Since this topic came up in various threads, I wasn’t sure where to post it, so I just made a new topic altogether. I looked up all the snow events that were 1” or more over the last 40 years at BWI and DCA (1980-2019) and charted them. An event was defined as 1” or more within a 3-day period. In some cases there was accumulating snow on four consecutive days- those were treated as two events, since NWS does not recognize 4-day snow events.
Surprisingly for BWI, the trend line was slightly positive. On average, there are about 4-5 snow events of 1” or more during the season at BWI.
For DCA, the trend was slightly negative. On average, there are about 3-4 snow events of 1” or more during the season at DCA.
The year-to-year volatility for both locations started to increase from the mid-90’s onward. One other thing is that the number of events does not always correlate to whether the overall season was above or below average in total snowfall. For example, 2001 had below average snow and 2016 had above average snow; however, 2001 had more events than 2016.
1” was just an arbitrary line in the sand- perhaps if I raised or lowered the threshold, the story would be completely different. But the main topic on the forum recently has been (for example) that a 2” event would now be 0.2”. This chart should capture a decrease in those situations.
@psuhoffman @North Balti Zen and @RevWarReenactor may be interested in this. Feel free to discuss or poke holes in it. It was a cursory look, but I can dig deeper if there's something more that anyone is interested in. Although I would ask that anyone please ask my permission first if they want to copy the charts to another site, thanks!