs in alternating years. By following the pattern, this year (2007-08) should be greater than 54 inches. I'm excited to find out.
Finally, I am surprised by the trendline (the dashed line). This trendline shows a overall decrease in snow fall amounts since 2000, by a decreasing slope of almost 5%. However, the R value is only 0.28, and it's clear by looking at the chart that the the snow fall totals are quite variable. Again, I'm excited to add this year to the chart to see how it compares and changes the trendline.
As I continued to data-mine, I found notes of when the first and last snows were recorded. This data carries less weight since snowflakes mixing in with snow are the result of many variables, but interesting none-the-less.
On this second chart (to the right), the lower red line shows dates on which the last snowflakes fell from the sky in Spring. The upper blue line shows dates on which the first snowflakes fell from the sky in Autumn. I have added dashed trendlines to both sets of data.
The slope of the upper trendline is very near zero (0.17%) but the slope of the lower trendline shows greater change (6.9%). This year's Spring data will be interesting to compare, but since 2000 it appears that the the last snowflakes are falling from the sky later into the Spring.
Averaging the dates produces April 16th as being the mean date that snow ends, and October 27th as the first date snow begins falling. Of course, it usually takes several weeks for the precipitation to turn completely over to snow and being accumulating on the ground, and vise versa in the Spring.
Looking at this second chart has given me an idea of adding the dates of when the precipitation begins and ends as only snow - a future project.